Radiation oncology physics ABR

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What portion of the GI tract absorbs most nutrients

Ilium

Most likely outcome of 1 Gy gonadal irradiation

Temporal infertility

What is the "edge effect" or the "tissue lateral damage" in treating multiple beams

The biologic effect in the normal tissue is greater if it receives alternating high and low dose fractions compared with equal but medium size dose fractions

Podgorsak: formula and value of Compton wavelength

Lambda<sub>C</sub> = h/(m<sub>e</sub>c = 0.024 Angstroem

TG-51 formula for fully corrected charge reading from ion chamber

M=PionPTPPelecPpolMraw

Best technique for imaging multiple sclerosis

MRI

What technique maps magnetic field created by brain activity

Magnetoencephalograpy (MEG)

Khan: method recommended by Khan for finding effective SSD in electron field

Measure dose in phantom at dmax for 0 air gap between phantom and applicator (I_0). Next measure dose for air gap >0 (I_g). Since (I_0/I_g) = (VSSD + dmax +gap)^2/(VSSD + dmax)^2, plot sqrt(I_0/I_g) vs gap, slope of the curve gives VSSD.

Def: radiation weighting factor

Measure of the relative radiosensitivity of each orgain for the induction of stochastic effects

TG-75 def: CTDI<sub>w</sub>

Measurement estimate of CTDI<sub>100</sub>. It represents a weighted average of the dose in the center and periphery of a patient's body

Huda: how is 99mTc obtained from 99Mo

Mo is not soluble in saline and Tc is, so saline is ran though a column to wash off 99mTc in the form of sodim pertechnetate

X-ray target materials for mammography imaging and why

Molybdenum and Rhodium because have characteristic x-rays around 20 keV which provide best contrast for breast imaging

TG-51 relation between dose to water calibration factor in beam quality Q and 60Co

NQD,w=kQN60CoD,w

Huda: US body regulating radiation protection

National Committee on Radiological Protection and Measurements (NCRP)

1 Gy to whole body causes what syndromes

Nausea and Vomiting

Unfold the abbreviation NTCP

Normal Tissue Complication Probability

Huda: US body responsible for the rules and regulations regarding nuclear materials

Nuclear Regulatory Commission (NRC)

Hendee: def oxygen enhancement ratio

OER = (dose required to achieve specific biological effect with no oxygen present)/(dose required for the same effect given partial pressure of oxygen)

TG-51: point of measurement for a cylindrical chamber

On the central axis of the chamber. Used when measuring dose at an individual point (as opposed to a depth-dose curve).

Formula for power radiated from an X-ray tube with Z anode material, potential V and current I

P [W] = 0.9 x 10^-9 (atomic number) (tube voltage [V])^2 (tube current [A])

Formula for Poisson distribution given the average is A and random variable N

P(N,A) = A<sup>N</sup>/N! exp(-A)

Formula for Normal distribution given average A, standard deviation S, and random variable X

P(X,A,S) = 1/(sqrt(2Pi)*S) * exp(-0.5*((X-A)/S)^2)

Stats: (binominal) given success probability p and n trials, what is the probability of getting x successes

P(x) = n!/((n-x)!x!) * p^x*(1-p)^(n-x)

What type of scan is used to stage lung cancer

PET

TG-51: formula for PQgr for cylindrical chambers in electron beam

PQgr = (ionization reading at dref + 0.5rcav)/(ionization reading at dref)

TG-51: formula for PTP

PTP=(273.2+T)/(273.2+22.0)x101.33/P

The ideal gas law formula

PV = nRT where R is Rydberg constant (universal gas constant)

Title of TG-142

QA of medical accelerators

TG-21 def: Betawall

Quotient of absorbed dose to collisional kerma in the wall under the conditions of transient electronic equilibrium (Error in TG-21: Awall already includes Betawall)

Rydberg constant (universal gas constant) value

R = 8.314 J/(mol*K)

Rule of thumb for R50 in electron beam

R50 (cm) = E (MeV) / 2.33

Formula for the definition of RBE

RBE = (Dose of reference radiation required to produce a particular response)/(Dose of radiation in question required to produced the same response)

Varian VMAT product name

RapidArc

Def: wedge (transmission) factor

Ratio of doses with and without the wedge at a point in phantom along the central axis of the beam past Dmax (e.g. 10 cm)

TG-21 def: Prepl

Ratio of photon energy fluence at the center of the cavity when the cavity is filled with medium to that when the cavity is filled with air. Also ratio of electron fluences with and without the cavity.

KHAN: formula for SMR using TMR

SMR(d,rd) = TMR(d,rd)(Sp(rd))/(Sp(0)) - TMR(d,0), where Sp is phantom scatter factor and rd is field size at depth d

Major source of radiation to the radiographer during fluoroscopy procedure

Scatter from patient

manufacturer of the linac with the virtual wedge

Siemens (out of business)

Formula for pressure at depth

(pressure) = (density) * g * (depth)

Dmax value for 60-Co

0.5 cm

Compton interaction probability change with photon energy

1/E

Rule of thumb: energy loss per 1 um of tissue by alpha particle

100 keV

1 atm in psi

14.695

Formula for maximum number of electrons per orbit

2n2

Co-60 half life

5.26 y

Huda: ICRP 60 lifetime whole body limit for nuclear woker

<0.8 Sv

TG-51: describe procedure for measurement of electron beam quality specifier (R50)

>=10x10 cm2 (>=20x20 cm2 for R50>8.5 cm, i.e., >20MeV) field size, 100 cm SSD, correct the measured depth ionization curve by shifting 0.5rcav upstream , find 50% (called I50), use TG-51 formula 16 to find R50.<br>Alternative: use diode detector or convert depth ionization curve to pdd.

What type of tumor will show up brightest on a CT scan

Bone (osteosarcoma)

Anat: larynx is close to what vertebra

C6

Hendee rad safety: relation between DAC and ALI

DAC = ALI/(2.4 x10^9 mL)

Rule of thumb equilibrium field size as function of energy

FS (cm) = E (MeV) / 2

def: TVL

Thickness of a material required to attenuate the beam by 90%

what is thyratron and what is its function in linacs.

Thyratron high voltage switch. In linacs it is the hydrogen thyratron that provides a few microsecond flat top DC pulses to the electron gun as well as magnetron or klystron

2 differences between electromagnetic and ultrasound radiation of a given frequency

[1] EM are transverse waves, US longitudinal [2] US requires a medium

Radioactivity: name 4 radioactive decay series

[1] Thorium [2] Neptunium (decayed already) [3] Uranium [4] Actinium

Huda: 3 groups of subjects where carcinogenic effect of radiation was studied

[1] radium dial painters [2] uranium miners [3] atomic bomb survivors

Def: transient equilibrium

half-life of the parent is comparable with half-life of the daughter

Anat: name of a tumor in the tissue surrounding the brain

meningioma

Huda: how do 2nd generation CT scanner work

single tube (narrow 10 deg fan beam), rotating detector array, translates across patient, then increment the angle and repeat

Huda: how do 3rd generation CT scanners work

single tube (wide fan beam), rotating wide detector array, rotation only (no translation required)

Hendee: what is doubling dose

the amount of an agent (e.g. ionizing radiation) to double the spontaneous mutation rate in population

TG-51 def + formula: dref in electron beams

the reference depth for electron beams given as dref=0.6R50-0.1, where R50 is in cm. Unit: cm.

Huda: how is high contrast resolution of an image estimated

using a parallel line bar phantom

Khan: what is "field equivalence" in electron therapy

"field equivalence" means that for the same incident fluence and cross-sectional beam profile, the equivalent fields have the same depth dose distributions along the central ray

KHAN: formula for Mayneord F factor

((SSD2 + dmax)/(SSD1 + dmax))2 ((SSD1 + d)/(SSD2 + d))2

2 effects that may contribute to the chamber polarity effect

(1) Compton current - electrons independent of E-field (2) Extracameral current - current collected outside the sensitive volume

2 reasons why transient electron equilibrium exists in megavoltage beams

(1) attenuation of the photon beam (2) predominantly forward motion of the electrons)

KHAN: list 3 factors that influence photon pdd in water

(1) beam quality (2) field size and shape (3) SSD

KHAN: 6 parameters that affect isodose distribution

(1) beam quality (2) source size (3) beam collimation (4) field size (5) SSD (6) source to diaphragm distance (SDD)

Khan: 4 criteria for selection of ICRU reference point for target dose calculations

(1) dose to the point should be clinically relevant and representantive (2) should be easy to define (3) where the dose can be accurately calculated (4) not in penumbra or steep dose gradient

LI: 3 disadvantages of radiographic film

(1) energy dependent (2) developing temperature dependent (3) not tissue equivalent

TG-75: 3 methods of dose reduction and optimization in IGRT

(1) field collimation (2) pulsed fluoroscopy (3) nonradiographic imaging and hybrid imaging/tracking

TG-75: summary of 6 TG-75 recommendations

(1) list all IGRT procedures in use (2) identify steps that can be accomplished without ionizing radiation (3) reduce FOV where possible (4) plan for imaging technique be adequate to treatment decision being made (5) use TG-75 to estimage total patient IGRT dose (6) evaluate the dose for stochastic and deterministic risk

2 reasons for the stem effect in ion chambers

(1) measurable ionization in the body of the stem (2) ionization of the air between the end of the chamber and the metal cap

list 6 desirable chamber characteristics

(1) minimal variation of exposure measurement with photon energies (2) suitable volume for the expected range of measurements (3) minimal variation in sensitivity with the direction (4) minimal stem leakage (5) can be calibrated against a standard for exposure in radiations of different qualities (6) minimal recombination losses

LI: 5 disadvantages of TLD

(1) not real time (2) read-out and calibration time consuming (3) susceptible to structural damage (4) limited accuracy (3%-5%) (5) limited spatial resolution

KHAN: tissue-equivalent materials or phantoms (for photon beam) must have 2 features

(1) same effective atomic number (2) same electron density

LI: 3 disadvantages of diode

(1) slight energy dependence (2) directional dependence (3) minimal volume averaging effect

LI: 7 advantage of TLD

(1) small size (2) large dose range (3) linearity of response (4) no need for cables (5) tissue equivalence (made of e.g. LiF or LiF:Mg,Ti) (6) reusable (7) available in various forms

LI: 6 advantages of the diode

(1) small size (2) no external bias (3) rugged design (4) independent of air pressure (5) results immediately available (6) inexpensive

KHAN: size of geometric penumbra depends on 3 parameters

(1) source size (2) distance from the source (3) diaphragm distance

KHAN: 2 factors that contribute to the field flatness at depth

(1)) hardening the center of the beam due to the flattening filter (2) side scatter

Formula for electron density

(Avogadro)(Z/A)*(density) [electrons/cm3]

Handee: Formula for isocenter dose rate given: isocenter depth d, field size, calibrated dose rate at SSD and dmax, Sc, Sp, and F (transmission factor for all beam-modifying devices)

(Isocenter dose rate at d) = (Calibration dose rate at SSD and dmax)((SSD+dmax)/SAD)^2 TMR(FS, d) Sc(collimator FS) Sp(patient FS) F

Hendee: Empirical formula for the ratio of radiative to collisional energy loss by an electron of energy E in the medium of atomic number Z

(Radiative energy loss)/(Collisional energy loss) = EZ/820

def: exposure

(absolute value of the total charge of the ions of one sign proudced in air when all the electrons liberated by photons are completely stopped) / (the mass of air)

Hendee rad safety: formula for attenuation factor of shielding material that must be provided

(attenuation factor) = Xp * d^2/(WUT), where Xp is maximum permissible level (0.1 or 0.01 R/week), d is x-ray tube distance to the wall in meters, W is work load in R-m^2/(mA-min)*(mA-min)/week, U is use factor (1,1/4,1/16), T is occupancy factor (1,1/4,1/16)

Formula for average error of digitization given analog range Ra and n bit ADC

(average error) = Ra/(2^(n+1))

Anat: which type of brain tissue shows bright on T1 weighted image

(bright==short T1 on T1 weighted image): fat, paramagnetic agents (Gd), subacute blood. Most brain pathology has long T1 (and T2)

