Radiation oncology physics ABR
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