MRI: given a chemical shift in ppm and magnetic field strength what is corresponding change in resonance frequency

(change in frequency [Hz]) = (chemical shift [ppm])*((gyromagnetic ratio [MHz/T])*(Magnetic field strength [T])) x10^6

Stats: formula for coefficient of variation

(coefficient of variation) = (standard deviation)/(mean)

Hendee def: Average Dose Equivalent for a population

(collective dose equivalent)/(number of individuals in population), unit [Sv]

Ultrasound attenuation coefficient as function of depth and frequency

(dB/cm) = 0.5 dB / cm /MHz

Huda (ultrasound): formula for acoustic impedance

(density)*(velocity of sound)

Huda (ultrasound): formula for Fresnel zone

(diameter of the transducer)^2/(4*wavelength)

Huda (ultrasound): formula for Doppler frequency shift

(frequency shift) = 2 (ultrasound frequency) (speed of the moving object) / (velocity of sound) cos(angle between the beam and moving object)

Podgorsak: relation between macroscopinc interaction coeffcient and atomic interaction coefficient (cross-section)

(macroscopic) = (cross-section) * (density) * (Avogadro) / (molar mass)

Formula for TERMA

(mass attenuation coefficient)(energy fluence)

def: (absorbed) dose

(mean energy imparted by ionizing radiation) / (material mass)

Given mass fraction of two materials f1 and f2 with mass attenuation coefficients mu1 and mu2, what is the total mass attenuation coefficient for the mixture

(mu/rho)_total = 1/100(f1*(mu/rho)1+f2*mu/rho)2)

Ultrasound: general formula for Doppler observed frequency (no assumption that SOS is much greater than speed of the source motion)

(observed frequency) = (velocity of sound)/((velocity of sound)+(radial component of velocity of the source))*(Source frequency)

Hendee: formula for quasithreshold given mean lethal dose and extrapolation number

(qualithreshold dose) = (lethal dose) * ln(extrapolation number)

Formula for resistance of the wire given resistivity, length, and cross-sectional area

(resistance) = (resistivity)*(length)/(cross-sectional area)

Radioactivity: formula for specific activity given half-life and atomic mass

(specific activity) = ln(2)/(half-life)*(Avogadro number)/(Atomic mass)

def: kerma

(sum of the initial kinetic energies of all the charged particles liberated by uncharged particles) / (material mass)

Radioactivity: what is the probability that a single atom survives a given time without decaying

(survival probability) = exp(-(decay constant)*(time))

Formula for surviving fraction assuming linear survival curve

(surviving fraction) = exp(-(radiation dose delivered)(slope of survival fraction curve))=exp(-(radiation dose delivered)/(mean lethal dose)) where mean lethal dose

Hendee: formula for maximum temperature rise from a given SAR

(temperature rise) = (Specific absorption rate)*(exposure time)/(heat capacity)

Radioactivity: formula for total number of nuclei in the sample given initial activity and average life

(total number of nuclei) = (initial activity)*(average life)

Radioactivity: true count rate for noparalyzable counter

(true count rate) = (recorded count rate)/(1 - (total dead time)) = (recorded count rate)/(1-(recorded count rate)*(dead time per pulse))

Radioactivity: true count rate for paralyzable counter

(true count rate) = (recorded counte rate)*exp(-(dead time per pulse)*(recorded count rate))

LI def: conformity index

(volume covered by prescription isodose line)/(volume of the target)

Beam active Linac head components order in electron mode

(x-ray target retracted), primary colimator, scattering foil on carousel, ion chamber, secondary collimator (fully open), electron applicator in accessory mount

Huda: Hounsfield Unit of air

-1000

Huda: Hounsfield Unit of water

0

Hendee: range of quasithreshold values for mammalian cells

0 to 6 Gy

Radioactivity: electron mass in amu

0.000549

KHAN: TAR is independent of distance from the source within the accuracy of ...

0.02

Typical effective dose in chest radiograph

0.02-0.05 mSv

Average photon energy for Pd-103

0.021 MeV

Average photon energy for I-125

0.028 MeV

TG-51: action level for polarity correction

0.03

Huda: approximate dose below which any radiation risks are deemed low comparing with normal risk of pregnancy

0.1 Gy

Skin absorbed dose in a typical AP chest radiograph

0.1-0.2 mGy

Typical effective dose in skull radiograph

0.1-0.2 mSv

Rule of thumb: doubling the current has the same effect on film darkening as increasing voltage by what percentage?

0.15

Huda: percentage of woman deaths attributed to breast cancer in US

0.18

TG-51: water tank maximum side wall thickness that can be neglected and not scaled to water-equivalent thickness

0.2 cm

TG-51: accuracy of the Pion formula for pulsed and pulsed-swept beams with VH/VL=2

0.2% for pulsed and 0.4% for pulsed-swept

Huda: annual effective dose from nuclear fallout weapons testing

0.3 % of annual dose

Huda: annual effective dose from cosmic rays

0.3 mSv/y

Huda: annual effective dose from external gamma rays

0.3 mSv/y

Huda: range of LETs for X-rays

0.3 to 3 keV/um

Huda: percentage incidence of breast cancer as fraction of all cancers in women in US

0.32

Average photon energy for Ir-192

0.38 MeV

Huda: annual effective dose from internal gamma rays

0.4 mSv/y

Average photon energy for Au-198

0.412 MeV

Huda: dose threshold for deterministic effects

0.5 Gy

Huda: K-shell binding energy for Oxygen

0.5 keV

Rule of thumb: energy loss per 1 um of tissue by electron or positron

0.5 keV

Huda: max monthly dose to fetus of a nuclear worker

0.5 mSv/month

Typical effective dose in abdominal radiograph

0.5-1.5 mSv

TG-51: effective point of measurement depth dose shift for a cylindrical chamber in electron field

0.5rcav upstream

Hendee: average annual total equivalent dose from man-made background

0.6 mSv

KHAN: beam quality for maximum BSF

0.6 to 0.8 mm Cu, depending on field size

Average photon energy for Cs-137

0.662 MeV

value of ln(2)

0.693

TG-51: effective point of measurement depth dose shift for a cylindrical chamber in photon field

0.6rcav upstream

Huda: ICRP estimate of severe hereditary effects per Sv of gonadal irradiation for workers

0.8 %/Sv

Average photon energy for Ra-226

0.83 MeV

Average photon energy for Rn-222

0.83 MeV

1 Angstrom in meters

1 A = 10E-10 m

1 Bq in Ci

1 Bq =~ 27 pCi

1 Ci in Bq

1 Ci = 3.7 x 10E10 Bq

1 Ci in GBq

1 Ci = 37 GBq

1 GBq in mCi

1 GBq = ~27 mCi

1 GBq in Ci

1 GBq =~0.027 Ci

1 Joule in ergs

1 J = 1 x 10^7 erg

megavoltage therapy energy region and treatment depths

1 MV or greater

Express 1 Mbit as a power of 2

1 Mbit = 2^20

1 Roentgen in C/kg

1 R = 2.58 x 10-4 C/kg

Show that 1R in air equals 0.876 cGy

1 R = 2.58E-4 C/kg * 33.97 J/C = 0.876 cGy

Huda (ultrasound): unit of acoustic impedance

1 Rayl = 1 kg/m^2/s

1 Tesla in Gauss

1 T = 10 000 G

1 U (AKS) in Si units

1 U AKS = 1x10E-6 Gy/m2/h (AKS=Air Kerma Strength)

1 atomic mass unit (1 amu) energy equivalence in MeV

1 amu is equivalent to 931 MeV

1 bar in kPa

1 bar = 100 kPa

1 calory in J

1 cal = 4.186 J

Huda (ultrasound) def: 1 dB

1 dB = 10 B = 10 log10(I/I<sub>0</sub>)

1 ft in m

1 ft = 0.3048 m

Huda (radiation protection): max leakage radiation from X-ray tube

1 mGy/hour at 1 m

Typical integral dose in a chest x-ray

1 mJ

US Nuclear Regulatory Commission public annual allowable dose

1 mSv

Huda: ICRP 60 dose to fetus limit for nuclear wokers

1 mSv (same as member of the public)

(MRI): typical change in the magnetic field strength accross a 20 cm FOV imaging volume when frequency encode gradient is applied for a typical SE sequence

1 mT

1 mile in km

1 mile = 1.609 km

1 rad in Gy

1 rad = 0.01 Gy

Definition of 1 rad

1 rad is 100 ergs of energy absorbed in 1 gram of matter

Huda (ultrasound): typical intensities of clinical ultrasound

1 to 10 mW/cm2

Podgorsak: strength ratio of the strong and weak force

1 to 10E-6

Podgorsak: strength ratio of the strong and electromagnetic force

1 to 137

Podgorsak: strength ratio of the strong and gravitational force

1 to 1E-39

Huda: range of ultrasound frequencies used in diagnostics

1 to 20 MHz

typical x-ray tube current in fluoroscopy

1 to 5 mA

Radioactivity: proton mass in amu

1.00731

Radioactivity: neutron mass in amu

1.0087

TG-51: maximum acceptable Pion (recombination correction) for a chamber

1.05

TG-51: PMMA water-equivalent ratio

1.12

60Co gamma energies

1.17 and 1.33 MeV

Density of air

1.225 kg/m3 = 0.001225 g/cm3

Average photon energy for Co-60

1.25 MeV

Radioactivity: half life of 40-K

1.25x10^9 y

Huda: ICRP estimate of severe hereditary effects per Sv of gonadal irradiation for whole population

1.3 %/Sv

Dmax value for 6 MV photon beam

1.5 cm

Skin absorbed dose in a typical AP skull radiograph

1.5 mGy

1 eV in J

1.602 x 10E-19

Proton mass in kg

1.67E-27 kg

Embryo dose as a fraction of skin dose for a typical lateral projection

1/20 of the skin dose (in direct beam)

Embryo dose as a fraction of skin dose for a typical Anterior-Posterior projection

1/3 to 1/4 of the skin dose (in direct beam)

Embryo dose as a fraction of skin dose for a typical Posterior-Anterior projection

1/6 of the skin dose (in direct beam)

Max dose to lens of the eye to avoid cataract

10 Gy

U.S. maximum legal limit for entrance skin exposure in fluoroscopy

10 Roentgen/min

Skin absorbed dose in a typical lumbar spine (lateral) radiograph

10 mGy

NCRP lifetime effective dose limit for occupational exposure

10 mSv x age

Huda: 13-N half life

10 min

Typical entrance skin dose (exposure) rates in fluoroscopy

10 to 100 mGy/min (1 to 10 Roentgen/min)

Huda: approx. effective hourly dose for space travel

10 uSv/h

Risk of cancer lethality by radiation per Sv delivered in high dose rate for whole population

10% per Sv

TG-51: SSD required when establishing beam quality for photon and electron beams

100 cm is required because %dd(10) and R50 are functions of SSD whereas absorbed-dose calibration factors are not (for 10x10 cm2 fields)

Typical integral dose in a head CT examination

100 mJ

typical x-ray tube current in radiography

100 to 1000 mA

Huda: Formula for Hounsfield Unit of a tissue

1000 * ((attenuation coefficient of a tissue) - (attenuation coefficient of water))/(attenuation coefficient of water)

Huda: Hounsfield Unit of cortical bone

1000+

1 atm in kPa

101.3 kPa

Huda: order of magnitude fluence that is needed to produce a radiographic image

10^5 photons/mm^2

Huda: 4 common PET radioisotopes

11-C, 13-N, 15-O, 18-F

Huda: 18-F half life

110 min

the number of thoracic vertebrae

12

Anat: number of cranial nerves

12 pairs

Radioactivity: half life of 3-H

12.3 y

Huda: isotope used for thyroid cancer therapy

131-I

Huda: ICRP 60 lens of the eye dose limit for nuclear worker

150 mSv/y

orthovoltage therapy energy region and treatment depths

150 to 500 kV (most operated at 200 to 300 kV), single beam less than 2 cm (90% pdd position), combining different angles gives a possiblity to treat lesions deeper than 2-3 cm.

Huda (ultrasound): average velocity of sound in soft tissue

1540 m/s

Ra-226 half life

1600 y

Pd-103 half life

17 days

Huda: isotope used for FDG tumor staging

18-F

TG-43: majority of brachytherapy treatments are done using these two isotopes

192-Ir and 125-I

How many temporal lobes does the brain have

2

Huda: annual effective dose from 222-Radon

2 mSv/y

Huda: 15-O half life

2 min

X-ray contamination of a 15 MeV electron beam (approx)

2-4 %

Huda: acute threshold dose for death from infection due to hematopoietic failure

2-7 Gy

def: 1 R is how many ion pair in 1 cm3 of air

2.08x10^9

Dmax value for 10 MV photon beam

2.5 cm

Au-198 half life

2.7 days

Huda: ICRP 60 whole body dose limit to nuclear worker

20 mSv/y

Huda: 11-C half life

20 min

TG-51: relative humidity admissible by the protocol and error introduced by its variations

20% to 80%<br>Ignoring humidity introduces +-0.15% error

Maximum exposure rate in high-dose fluoroscopy

200 mGy/min

Huda: isotope used for myocardial perfusion imaging

201-Tl

Huda: majority of background radiation comes from

222-Radon

Huda: most common alpha emitter in nature

226-Ra

standard temperature in inches of Hg

29.92

Hendee: max value of oxygen enhancement ratio for mammalian cells

3

Huda: American College of Radiology recommendation for maximum average glandular dose for a 4.2 cm thick breast

3 mGy

Skin absorbed dose in a typical abdominal radiograph

3 mGy

Depth for the lens dose equivalent

3 mm

Gestation period most prone to congenital anomalities

3 to 8 weeks after conception

speed of light in m/s

3 x 10^8 m/s

Lethal acute whole body dose (LD50) of photons for gumeans assuming no medical intervention

3-4 Gy

Dmax value for 15 MV photon beam

3.0 cm

Radioactivity: half-life of Tl-201

3.04 days

1 esu in C

3.34E-10 esu/C

Electron density of water (value in electrons/cm3)

3.34E23 [electrons/cm3]

Huda: total annual radiation dose in US

3.6 mSv/y

1 Ci in Bq

3.7 x 1010

Rn-222 half life

3.83 days

Huda: approx. effective dose from transatlantic flight

30 - 50 uSv

Cs-137 half life

30 y

TG-75: dose estimage from typical multiclice chest CT of average size

30-50 mGy

TG-51: minimum water tank dimensions for clinical reference dosimetry

30x30x30 cm3

Anat: number of spinal nerves

31 pairs

Huda: K-shell binding energy for Iodine

33 keV

KHAN: value of: (energy needed to create an ion pair in dry air)/(electronic charge)

33.97 J/C

Huda: ultrasound velocity in air

330 m/s

Normal volume of prostate

35 cc

Huda: K-shell binding energy for Barium

37 keV

Huda: minimum patient skin X-ray tube focus distance in fluoroscopy

38 cm

Huda: ICRP estimate of the percentage of fatal cancers per Sievert for working population

4 %/Sv

KHAN: formula for radius of a circle that is equivalent of a rectangular field

4 (area)/(perimeter) / sqrt(pi)

Huda: K-shell binding energy for Calcium

4 keV

What blood vessels has the highest concentration of oxygen in the body

4 pulmonary veins (2 from each lung)

Podgorsak: energy threshold for triplet production

4*511 keV

Huda (ultrasound): given two regions with Z1 and Z2, what is the transmitted intensity of US (at normal incidence)

4*Z1*Z2)/[(Z2+Z1)]^2

TG-142 updates this TG report #

40

contact therapy energy region and treatment depths

40 to 50 kV, less than 2 mm

Huda: fetal dose of 10 mGy in second or thrird trimester increases childhood leukemia risk by

40% (childhood leukemia is a relatively rare disease)

Huda: two radioactive isotopes in human body that deliver significant internal dose

40-K and 14-C

Huda (MRI): what is Larmor frequency of hydrogen at 1 Tesla

42.5 MHz.

Huda (MRI): what is the value of gyromagnetic ratio for hydrogen

42.5 MHz/T

What is the normal hematocrit level in men and women

46% in men, 38% in women

TG-75: another name for respiration-correlated CT

4D CT

the number of lumbar vertebrae

5

Huda: ICRP estimate of the percentage of fatal cancers per Sievert for whole population

5 %/Sv (higher than for working population because includes children)

Huda: US max dose to fetus of a nuclear worker

5 mSv (higher than ICRP 60 recommendation because a lower level would preclude women from seeking employment)

Huda: population congenital abnormality rate in US

5% of live births

Huda: acute threshold dose for permanent azoospermia

5-6 Gy

Hendee rad safety: when designing the thickness of radiation barriers for controlled areas, what is the target max dose limit on the other side of the barrier

50 mSv/y ~= 1.0 mSv/week

superficial therapy energy region and treatment depths

50 to 150 keV, less than 5 mm

Huda: acute threshold dose for death from cerebral edema

50-100 Gy

Huda: ICRP 60 extremities dose limit for nuclear worker

500 mSv/y

supervoltage therapy energy region and treatment depths

500 to 1000 kV, similar to 60-Co

Radioactivity: half life of 14-C

5700 y

I-125 half life

59.4 days

Huda: 99mTc half life

6 h

Huda: 99m-Tc isometric state half life and gamma energy

6 h, 140 keV

Dose needed for CNS syndrome

6-8 Gy

Minimum dose to induce CNS death

6-8 Gy

Planck's constant

6.62 x 10-34 m2 kg/s

Planck's constant in J s

6.626 x 10^-34 J s

Value of the gravitational constant

6.67 x 10^-11 N m^2/kg^2

KHAN: max energy where TARs and BSFs can be used

60Co. TARs and BSFs cannot be accurately measured for high-energy beams. TMRs (or TPRs) with Sc and Sp have to be used instead.

the number of cervical vertebrae

7

Huda: acute threshold dose for death from gastrointestinal failure

7-50 Gy

Ir-192 half life

73.83 days

1 atm in Torr

760

1 atm in mmHg

760

standard pressure in mm Hg?

760

Risk of cancer lethality by radiation per Sv delivered in high dose rate for working population

8% per Sv

Value of the Boltzmann constant in eV/K

8.6 x 10^-5 eV/K

Huda: alpha decay is most common in atoms with atomic numbers greater than ...

82

Huda: K-shell binding energy for Lead

88 keV

Electron mass in kg

9.11E-31 kg

TG-51: SSD limits for clinical clinical reference dosimetry

90 cm to 110 cm

Energy equivalent of 1 amu

931 MeV

Huda: parent nucleus of 99mTc and its half-life

99Mo, T1/2=67 hours

Maximum allowable linac jaws transmission

<2%

Maximum allowable linac MLC transmission when MLCs are used in addition to jaws

<5%

Radioactivity: formula for production of activity in neutron flux

A = (neutron flux) (number of target nuclei) (cross-section) (1 - exp(-lamda*(irradiation time)))

Podgorsak formula: given the decay: Parent -> Daughter -> Grand-daughter. What is the formula for activity of the Daughter as function of time

A<sub>D</sub>(t) = lambdaD/(lambdaD-lambdaP)*A<sub>P</sub>(0)*[exp(-lambdaP*t)-exp(-lambdaD*t)]

Power formula to estimate activity of a source after N half-lives

A=A02-N

Anat: what is neoplastic dysplasia

An abnormality in maturation of cells within a tissue (indicative of early neoplastic process)

Huda: what is DICOM

An image based medical protocol that speficies image formats

Hendee rad safety: definition of ALI

Annual Limit on Intake is the derived limit for the amount of radioactive material ingested or inhaled in a year

Podgorsak: describe behavior of mean energy transferred to electron as function of incident photon energy in Compton process

Around 1% at 10 keV increases to close to ~80% at 100 MeV

Podgorsak: describe behavior of maximum energy transferred to electron as function of incident photon energy in Compton process

Around 2% at 10 keV increases to close to ~100% at 100 MeV

TG-51: describe procedure for measurement of beam quality specifier (%dd(10)x) for photon E>10MV

At E>10MV electrons from accelerator head add to dmax thereby reducing %dd(10)x. Use the Pb foil to reduce electron contamination. Foil position 50 cm from phantom surface, thickness ~1 mm. SSD 100 cm. Correct the measured %ddPb for effective point of measurement (0.6rcav), use formula 13 from TG-51 to find %dd(10)x from %dd(10)Pb.

KHAN def and formula: backscatter factor

BSF = (dose on central axis at dmax)/(dose at the same point in free space) = TAR(dmax,rdmax), where rdmax is field size at dmax

TG-51: why effective point of measurement for a cylindrical chamber is not the same as point of measurement

Because of predominantly forward direction of the secondary electrons

TG-51: why well-guarded plane-parallel chambers are preferred for measuring electron beam depth-ionization curves

Because plane-parallel detectors minimize variations in the electron fluence correction factor

TG-51: why no shift of the point of measurement is needed for absolute dose measurement

Because the gradient effects photons are included implicitly in kQ and explicitly in PQgr for electrons, i.e., this formalism gives the dose to water at the point occupied by the point of measurement after the chamber is removed

TG-51: why there is no kQ info for photons in the protocol for plane-parallel chambers?

Because there is insufficient information about wall correction factors in photon beams other than 60Co beams

Competing process for electron capture

Beta+ decay

TG-75 def: CTDI

CT dose index represents the total dose deposited at a point within a single scan slice during a complete exam and allows for the fact that slices up and downstream from the slice will contribute dose to the slice in question.

What mineral is used by nerve cells to stimulate skeletal muscle

Ca

formula for value of the Chi^2

Chi^2 = 1/average*sum(value_i - average)^2 = (N-1)*sigma^2/average

Huda: highest contributor to medical exposure to ionizing radiation

Computed Tomography

Huda: state level coordinatory body for X-ray protection activities

Conference of Radiation Control Program Directors (CRCPD)

TG-21 def: Pwall

Correction factor that accounts for the difference between the composition of the chamber wall and the phantom (in user's beam)

Podgorsak: unravel the acronym CEMA

Coverted Energy per unit MAss

formula for relationship between dose and energy fluence at a point where transient electron equilibrium exists

D = (dose to collisional kerma) (mass energy absorption coefficient averaged over incident photon energy fluence) (energy fluence)

TG-51: formula for dose in electron beam

DQw=MPQgrk'R50kecalN60CoD,w

One charactersitic of TomoTherapy

Daily CT image collected in megavoltage beam (same X-ray source as the treatment) used for positioning

1 experiment that confirmed wave nature of matter

Davisson and Germer: intensity of electron statter from crystal surface formed constructive/destructive interference pattern as function of angle

Scattered radiation increases or decreases the wedge angle with increasing depth

Decreases

Hendee rad safety: definition of DAC

Derived Air Concentration is the in-air concentration that would result in ALI if breathed by a reference human for a year.

Treatment planning: unfold DMPO abbreviation

Direct machine parameter optimization

def: SAD

Distance from the source to the rotational axis of the machine

KHAN: Spencer-Attix version of Bragg-Gray formula for dose to medium when the cavity is small

Dmed = (charge of one sign per unit mass of the cavity gas)(energy to produce one ion pair)/(electron charge)(average restricted mass collisional stopping power for electrons)

KHAN: Bragg-Gray formula for dose to medium when the cavity is small

Dmed = (charge of one sign per unit mass of the cavity gas)(energy to produce one ion pair)/(electron charge)(weighted mean ratio of the mass stopping power of the medium to that of the gas for electron crossing the cavity)

TG-21: formula for dose to medium given M and Ngas

Dmed = Ngas (ratio of restricted collisional stopping powers for medium and gas) M Pion Prepl Pwall

formula for relation between dose and energy fluence at a point where full charged particle equilibrium exists

Dose = (energy fluence) (mass energy absorption coefficient averaged over incident photon energy fluence spectrum)

KHAN def: effective primary dose (linac)

Dose due to the primary photons as well as those scattered from the collimating system

TG-51: Pion depends on this in accelerator beams

Dose per pulse

roentgen to rad conversion factor for air under electronic equilibrium

Dose to air [rad] = 0.876 (exposure [Roentgen])

TG-43: title

Dosimetry of Interstitial Brachytherapy Sources

Anat: what type of breast cancer is most common

Ductal Carcinoma In Situ (cancer that sits in the ducts)

Huda: 123-I decay mode, half life, gamma energy, production mode

EC, 13 hr, 159 keV, cyclotron

Huda: 125-I decay mode, half life, gamma energy, production mode

EC, 60 d, 27 keV and 36 keV, reactor

Formula for total relativistic energy in terms of momentum and rest mass

E^2 = (pc)^2 + (m<sub>0</sub>c<sup>2</sup>)<sup>2</sup>

manufacturer of the linac with the universal wedge

Electa (60 deg)

Def: electron binding energy

Energy required to knock an electron out of its shell

Huda: common computed radiography phosphor material

Europium-activated Barium Fluorohalide (BaFBr)

What is the transport index for a package within radioactive material

Exposure rate at 1 m from the surface

radionuclide used to in PET

F-18

Anat: term that illustrates bone opening or hole

Foramen

Huda (MRI): how does Gd work as contrast agent

Gd provides relaxation mechanism for spin-lattice demagnetization, thus shortening T1

Spontaneous activity was discovered by ...

H. Becquerel

Huda: relation between attenuation coefficient and half value layer

HVL = ln(2)/(attenuation coefficient)

relation between Half Value Layer (HVL) and attenuation coefficient (mu)

HVL = ln(2)/mu

Bethe formula: approximate formula for excitation potential as function of atomic number

I [eV] = 11.5 * (atomic number)

Khan: in electron fields: why virtual SSD does not give accurate inverse square law corrections for extended SSDs under all clinical conditions

ISL corection with VSSD is accurate for large fields only. For small fields the ISL underestimates the change in output due to a loss of side-scatter equilibrium. Effective SSD is used for ISL correction instead of VSSD

For electron beams the surface dose increases or decreases with energy

Increases

Explain the difference between individualized and universal wedge

Individualized wedge requires a separate wedge for each beam width and aligns the thin end with the beam border. Universal wedge serves all beam widths and is positioned centrally for all field sizes.

relation between kerma (K) and energy fluence

K = (energy fluence) (energy transfer coefficient averaged over energy fluence of photons)

formula for collisional kerma

Kcol = (energy fluence) (mass absorption coefficient averaged over incident photon energy fluence)

formula for radiative kerma

Krad = (energy fluence) (mass absorption coefficient averaged over incident photon energy fluence) (g/(1-g)), where g is the average fraction of electron energy lost to bremsstrahlung

Anat: at what vertebral level is the caudal end of the spinal cord in adult humans

L2

Anat: Location of the umbilicus with respect to vertebral bodies

L3/L4

What level is the iliac crest

L4

What is the rationale for fractionation in radiation therapy

Less damage to normal tissue (tumors often lack repair mechanisms)

Common TLD material

LiF (reasonably tissue equivalent)

Most radiosensitive cell division phase

M phase

Radioactivity: given two isotopes M(A,Z) and M(A,Z+1), how to calculate if beta minus decay is possible from M(A,Z) to M(A,Z+1)?

M(A,Z)-M(A,Z+1)>0

Radioactivity: given two isotopes M(A,Z) and M(A,Z-1), how to calculate if beta plus decay is possible from M(A,Z) to M(A,Z-1)?

M(A,Z)-M(A,Z-1) -2*(electron mass)>0

TG-142: new technologies added in TG-142

MLC, asymmetric jaws, dynamic and virtual wedges, EPID

TG-51: action required when polarity correction is bigger than 3% from 1 in 6MV photon field.

Must establish what polarity correction was in the calibration laboratory beam. If considerable, then redefine N60CoD,w as follows: <br> N60CoD,w = N60CoD,w / P60Copol

Formula for number of electrons per gram

N0 = NAZ/Aw

Meaning of V10<40% dose tolerance for lung

No more than 40% of the lung to receive 10 Gy

Def: optical density of a film

OD=log10((intensity of light incident)/(intensity of light transmitted through the film))

Typical dose prescription to prostate

Phase 1: 46 Gy, 2 Gy/fx, Phase 2: 32 Gy, 2 Gy/fx

Unfold the abbreviation: PACS

Picture Archiving and Communications Systems

TG-51: formula for Pion in pulsed or pulsed-swept beams

Pion(VH)=(1-(VH/VL))/(MHraw/MLraw-(VH/VL))<br>VH-> normal operating voltage<br>VL-> voltage reduced by at least a factor of 2

TG-51: formula for Pion in continuous beams

Pion(VH)=(1-(VH/VL)2)/(MHraw/MLraw-(VH/VL)2)<br>VH-> normal operating voltage<br>VL-> voltage reduced by at least a factor of 2

What gland controls endocrine system

Pituitary gland

Treatment planning: unfold PRV abbreviation

Planning organ at risk volume

TG-51: polarity correction formula

Ppol=abs((M+raw-M-raw)/(2Mraw))

TG-75 def: CTDI<sub>100</sub>

Practical implementation of CTDI. Air Kerma to one slice averaged over a scan length of 100 mm.

Electa VMAT product name

PreciseBeam Infinity

TG-21 origin of Prepl

Prepl arisies as a result of the displacement of the effective point of measurement of the chamber and its value depends on the depth dose gradient

Relation between primary dose and collisional kerma past Dmax

Primary Dose = exp((attenuation coefficient)*(average distance between energy launch and deposition))*(Collisional kerma) =~ (1+(attenuation coefficient)*(average distance between energy launch and deposition))*(Collisional kerma)

Huda (MRI): from where does magnetization vector arise in tissue in strong magnetic fields

Protons align their spins up or down in external magnetic field. Spin up has somewhat more energy so slightly less protons align this way. Net magnetization remains from unpaired protons.

Def: TERMA

Quantifies all energy removed from the primary neutral beam

Rule of thumb for R80 in electron beam

R80 (cm) = E (MeV) / 3

Rule of thumb for R90 (therapeutic range) in electron beam

R90(cm) = E (MeV) / 4

Khan: minimum field size radius in electrons to achieve lateral uniformity

R_eq [cm] = 0.88 sqrt(E [MeV])

Def: entrance skin dose

Radiation absorved dose by the skin resuling from skin exposure

Def: entrance skin exposure in a radiologic examination

Radiation exposure incident on a patient

What is radiation leakage of a linac

Radiation other than intended

Rule of thumb for Rp (practical range) in electron beam

Rp(cm) = E (MeV) / 2

given gross count rate CPM_G collected for TG and background count rate CPM_B collected for TB, what is the error S of the net count at 1 sigma

S = sqrt((RelativeError(CPM_G)^2 + RelativeError(CPM_B)^2) = sqrt( (sqrt(GrossCount)/TG)^2 + (sqrt(BKGCount)/TB)^2 = sqrt(CPM_G/TG+CPM_B/TB)

Most radioresistant cell division phase

S phase

KHAN: formula for SAR using TAR

SAR(depth, field size at depth) = TAR(depth, field size at depth) - TAR(depth, 0 field size)

Formula for surviving fraction on a linear portion of the SF curve assuming multitarget model (extrapolation number > 1)

SF = (number of surviving cells)/(initial number of cells) = 1 - (1 - exp(-Dose/D0))^(extrapolation number)

Hendee: Empirical formula for specific ionization of <10 MeV electron

SI = 45 (v/c)^2 Ion pairs per centimeter

KHAN: formula for SMR as function of Sp at reference depth of maximum dose (t0)

SMR(t0,rt0) = Sp(rt0)/Sp(0)-1, because TMR(t0,0) is unity by definition

KHAN: practical method of measuring phantom scatter factor Sp

Sp(field size) = Sc,p(field size)/Sc(field size)

KHAN formula: phantom scatter factor (Sp)

Sp(r)=BSF(given field size)/BSF(reference field size)

4 fundamental forces in Nature

Strong, Electromagnetic, Weak, Gravitational

In MRI when fat is bright and fluid shows dark the image is weighted with ...

T1

Hendee: the choice of TR primarily affects T1 contrast or T2 contrast in the image

T1 contrast

Huda (MRI): how do T1 and T2 times change with increasing magnetic field strength

T1 generally increases (hundreds on ms) T2 are approx. independent (tens of ms)

In MRI when fat is intermediate-bright and fluid shows bright the image is weighted with ...

T2

Hendee: the choice of TE primarily affects T1 contrast or T2 contrast in the image

T2 contrast

KHAN: formula for TAR(d,0) dependence on d past dmax

TAR(d,0) = exp(-(average attenuation coefficient)(d-dmax))

KHAN def: formula for TAR(d,rd)

TAR(depth, field size) = (dose at depth d in the phantom)/(dose in free space at the same point without the phantom)

Numbers of two TG reports describing brachytherapy

TG-43 (dosimetry of interstitial brachytherapy sources) and update of TG-43 (revised AAPM protocol for brachytherapy dose calculations)

TG-51: why plane-parallel chambers should not be used in reference electron dosimetry

TG-51 provides data for plane-parallel chambers but evidence exists that minor construction details significantly affect the response of these detectors in 60Co beams which makes kecal uncertain. Preferred is to cross-calibrate in high-energy electron beams against cylindrical chambers (see TG-39).

KHAN: formula for TMR change with depth for 0x0 field size

TMR(d,0) = exp(-(effective linear attenuation coefficient)((depth) - (reference depth of maximum dose))

Podgorsak: relation between tenth-value layer (TVL) and linear attenuation coefficient

TVL = ln(10)/(linear attenuation coefficient)

Relation between average life and half-life

Taverage=1.44T1/2

Relation between average life and decay constant

Tavg=1/lambda

radionuclide used for SPECT

Tc-99m

TG-51 def: Q

The beam quality in the user's photon or electron beam for which clinical reference dosimetry is to be performed. For photon beams it is given in terms of %dd(10)x and for electron beams, in terms of R50

TG-21 def: Awall

The correction factor that accounts for attenuation and scatter of photons in the wall and buildup cap of the chamber when exposed in air to 60Co beam

Anat: What is foramen magnum

The hole in the base of the skull through which the spinal cord passes

Def: tissue lateral effect for parallel opposed beams

The increase in central axis maximum dose near the surface relative to the midpoint dose.

TG-75 def: CTDI<sub>air</sub>

The same as CTDI<sub>100</sub> but measured without phantom so does not include backscatter. Directly comparable to "entraince air kerma"

Regulatory exposure rate level when the fluoroscopy system acquires images

There is no regulatory exposure level when the system is acquiring images

Unfold the abbreviation TCP

Tumor Control Probability

TG-51 conditions for the 3 terms when the following is true: DQw=MNQD,w

Under reference conditions:<br> DQW -> dose to water at the point of measurement of the ion chamber when it is absent (i.e. at the reference depth)<br>NQD,w -> dose to water calibration factor for the ion chamber in beam quality Q <br> M -> fully corrected electrometer reading corrected for ion recombination, polarity and electrometer calibration effects, and corrected to STP, and the same or equivalent waterproofing sleeve was used as in calibration

Radioactivity: 226-Ra belongs to which decay series

Uranium

For energy region where Compton dominates, how should medium density scaling be calculated

Using electron density, because Compton interaction probability depends on electron density

manufacturer of the linac with dynamic(later enhanced dynamic) wedge

Varian

LI: single focus MLC manufacturers

Varian, Elekta (rounded edge MLCs)

What distance should be used for distance correction in electron beam

Virtual SSD (smaller than nominal 100 cm SSD for photon)

unfold the abbreviation: VMAT

Volumetric Modulated Arc Therapy

Podgorsak: which particles transmit the wak force

W and Z<sup>0</sup>

relation between exposure and kerma

X = (collisional kerma in air) (electronic charge)/(energy required to produce an ion pair in dry air)

TG-21: formula for exposure measured in 60Co beam

X = (reading corrected for temperature and pressure) (ion chamber exposure calibration factor) (electrometer calibration factor)

Anat: female chromosome symbol

XX

Anat: male chromosome symbol

XY

formula for effective atomic number of a material in photon field

Zeff = (a1 Z12.94 + a2 Z22.95 + ...)1/2.94 (where an are fractional contributions of each element to the total number of electrons in the mixture)

Huda (ultrasound): given two regions with Z1 and Z2, what is the reflected intensity of US (at normal incidence)

[(Z2-Z1)/(Z2+Z1)]^2

Huda (MRI): describe the IR pulse sequence

[1] 180 deg pulse from Z to -Z [2] delay to allow for longitudinal relaxation (Inversion time - TI) [3] start SE sequence at TI to suppress tissues having T1=TI. Produces T1 weighted image with a selected suppressed tissue T1

Huda: 3 characteristics that make 99mTc most popular radionuclide

[1] 6 hour half-life [2] 140 keV photons [3] ready availability from a generator

Huda (MRI): describe the SE pulse sequence and signal formation

[1] 90 deg pulse from Z to Y [2] delay to allow transverse defocus [3] 180 deg from Y to -Y to allow transverse refocus [4] signal collection at echo time (TE)

Podgorsak: 8 main modes of producing vacancies in inner atomic shells

[1] Coulomb interaction with energetic charged particle [2] photoelectric [3] Compton [4] triplet production [5] electron capture [6] internal conversion [7] positron annihilation [8] Auger effect

Huda (MRI): 2 reasons why protons are good candidates for MRI

[1] abundant in the body [2] has large magnetic moment

4 ligaments of the knee

[1] anterior cruciate ligament (ACL) [2] posterior cruciate ligament (PCL) [3] Medial collateral ligament (MCL) [4] Lateral collateral ligament (LCL)

Huda (MRI): describe the GRE technique

[1] apply single RF pulse (may be low angle) [2] turn dephasing gradient on [3] reverse dephasing gradient polartity to cause rephasing

Anat: how is hiatal hernia diagnosed

[1] bariuim X-rays [2] endoscopy

Huda: 4 most radiosensitive organs of the body

[1] bone marrow [2] colon [3] lung [4] stomach

Hendee: 3 stochastic effects of radiation

[1] carcinogenesis [2] teratogenesis (induction of birth defects) [3] mutagenesis (induction of genetic disorders in future generations)

2 types of pituitary gland tumors

[1] carcinoma [2] adenoma

Anat: what organs are located at the axial level of the iliac crest

[1] colon (part of ascending, transverse, and descending) [2] small intestine (at the jejunum)

Anat: 4 functions of the liver

[1] detoxification [2] protein synthesis [3] bile production [4] metabolism

TG-142: 3 sections of daily QA

[1] dosimetry [2] mechanical [3] safety

TG-142: 4 sections of monthly and annual QA

[1] dosimetry [2] mechanical [3] safety [4] respiratory gating

beta decay occurs through 3 processes

[1] emission of negatron [2] emission of positron [3] capture of orbital electrons

Huda: 3 factors that affect resolution in radiography

[1] focal spot size [2] screen thickness [3] patient motion

Hendee: 6 types of MRI artifacts

[1] foreign objects [2] magnetic field inhomogeneity due to e.g. shim coils [3] gradient field nonlinearity [4] radio frequency e.g from outside noise [5] patient motion [6] chemical shift

Huda: 3 breast compression effects on the image

[1] greater sharpness [2] less scatter [3] reduced patient dose

Hendee: 3 subcategories of acute radition syndrome

[1] hematopoietic [2] gastrointestinal [3] cerebrovascular

Huda: 2 reasons why barium is a widely used contrast agent

[1] high atomic number [2] high physical mass density. Both increase PE absorption

Huda (MRI): 5 factors that increase SNR in MRI

[1] increasing slice thickness [2] decreasing image matrix size [3] reducing RF bandwidth during detection [4] increase magnetic field strength [5] increase the number of image acquisitions

Huda: 2 types of flat panel detector systems

[1] indirect [2] direct

Anat: blood flow through the heart

[1] inferior and superior vena cava to right atrium of the heart [2] atrium contracts, blood goes through tricuspid valve to right ventricle [3] ventricle contracts, blood goes through pulmonic valve to pulmonary artery [4] pulmonary vein to left atrium [5] atrium contracts, blood goes through mitral valve to left ventricle [6] ventricle contracts, blood leaves through aortic valve

Anat: what does the cerebellum control

[1] integration of sensory perception [2] coordination and motor control

4 factors that affect contrast in imaging

[1] intrinsic contrast [2] image technique [3] contrast agents [4] receptor contrast

Name 4 quantities that differentiate between particulate and electromagnetic radiation

[1] mass [2] speed [3] charge [4] size

Hendee: 5 bioeffects in MRI

[1] movement of ferromagnetic objects into the magnet [2] movement of implanted metallic devices [3] disruption of implanted devices [4] RF heating [5] induction of electrical currents within patient

Hendee: 6 factors that affect dose response of cells

[1] oxygen [2] LET [3] dose rate [4] fractionation [5] cell cycle [6] presence of radiation modifiers

TG-40: 3 daily QA components

[1] patient positioning (lasers, ODI) [2] patient dose (output constancy) [3] safety (door interlocks and audiovisual contact)

Uniformity of the dose distribution in parallel opposed beams depends on 3 paramters

[1] patient thickness [2] beam energy [3] beam flatness

2 original experiments that confirmed particulate nature of electromagnetic radiation

[1] photoelectric effect (idea: Einstein, performed by Millikan) [2] Compton effect

Huda: 3 steps needed to obtain a computed radiography image

[1] photons interact with phosphor and create latent image [2] plate is read-out using low energy laser to stimulate electron traps [3] high energy light is emitted which is measured using a photomultiplier tube

Hendee: 3 characteristics of stochastic effect of radiation

[1] probability of the occurence of the effect inclreases with dose [2] the severity of the effect in an individual is unrelated to the dose [3] there is no threshold below which the effect will not occur

3 reasons in electron beam to use bolus

[1] reduce range [2] even out entrance so to prevent irregularities in dose distribution [3] increase surface dose

Huda: 5 reasons to use compression in mammography

[1] reduce thickness (lower tube voltage can be used) [2] immobilization [3] spreads the tissue for easier lesions detection [4] brings image closer to image plane (reducing magnification and focal spot blur) [5] reduces exposure time minimizing patient motion

4 Rs of radiobiology

[1] repair[2] redistribution [3] repopulation [4] reoxygenation

TG-43 (brachy): 5 reasons for publication of the updated TG-43 report

[1] revised definition of air-kerma strength [2] alimination of --apparent activity-- for specification of source strength [3] elimination of anisotropy constant in favor of distance-dependent 1D anistropy function [4] guidance on extrapolating tabulated parameters for different distances [5] correction for inconsistencies and omissions

2 types of photoreceptors on the retina

[1] rods [2] cones

2 reasons why virtual SSD for electron is not the same as for photons

[1] scattering foil position is lower than the transmission target [2] electron scattering in air (electrons lose initial direction, the lower energy the closer is virtual SSD)

Huda: 3 characteristics of radiopharmaceuticals that limit patient dose

[1] short half life (compatible with duration and objectives of the study) [2] produce monochromatic photons (100 to 300 keV) [3] minimize production of particulate radiation

Huda: optimal size of the X-ray tube focal spot is determined by 2 factors

[1] small enough to produce sharp images [2] big enough to tolerate heat loading

Huda (MRI): 3 most commonly used pulse sequencies in clinical imaging

[1] spin echo [2] inversion recovery [3] gradient recalled echo

4 factors that affect image noise

[1] structure noise [2] radiation noise [3] receptor noise [4] quantum mottle

Celsius to Fahrenheit conversion formula

[C]*9/5+32

Huda (MRI): in image MRI formation: how are transverse positions on the image encoded

[X] additional small gradient along X is applied (read gradient) so resonance frequency varies with the gradient [Y] an additional short time gradient along Y is introduced before readout that introduces phase shift along Y

what is an isobaric transition

a decay process in which mass does not change

Huda: why is bowtie filter used in CT

a fan beam goes through shorter cord length of a human body at higher angles so the bowtie filter is used to reduce X-ray intensity at higher angles to minimize dynamic range of exposures at the detector

Hendee: what is quasithreshold dose

a measure of the shoulder width

def: center of electron production in megavoltage beams

a point upstream of dose depositoin point where the energy of photons is transferred to electrons

Huda (ultrasound): what is Q factor of a US transducer

a quantity that is related to frequency response of the transducer's crystal (low Q - produce wide range of frequencies)

Huda: how does indirect flat panel system work

a scintillation layer produces light which is detected by the next layer which is a 2D array of light detectors

Huda: what is photoconductor (used in digital imaging)

a solid-state device that detects x-rays directly

Anat: What is meiosis

a type of cell division in which daughter cells have half the number of chromosomes of the parernt cell

Huda def: spatial resolution

ability of an imaging system to resolve two adjacent high contrast objects

what does visual acuity of an observer describe

ability of the observer to extract detailed information from a small region of an image

Rule of thumb: lateral electron range in medium as fraction of forward range

about 1/3

the base of the original definition of Ci

activity of 1 g of radium

Original definition of 1 Ci was based on

activity of 1 gram of 226-Radium (or specif activity of 226-Radium)

LI: what is the cause of the tongue-and-groove effect

adjacent leaves extend into the field by different amounts

TG-51 def: P (pressure)

air pressure inside ion chamber. In a vented chamber it is assumed to be the same as the local air pressure. Not corrected to sea level, including temperature and latitude corrections for a mercury barometer. Unit kPa, reference 1013.25

Huda: what is the source of 222-Radon

alpha decay of 226-Radium (1620 y half life)

def: skin erythema dose

amount of x or gamma that produces reddening of the human skin

TG-51 def: Qecal

an arbitrary electron beam quality taken as R50=7.5 cm. It is introduced to simplify the factors needed in electron beam dosimetry. Equivalent for photons is the arbitrary 60Co field.

TG-43 (brachy): name at least 3 new quantities introduced in TG-43

anisotropy function, dose rate constant, geometry factor, radial dose function, air kerma strength

Hendee rad safety: what is a "controlled area"

any area where a yearly whole-body effective dose of 15 mSv or more could be delivered to an individual

Rule of thumb: given the maximum energy of beta electron, what is the mean energy

approx 1/3 of maximum energy

Podgorsak: photodisintegration threshold for deuteron and beryllium-9

approx 2 MeV

Huda: time to reach transient equilibrium between 99Mo and 99mTc

approx 24 hours

Thermal energy in eV

approx 25 meV

Huda: Hounsfield Unit of lung

approx. -300

Huda: Hounsfield Unit of fat

approx. -90

Huda: low end of dose for induction of cataract

approx. 2 Gy

Huda: the value of skin erythema dose

approx. 5 Gy

Huda: threshold dose for chronic cataract induction

approx. 5 Gy

thimble chamber wall thickness (or buildup cap) required to achieve electronic equilibrium for 60Co

approx. 5 mm

Huda: Hounsfield Unit of muscle

approx. 50

Huda: acute skin dose threshold for permanent alopecia

approx. 7 Gy

What is the circle of Willis

artery in brain that connects cerebral arteries which supply blood to brain

Hendee: how can be extrapolation number interpreted on the survival curve

as the average number of sensitive targets per cell

Where is the effective point of measurement for a plane-parallel chamber in an electron beam

at the front surface

Anat: where is the optic chiasm located

base of hypothalamus

Huda (MRI): why is image contrast in GRE dictated by T2* not T2

because rephasing is caused by reversal of the gradient so local magnetic field is affected by inhomogeneities

why megavoltage beams are not described using HVL

because the beam has already been hardened by the transmission target and further filtration does not change the beam quality

grentz-ray therapy energy region and treatment depths

below 20 keV, less than 1 mm

Particles emitted in beta decay

beta particle and antineutrino

Huda: 99-Mo decay mode and half life

beta-, 66 days

Huda: 131-I decay mode, half life, gamma energy, production mode

beta-, 8 d, 364 keV, fission product

TG-51 protocol energy range applicability for electrons

between 4 and 50 MeV

TG-51 protocol energy range applicability for photons

between 60Co and 50 MV

Anat: which organ produces red blood cells

bone marrow

People with multiple fluoro scans for TB have higher incidence of what cancer

breast

Huda: how is topographic (scout) image obtained

by advancing the patient couch trhough the gantry with the tube in a fixed position

TG-21 def: Ngas

calibration of the cavity gas in terms of absorbed dose to the gas in the chamber per unit charge or electrometer reading

What does cancer in-sity mean

cancerous growth confined to the site from which it started

Huda: two categories of stochastic effects

carcinogenesis and genetic damage

name of the cancer arising in epithelial cells

carcinoma

Anat: what artery supplies oxygenated blood to liver

celiac artery

Anat: what makes the gallbladder contract

cells of intestinal walls secrete hormone called cholecystokinin

schematic diagram of a chamber readout with op-amp in integrating mode

chamber anode to inverting op-amp input, non-inverting to groud, capacitor between inverting and op-amp output, system readout between op-amp output and ground

TG-51 def: kR50

chamber specific component of kQ in an electron beam which is independent of the ionization gradient at the point of measurement (i.e., kQ=kR50PQgr). kR50 is a function of the electron beam quality specified by R50.

Huda (ultrasound): what is US refraction

change in direction of US beam when it passes to a region of different acoustic velocity (Snell's law)

KHAN: Maynoard F factor accounts for change in PDD with SSD but not for ...

change in scatter

Huda: how does direcct flat panel system work

charge liberated in photoconductor is measured directly

Podgorsak def (stopping power): soft collision

charged particle passes an atom at a considerable distance, i.e. (impact parameter) >> (atomic radius)

Podgorsak def (stopping power): hard collision

charged particle passes an atom at short distance, i.e. (impact parameter) ~ (atomic radius), secondary electron forms a separate track

What is the critical target in the cell

chromosomes, because they contain genetic information required to function and reproduce itself

Components of the total interaction coeff for photons

coherent, photoelectric, Compton, pair production

Dependence of mass collisional and radiative stopping power on atomic number

collisional ~Z, radiative ~Z^2

Huda (MRI): what is lognitudinal magnetization

component of the net magnetization vector parallel to the magnetic field

Huda (MRI): what is transverse magnetization

component of the net magnetization vector perpendicular to the magnetic field

TG-51 def: standard environmental conditions

conditions (T+P+humidity) for which ion chamber calibration factors apply (22C, 101.33 kPa, 20%-80% humidity)

which type of photoreceptor can discrimiate light wavelength

cones

LI: rationale for rounded MLC leaf design

constant penumbra across the field

What is the coordinate system of PET

coordinate of the target image (e.g. CT)

what connects two hemispheres of the brain

corpus callosum

TG-40: recommended frequency of QA tests

daily, monthly, annual (no weekly)

Huda (MRI): what is T2*

decay of transverse magnetization that includes both: T2 and inhomogeneities of the main magnetic field (1/T2*=1/T2+1/T2inhomogeneity)

TG-51 def: reference conditions

defined conditions of depth, beam size and SSD/SAD for which clinical reference dosimetry is performed

Hendee def: what does the "committed" dose modifier mean

delivered by radioactive materials deposited internally within the body

Podgorsak: formula for change in photon wavelength due to Compton scatter

deltaLamda = (Compton wavelength)*(1-cos(photon scatter angle))

Anat: where is the hilum located

depression in tissue where arteries and veins attach

Huda (ultrasound): what information is presented in A mode

depth (X axis) intensity (Y axis), so shows position of interface only

What is Sestamibi scan used for

detection of hyperparathyroidism (abnormally high parathyroid hormone in blood)

TG-51 def: clinical reference dosimetry

determination of absorbed dose to water per MU under reference conditions in the clinic.

what is t-Student test used for

determining statistical significance of a difference between sets of measurements

what is chi-square test used for

determining the goodness of fit of measured data to an expected probability distribution

Huda: conceptual difference between stochastic and deterministic effects of ionizing radiation

deterministic effects occur after a given threshold, probability of stochastic effects increases with dose

def: stem effect in ion chambers

difference in reading whenever the length of the stem irradiation differes from that irradiation at the time of chamber calibration

Huda: main clinical role of ultrasound in mammography

differentiate cysts from solid masses

Huda (ultrasound) def: nonspecular reflection

diffuse scatter from irregular contours

Huda def: focal spot size of X-ray tube

dimension of the x-ray source as viewed from the image

Podgorsak: difference in ionization process by directly and indirectly ionizing radiation

directly: one step (Coulomb interaction with orbital electrons); indirectly: two steps (1) release of a charged particle in the medium (2) charged particles interactions through Coulomb interaction

3 reasons why skin dose is a poor indicator of patient radiation risk

does not take into account [1] exposed area [2] penetrating power of the x-ray beam [3] radiosensitivity of the exposed region

Low LET photon irradiation leading cell killing is mostly related to...

dose

Hendee rad safety: what is commited dose equivalent for an organ

dose accumulated in the organ over a 50-year period

KHAN def: total scatter factor (Sc,p)

dose rate at a reference depth for a given field size divided by the dose rate at the same point and depth for the reference field size

What is mean lethal dose on the surviving fraction curve

dose that delivers on average one lethal event per target, from Poisson distribution is the probability of not being hit when the average number of hits is 1 per target, so P(0) = 1^0/0!*exp(-1)

TG-40: dosimetric and spatial uncertainty level aimed by the TG-40 protocol

dosimetric uncertainty of +-5% and spatial uncertainty of +-5 mm

Huda (MRI): why do protons and neutrons have magnetic dipole

due to nuclear spin and internal charge distribution

Anat: what is the sequence of the three parts of the small intestine

duodenum, jajenum, ileum

Base of natural logarithm

e=2.718

Huda: the most likely result of a major radiation exposure duing first 10 days after conception

early intrauterine death

1 advantage of the individualized wedge system

economizes system output

What is a negatron

electron which originates from nucleus

Podgorsak: particles emitted in triplet production

electron-positron pair + an orbital electron

Name for a blood cloth that travels through bloodstream

embolus

Huda (ultrasound): what are US contrast agents made of

encapsulated microbubbles containing gases

Huda: what are cosmic rays

energetic protons and alphas (10^10 to 10^19 eV) which originate in galaxies

def: for a given nuclear reaction (or decay): what is a Q value

energy released during the transformation

blooming effect in x-ray tubes

enlargement of focal spot size with current owing to repulsion of adjacent electrons

TG-51 primary purpose of the dosimetry protocol

ensure uniformity of reference dosimetry in external beam radiation therapy with high-energy photons and electrons. Ion chambers calibration traceable to national standards of absorbed dose to water (NIST, NRCC, and ADCL)

Anat: what guards the entrance of the glottis and prevents food or liquid from going into the trachea

epiglottis

The earliest detectable deterministic sign of excessive skin dose is

erythema

If a patient was exposed to radium, where will radon be detected

exhaled air

What is extrapolation number on the survival fraction curve

extrapolation of the straight portion of the SF curve back to the dose=0 axis

TG-21 def: Pwall

factor that accounts for perturbation caused by the chamber wall being different from the phantom medium

Huda def: vignetting distortion in image intensifiers

fall-off in brightness at the periphery of the image intensifier field

Huda (ultrasound): what is Fraunhofer zone

far field of US beam

Huda: method of estimation of fetus dose using skin dose

fetus dose = 1/2 skin dose (accounts for skin attenuation)

KHAN: BSF depends on 2 factors

field size and beam quality

Anat: function of spleen

filters blood as part of immune system, recycles red blood cells; platelets and white blood cells are stored there

Huda: most vulnerable gestation period for radiation-induced congenital abnormalities

first trimester, 20 to 40 days after conception

TG-43 (brachy): old protocol was based on fluence in air. what was the problem associated with this?

fluence in air can be reliably determined for a point source. Actual sources show considerable anisotropy.

formula for fmed (or f-factor) in calculation of dose to medium

fmed = 0.876 (mass energy absorption coefficient averaged over photon energy fluence for medium)/(mass energy absorption coefficient averaged over photon energy fluence for air)

TG-51: which detector type should be used for clinical reference dosimetry

for R50≤4.3 cm (≤10 MeV) plane-parallel chambers are preferred<br>for R50≤2.6 cm (≤6 MeV) plane-parallel chambers must be used

TG-51: SSD must be 100 cm for clinical reference dosimetry or beam quality specification?

for beam quality specification

TG-51: methods of clinical reference dosimetry dosimetry at depths other than 10 cm for SAD setups

for dmax use clinical TMRs, for other depths use clinical TPRs

Huda def: linear attenuation coefficient

fraction of incident photons removed from the beam in traveling unit distance

Podgorsak def: restricted stopping power

fraction of the collisional stopping power that includes all collilsions which result in delta rays with energies less than a cut-off value (usually 10 keV in radiation dosimetry which is enough to traverse 1 mm gap of air)

Huda (radiation protection): def: occupancy factor

fraction of time people work on the other side of the barrier

Huda (radiation protection): def: use factor

fraction of time that radiation points in a specified direction

TG-51 def: M

fully corrected ion chamber reading corrected to the standard environmental conditions of temperature and pressure for which the ion chamber calibration factor applies; and also corrected for polarity effects, lack of complete ion collection efficiency, and electrometer accuracy. Unit: C or rdg.

Value of the g (acceleration on the surface)

g=9.78 m/s^2

Huda: 99m-Tc production mode and decay mode

generator (99-Mo), isomeric transition to 99-Tc ground state

Bethe formula def: mean excitation potential (I)

geometric mean value of all ionization and excitation potentials of an atom of the absorbing material

What's brain metabolism substrate

glucose

Podgorsak: which particles transmit the strong force

gluons

Podgorsak: which particles transmit gravitational force

gravitons (hypothetical)

energy classification of radiation generators

grentz-ray therapy, contact therapy, superficial therapy, orthovoltage (or deep) therapy, supervoltage therapy, megavoltage therapy

Anat: which type of brain tissue comprises the cerebral cortex

grey matter (neutrons an their unmyelinated fibers). Underneath is white matter (myelinated axons) interconnecting different regions of the CNS

Huda: most likely radiation induced abnormality occuring at 70 to 150 days after conception

growth and mental retardation

Planck's constant in eV*s

h = 4.14 x 10^-15 eV*s

Huda (ultrasound): what is the lower limit for axial resolution in US

half pulse length, so the value in mm depends on frequency

Def: secular equilibrium

half-life of the parent is much longer than the half-life of the daughter

What does hematocrit measure

hematocrit or packed cell volume (PCV) is the proportion of blood volume that is occupied by red blood cells

Def: Nyquist frequency

highest spatial frequency that can be faithfully reproduced

Barium used in barium scan is used to

highlight uptake in abdominal CT

Compton formula for energy of secondary photon hv'

hv' = hv/(1+hv/m0c2(1-cos(scattering angle)))

Energy of 90 deg scattered photon for high incident photon energies

hv' = hv/(1+hv/m0c2) =~ 511 keV (because hv/m0c2 is >>1, so the additional 1 can be neglected)

Compton max backscattered photon energy

hv'=hv/(1+hv/m0c2(1-cos(180)))=~511/2 keV

Which free radical species produces the majority of damage to DNA

hydroxyl radical (OH*)

Huda (ultrasound): what is the critical angle in refraction of US

if velocity in medium 2 > velocity in medium 1, then sin(critical angle) = sin(incidence angle)/sin(90) = V1/V2

TG 75 title

imaging dose during image-guided radiotherapy

where is peritoneum located

in abdominal cavity

Anat: where is CSF produced

in choroid plexus

Podgorsak def: CEMA

in electron beams: energy lost by beam particles only (not secondary electrons) in material. If delta ray equilibrium exists, CEMA=DOSE

Where are the vocal cords located

in larynx

Huda: most likely radiation induced abnormality occuring after 150 after conception

increased risk of childhood malignancies

KHAN: BSF dependence on field size

increases with increasing field size

Khan: dmax for electrons decreases or increases with field size

increases with increasing field size (until lateral equilibrium is reached)

mass Compton effect interaction coefficient dependence on atomic number and incident photon energy

independent of Z (electron density only matters, which is almost constant except for materials with lots of hydrogen), decreases with energy

Huda (ultrasound): dependence of acoustic impedance of frequency in diagnostic region

independent of frequency

What do the islets of Langerhans produce

insulin

Huda (ultrasound): what are harmonic frequencies

integral multiplies of the fundamental frequency

Relation between intensity of x-ray production and x-ray tube potential

intensity is proportional to square of the potential

Khan: definition of the "virtual source" for electrons

intersecion point of the backprojections along the most probable directions of electron motion at the patient surface

How to find practical (or extrapolated) range in electron dosimetry

intersection of a tangential line crossing through R50 with the depth axis

Huda (MRI): how do contrast angents in MRI work

introduce local magnetic field inhomogeneity which affect T1 and/or T2

TG-21: name and unit of Nx

ion chamber exposure calibration factor (Roentgen/Coulomb)

Huda: name of the nuclides having the same mass number

isobars

Huda: describe 99mTc decay modes

isomeric transition producing 140 keV gammas in 90% of decays, in 10% internal conversion emitting characteristic x-rays and Auger electrons

Huda: name of the nuclides having the same number of neutrons

isotones

which kind of microwave generator in a linac is preferred and why

it is the klyston because it outputs more microwave power. Magnetrons are simpler, create less microwave power, and last shorter.

TG-51 def: formula for quality conversion factor in electron beams

kQ = PQgrkR50=PQgrk'R50kecal

describe the design and function of the klystron

klystron is a microwave amplifier. Consists of an electron source, buncher cavity, drift cavity, and catcher cavity. Low power microwaves modulate the electron current (create bunches) which in turn create charges on the ends of the cavity thereby generating retarding electric field for the electrons, that emit microwaves.

orbital angular-momentum quantum number allowed values

l = 0,1,2 .., n-1

dry eyes may result from radiation damage of ...

lacrimal glands

Formula for wavelength of X-ray given energy in keV

lambda (Angstroem) = 12.4/E(keV)

Formula for de Broglie wave of a mass (m) moving at velocity (v)

lambda = (Planck's constant)/(mass * velocity)

KHAN def: physical penumbra

lateral distance between two specified isodose curves at a specified depth (e.g. 90% and 20% at Dmax)

What part of the eye is the most radiosensitive

lens

Podgorsak: linear and mass attenuation coefficient for pair production variation with energy

linear proportional to ~Z^2, mass proportional to ~Z

Huda (MRI): what is functional MRI

local blood flow and blood oxygenation changes are associated with a certain brain site

Huda (MRI): in small molecules such as water and in large molecules such as proteins, the T1 is short or long

long

Huda (MRI): liquids have usually short or long T2 times

long

Huda (MRI): what combination of TE and TR (long or short) should be used to obtain T2-weighted image

long TR and long TE

Huda (MRI): what combination of TE and TR (long or short) should be used to obtain proton density image

long TR and short TE

LI: disadvantage of radiochromic film

low sensitivity

Symptom of 1 Sv acute total body irradiation

lower lymphocyte count

Lymphoma arisies from what type of tissue

lymphocytes of the immune system

Huda: most radiosensitive types of blood cells

lymphocytes, subtype of leukocytes (white blood cells)

this cancer type has the shortest latency period

lymphoma

Podgorsak: Einstein's relation between relativistic and rest mass

m(v) = m<sub>o</sub>/sqrt(1-(v/c)^2)

Huda (radition protection): workload unit for a radiation device

mA-minute/week

describe the design and function of the magnetron

magnetron produces microwaves. it is a cylinder with a central cathode and outer anode with resonant cavities. Constant magnetic field is applied in the transverse plane and DC pulses between anode and cathode. Complex motion of electrons toward resonant cavities creates microwaves.

Huda def: limiting spatial resolution

maximum number of line pairs per millimeter that can be recorded by the imaging system

Huda def: film gamma

maximum slope of the linear portion of the characteristic curve

Huda: increase of childhood leukemia risk per 10 mGy in the second or third trimester

may be as high as 40% (leukemia risk in general is very low)

Huda def: film gradient

mean slope between two specified film optical densities

Huda (ultrasound) def: beam intensity

measure of the energy associated with the beam, proportional to the square of amplitude

LI: principle of calorimetry

measure temperature increase with absorbed dose. Temperature sensitivity of water: 2.39x10-4 C/Gy

a primary tumor of the coverings of the brain

meningioma

magnetic quantum number allowed states

ml = -l to l (where is orbital angular-momentum quantum number)

What is buccal cavity

mouth, oral cavity

spint quantum number allowed values

ms = +1/2 or -1/2

formula for energy absorption coefficient muen

muen=(energy transfer coeff)x(1-(fraction of secondary particle energy lost to bremsstrahlung))

Formula for energy transfer coefficient (mutr)

mutr=(average energy transferred into kinetic energy of charged particles)/(incident photon energy)x(interaction coefficient)

Huda (ultrasound): what is the Fresnel zone

near field of US beam

Particles emitted in electron capture

neutrino (+characteristic X-ray or Auger electron)

TG-43 (brachy): in contrast to older method, what input data are required for the dose calculation

no exposure rate constant (point source) with tissue attenuation factor but dose rates from the actual source in a tissue equivalent phantom

TG-51 def: MU

number of monitor units (or minutes for 60Co) for which a given irradiation is performed

Huda def: film contrast

observed optical density difference measured on a film for a given exposure difference incident on a film

Anat: where are adrenal glands located

on top of each kidney

Anat: describe visual pathway from the eye to the brain

optic nerve from photoreceptive cells on retina to lateral geniculate nucleus (in thalamus) to primary and secondary visual cortex (rear of the brain, above cerebellum). Crossing of the optical nerves: optic chiasm

what does the magnetic quantum number (m) describe

orientation of the electron's magnetic moment in an external magnetic field

Huda (MRI): what is free induction decay signal

oscillating signal induced by the oscillating longitudinal magnetization vector following a 90 deg RF pulse

function of the GTV

outlines the visible of demonstrated tumor volume

Anat: where is foramen magnum

oval opening in the bease of the skull (through which medulla oblongata enters)

Formula for photon momentum

p = (Planck's constant)/(wavelength) = (Energy)/(speed of light)

Podgorsak: how different is pair from triplet production

pair production occurs in electrostatic field of the nucleus, triplet production in the electrostatic field of an orbital electron

Anat: which organ produces insulin

pancreas

dry mouth may result from radiation damaga of which gland

parotid

Anat: what is hiatal hernia

part of the stomach pushes up through diaphragm through the esophagus opening

By what physical transport mechanism does oxygen move into the bloodstream

passive diffusion (iron has great affinity for oxygen)

KHAN: formula for the value of pdd(depth,SSD,field size) using TAR and BSF

pdd(depth,SSD, field size) = TAR(depth, field size at depth)/BSF(field size at dmax)(SSD+dmax)2/(SSD+d)2 x 100

KHAN: formula for conversion of pdds with different field sizes using the TAR method

pdd(depth,field size on surface,SSD1)/pdd(depth,field size on surface,SSD2) = TAR(depth,field size 1 at depth)/TAR(depth, field size 2 at depth) x (Mayneord factor)

TG-51 def: kecal

photon-electron conversion factor. Needed to convert N60CoD,w into an electron beam absorbed-dose calibration factor NQecalD,w for a selected beam quality Qecal. Note that: kR50=k'R50kecal

Podgorsak: which particles transmit the electromagnetic force

photons

pair production coefficient (pi) per atom dependence on Z and E

pi ~ Z2 and log(E)

What is the "master gland"

pineal gland

the gland that controls sleeping and waking through secretion of melatonin

pineal gland

TG-51 def: Ppol

polarity correction factor which takes into account any polarity effect in the response of the ion chamber

Which blood vessel provides the liver it's nutrients from small intestine

portal vein

Huda (MRI): what is Larmor frequency

precession frequency of nuclei in a magnetic field

Def: average glandular dose in mammography

preferred measure of dose, determined using a special phantom

Huda (radiation protection): what does the primary barrier do

primary barrier absorbs primary radiation

Def: dose-area product in imaging

product of entrance skin dose and cross-sectional area of the x-ray beam (exposed area)

What does the sensitivity of the study represent

proportion of actual positives which are correctly identified

Podgorsak: atomic cross-section for Rayleigh scattering variation with Z and E

proportional to (Z/E)^2

Hendee: Pair production dependence on energy and material atomic number

proportional to E and Z

Podgorsak: mass attenuation coefficient for Rayleigh variation with Z and E

proportional to Z/E^2

Hendee: Dependence of bremstrahlung production on atomic number

proportional to Z^2

Podgorsak: mass scattering power for electrons variation with atomic number and electron kinetic energy

proportional to Z^2/E^2

Podgorsak: atomic interaction coefficient for photoelectric effect variation with Z and E

proportional to Z^4/E^3

Huda: estimated proportionality of patient exposure from an X-ray tube with current and voltage

proportional to tube current and (tube voltage)^2

Gleason score is used for staging of what type of cancer

prostate

Anat: where is the pituitary gland

protrosion off the bottom of hypothalamus at the base of the brain, in pituitary fossa

function of the PTV

provides margin around the target to account for errors in setup, laser alignment, etc.

function of the CTV

provides margin around the visible tumor volume to account for microscopic extension of the tumor

Huda (ultrasound): what determines axial resolution in US

pulse length

def: quality of the photon radiation field

quality is the penetrating ability

Huda def: speed of a screen/film combination

quantity inversely related to the exposure required to produce a given intensity

Huda: most likely radiation induced abnormality occuring at 50 to 70 days after conception

radiation induced microcephaly (head considerably smaller than normal)

Huda def: X-ray tube leakage radiation

radiation that is transmitted through the x-ray tube housing

LI: which film is tissue equivalent, does not require developing, and has very small energy dependence

radiochromic film

TG-51 def: rcav

radius of the air cavity in a cylindrical ion chamber. Unit, cm.

Def: quantum mottle of an image

random variation of number of photons incident on a radiation detector

Huda def: film latitude

range of exposure levels over which the film may be used

Huda (MRI): in image MRI formation: how is a slice selected

range of resonant frequencies of the RF pulse matches a given range of z positions. the range of frequencies of the RF pulse defines slice thickness

Huda def: film dynamic range

ratio of highest to lowest exposure that can be usefully detected

KHAN def: primary off-axis ratio at depth d (OARd(x))

ratio of primary dose at the off-axis point of interest to the primary dose at the central axis at the same depth for a symmetrically wide open field

KHAN def: TPR

ratio of the dose at a given point in phantom to the dose at the reference depth in phantom (usually 5 cm) and the same distance from the source

KHAN def: TMR

ratio of the dose at a given point in phantom to the dose at the reference point of maximum dose (t0, independent of SSD and field size) and the same distance from the source

Khan: wedge (transmission) factor

ratio of the dose at a specified depth along the main axis (e.g. at 10 cm depth) to the dose without the wedge

KHAN def: phantom scatter factor (Sp)

ratio of the dose rate for a given field at a reference depth (e.g. dmax) to the dose rate at the same depth for the reference field size, with the same collimator opening

def: coefficient of internal conversion

ratio of the number of emitted electrons to the number of emitted gamma rays

KHAN def: collimator scatter factor (Sc) or output factor

ratio of the output in air for a given field size to that for a reference field size

KHAN def: SMR

ratio of the scattered dose at a given point in phantom to the effective primary dose at the reference depth of maximum dose and the same distance from the source

KHAN def: SAR

ratio of the scattered dose at a given point in the phantom to the dose in free space at the same point

Fluoroscopy: purpose and main components

real-time observation of dynamic activities (e.g. contrast moving through structures). Consist of x-ray tube, image intensifier, optical system, tv camera

Anat: function of cerebellum

receives information from sensory systems, cord and other parts of brain and regulates voluntary motor movements

Huda (ultrasound) def: specular reflection

reflection from a large smoot surface (major contributor to US image)

LI: principle of chemical dosimetry

relate production of Fe3+ from Fe2+ ions to dose. measure Fe3+ concentration (G-value). Fe3+ has absorption peaks at 224nm & 304 nm.

what is the characteristic curve of the film

relation between log relative exposure (x) and optical density (y)

Huda: Computed Tomography images are maps of ...

relative linear attenuation values of tissues

Huda: difference between relative risk model and absolute risk model for cancer induction

relative risk model: radiation increases the natural incidence of cancer by constant fraction; absolute risk model: (...) increases by a given number

TG-21 def: Prepl

replacement factor that corrects for perturbation in the electron and photon fluences at point P (center of the cavity) as a result of insertion of the cavity in the medium

What does the "transurethral resection" refer to

resection of prostate

Where does the blood from the pulmonary artery come from

ritght ventricle

TG-51 def: %dd(10)Pb

same as %dd(10) except that a 1 mm lead foil is in place below the accelerator at about 50 cm from the phantom surface ( 30 cm if 50 cm clearance is not available)

name of the cancer arising in connective tissue cells such as bone cartilage and fat

sarcoma

Huda (ultrasound) US attenuation is a composite effect of 2 phenomena

scatter and absorption

Huda (radiation protection): what does the secondary barrier do

secondary barrier protects workers from scattered radiation

Anat: what does the pituitary gland do

secretes hormones regulating homeostasis that stimulate other endocrine glands

loss of balance might result from the damage of ...

semicircular canals

Huda (MRI): in fats and intermediate size molecules the T1 is short or long

short

Huda (MRI): large molecules and solids have usually short or long T2 times

short

Huda (MRI): what combination of TE and TR (long or short) should be used to obtain T1-weighted image

short TR and short TE

KHAN: formula for the side length of a square field that is equivalent of a rectangular field

side length = 4 (area)/(perimeter)

Huda (ultrasound): Snell's law

sin(theta_incident)/sin(theta_transmitted) = (velocity in incident region)/(velocity in transmitted region)

Huda: how do 4th generation CT scanners work

single tube wide fan beam), stationary detectors all around gantry, only tube rotates

Huda: how do 1st generation CT scanners work

single tube-detector (narrow parallel beam) translates across patient, then increment the angle and repeat

Huda (MRI): what is chemical shift in MR imaging

slight change in resonance frequency of protons due to molecular structure

Imaging: the modulation transfer function relaties which image properties

spatial resolution and contrast

MRI def: T1

spin-lattice (longitudinal) magnetization recovery time constant

MRI def: T2

spin-spin (transverse) magnetization decay time constant

Anat: which organ removes red blood cells

spleen

Duct narrowing is called...

stenosis

Huda: radiation protection is designed to minimize deterministic or stochastic effects?

stochastic

Huda def: pincushion distortion in image intensifiers

straight lines appear curved

Podgorsak: quarks exhibit strong or weak interactions

strong

Hendee def: Collective Dose Equivalent

sum of the dose equivalents for individuals in a population, unit [person-sievert]

Huda def: X-ray tube stray radiation

sum of the leakage and scatter radiation

formula for value of the Student t-test

t = abs(average1-average2)/sqrt(sigma1^2+sigma2^2)

Huda def: helical (spiral) computed tomography pitch

table movement during each revolution of the x-ray tube divided by the collimation width

mass photoelectric effect coefficient (tao/rho) dependence on atomic number and photon energy

tao/rho ~ Z3/E3

TG-51 def: T (temperature)

temperature of the air inside an ion chamber, taken as the temperature of the surrounding water when in thermal equilibrium

typical radiographic exposure time

tens to hundreds of millisecond

TG-51 def: DQw

the absorbed dose to water for a given number of monitor units ~or minutes for 60Co) from a radiation beam of quality Q. Unit: gray, Gy.

TG-51 def: ND,w

the absorbed-dose to water calibration factor for an ion chamber located under reference conditions in a radiation beam. The absorbed dose measured is that at the chamber's point of measurement in the absence of the chamber. For a vented ion chamber the calibration factors from US and Canadian calibration laboratories apply for standard environmental conditions of temperature, pressure, and relative humidity. Calibration factors apply assuming the chamber reading corresponds to 100% charge collection efficiency. In contrast, calibration factors are usually for a stated polarity and corrections are needed if there is a significant polarity effect in the calibration beam. Unit: Gy/C or Gy/rdg.

Def: wedge (isodose) angle

the angle (between the isodose and the normal to the central axis) through which an isodose curve is tilted at the central ray of a beam at a specified depth

TG-51 def: dmax

the depth at which the absorbed dose to water (not ionization) is a maximum for a given beam. In photon beams it may include effects of electron contamination in the incident beam. Unit: cm.

TG-51 def: reference depth

the depth at which the point of measurement of the ion chamber is placed to measure the absorbed dose

TG-51 def: I50

the depth in an electron beam at which the gradient-corrected ionization curve falls to 50% of its maximum. Unit: cm.

TG-51 def: R50

the depth in water in a 10x10 cm2 or larger beam of electrons at an SSD of 100 cm at which the absorbed dose falls to 50% of the dose maximum. For beams with R50>8.5 cm (energy greater than roughly 20 MeV), a 20x20 cm2 or greater field size is needed. Unit: cm.

TG-51 def: Pelec

the electrometer correction factor. If the electrometer is calibrated separately from the ion chamber, then Pelec is the electrometer calibration factor which corrects the electrometer reading to true coulombs. Pelec is considered 1.00 if the electrometer and ion chamber are calibrated as a unit. Unit: C/rdg or C/C.

TG-51 def: k'R50

the electron quality conversion factor. Needed to convert NQecalD,w into NQD,w for any beam quality Q. Is a function of the electron beam quality specified by R50. Note that kR50=k'R50kecal

what does the orbital-momentum quantum number (l) describe

the electron's angular momentum

TG-51 def: PQgr

the gradient correction factor is the component of kQ in an electron beam that is dependent on the ionization gradient at the point of measurement for cylindrical chambers only. PQgr is a function of the radius of the cavity, rcav and the local gradient. PQgr is unity for plane-parallel chambers. The equivalent factor in photon beams is accounted for within kQ since it is the same for all beams of a given energy

What is the shoulder of the survival fraction curve

the initial dose region in which there is less cell inactivation per unit dose

def: effective dose

the mean absorbed dose from a uniform whole-body irradiation that results in the same total radiation detriment as from the non-uniform, partial-body irradiation in question

TG-51 def: %dd(10)

the measured photon beam percentage depth dose at 10 cm depth in a 10x10 cm2 field on the surface of a water phantom at an SSD of 100 cm (includes electron contamination).

Conceptually: what determines the dmax depth for photons in a medium

the most probable range of the charged particles

Podgorsak def: fluorescent yield

the number of characteristic X-rays emitted per orbital electron shell vacancy

TG-51 def: %dd(10)x

the photon component of the photon beam percentage depth-dose at 10 cm depth in a 10x10 cm2 field on the surface of a water phantom at an SSD of 100 cm

TG-51 def: point of measurement

the point at which the absorbed dose is measured. For cylindrical ion chambers used for clinical reference dosimetry the point of measurement is on the central axis of the cavity at the center of the active volume of the cavity and for plane-parallel chambers the point of measurement is at the upstream side of the air cavity at the center of the collecting region

TG-51 def: kQ

the quality conversion factor, which accounts for the change in the absorbed-dose to water calibration factor between the beam quality of interest, Q, and the beam quality for which the absorbed-dose alibration factor applies (usually 60Co). kQ is a function of the beam quality Q [specified by %dd(10)x or R50] and is chamber dependent. For 60Co beams kQ=1.000 by definition.

TG-51 def: Pion

the recombination correction factor takes into account the incomplete collection of charge from an ion chamber. Unlike the TG-21 protocol, this factor does not appear explicitly in the dose equation but it is now taken into account when determining the corrected charge reading M.

KHAN: how to determine reference depth of maximum dose (t0)

the reference depth cannot be on the buildup region, so the reference depth has to be deeper than the maximum dmax (i.e. maximum SSD and 0 field size).

TG-51 def: PTP

the temperature-pressure correction factor which makes the charge or measured current correspond to the standard environmental conditions for which the calibration factor applies

Radioactivity: how can be "average life" defined

the time a sample would take to complete decay at the initial disintegration rate

TG-51 def: NQD,w

the value of ND,w in a photon or electron beam of quality specified by Q

Huda formula: mass thickness

thickness * density

Def: half value layer

thickness of material that attenuates an x-ray beam exposure by 50%

Huda (ultrasound): what information is presented in M mode

time (X axis) intensity (pixel brightness) depth (Y axis), shows time-dependent motion of an interface

The major function of small intestine is

to absorb nutrients

Huda (ultrasound): why is gel used in US imaging

to displace air. air-tissue interface reflects almost entire US beam

why should the wall material of the thimble chamber be equivalent to air

to ensure that the electron spectrum produced is the same as in air

Where does the vena cava dump

to right artrium

what is the function of the gall bladder

to store bile

Def: integral dose

total amount of energy (in mJ) imparted to a patient

Radioactivity: what is radium A

traditional name for 218-Po

How is specificity of a test defined on a 2x2 decision matrix

true negatives / (true negatives + false positives)

How is sensitivity of a test defined on a 2x2 decision matrix

true positives / (true positives + false negatives)

Def: heel effect in X-ray tube

tube anode target angle is 6-17 degrees; when X-rays are produced deeper in the target, the outgoing intensity decreases from the cathod to the anode direction of the beam

Huda (radiation protection): def: radioactive contamination

uncontained radioactive material where it is not wanted

TG-51 def: Mraw(d)

uncorrected ion chamber reading with the point of measurement of the ion chamber at a depth d in water, for a given number of monitor units (or minutes for 60Co). If no sign is indicated, the measurement is made collecting the same charge as during calibration. If a sign is indicated (+ or -), it is the sign of the charge collected. Unit: C or rdg (meter reading).

KHAN: maximum photon kVp for which the reference depth is at the surface

up to 400 kVp (orthovoltage)

Most often location of the breast cancer

upper outer quadrant

TG-51: technique for measuring Pion

use 2 different bias voltages: nominal and at least a factor of 2 lower. wait a few minutes after changing the voltage.

TG-75: conversion of absorbed dose to effective dose in imaging

use a semiempirical conversion factor F in units of mSv per mGy

TG-51: methods of clinical reference dosimetry at depths other than 10 cm for SSD setups

use clinical depth-dose curves

medical accelerator types

van de graaff, linac, betatron, microtron, cyclotron, synchrotron

Huda (MRI): what is magnetic moment of a nucleus

vector that represents the strength and orientation of a magnetic dipole

Anat: Where is the vision processing center of the brain located

visual cortex is located in the occipital lobes

def: sensitivity of an ionization chamber

voltage drop per roentgen

TG-51 chamber primary calibration medium and photon energy

water and 60Co

Anat: how are joints lubricated

with synovial fluid

Beam active Linac head components order in photon mode

x-ray target, primary collimator, flattening filter on carousel, ion chamber, secondary collimator

Ultrasound: formula for ideal impedance of the coupling medium

z_ideal_coupling = sqrt(z_transducer * z_medium)

Huda (MRI): what is magnetic moment of a nucleus with the same amount of protons and neutrons

zero (protons and neutrons pair up their magnetic moments in opposite directions, cancelling each other out)

Formula for the total length of a vector C that is a sum of vectors A and B

|C| = sqrt(|A|^2 + |B|^2 - 2*|A|*|B|*cos(alpha))

Huda: percentage of cosmic rays that reach sea level

~0.05%

Design of radiographic film

~10 um emulsion containing silver halide (iodobromide) grains supported by 150-200 um Mylar base

Huda: approx. energy threshold for photodisintegration

~15 MeV

maximum photon energy beyond which the exposure is not defined

~3 MeV


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