I. Radiation Physics and Detection (7%)
annihilation of an electron and a positron results in a pair of ___ gamma rays traveling ___ degrees.
0.511MeV; 180°
the decay factor for Tc-99m at 2 hours is: ___.
0.794
what is the minimum angle at which a photon can scatter in the Compton effect?
0°
the radiation intensity from a point source of Tc-99m is 9mR/hr at 3m from the source. if the distance is changed to 9m, what is the new radiation intensity?
1.0mR/hr
how many known processes are there by which gamma rays interact with matter?
12
a source of F-18 (t1/2 approximately 2 hours) is noted to contain 3mCi at noon. what is the radioactivity at 8am the same day?
12mCi
photon energy of Tc-99m is ___.
140keV
a dose of Tc-99m has an activity of 26.3 mCi at 10:30. What is it's activity at 14:10?
17.2mCi
1 Hz = ___.
1cps
a radiologist orders an In-111 cerebrospinal fluid shunt study. the dose vial comes with a label indicating: activity 1.5mCi, volume 1ml. the ordering physician specifies an injection of 0.5mCi in a 0.5ml volume. the technologist will first need to withdraw 0.33ml (which will contain the prescribed 0.5mCi) from the dose vial, and then dilute it with saline to have the prescribed volume of 0.5ml. what will the final concentration in the dose to be injected?
1mCi/ml
alpha particles are made up of:
2 protons and 2 neutrons
10mCi is equal to how many becquerels?
370MBq
what is the minimum energy threshold required for pair production to occur?
511keV
the dose equivalent for occupational, whole-body exposure is commonly limited to 50mSv. how many rem is this?
5rem
an attenuator that is equivalent to 4 half value layers would reduce the radiation to ______ of its original strength.
6.25%
half-life of Tc-99m = ___.
6hr
a dose of F-18 FDG is 15 mCi at 8:45. What is it's activity at 10:20?
8.2mCi
all nuclides with an atomic number greater than ___ are radioactive.
82
mass number
A
neutron number
N
the annihilation priniciple is upon which ___ is based.
PET
atomic number
Z
gamma photons are:
a weakly ionizing, highly penetrating type of radiation
what is the primary characteristic of bremsstrahlung radiation? a) it consists of high-energy photons b) it is emitted by positrons c) it is only produced in nuclear reactors d) it is not affected by electric fields
a) it consists of high-energy photons
in which of the following processes is bremsstrahlung radiation commonly observed? a) medical x-ray imaging b) nuclear fusion reactions c) beta decay d) neutrino interactions
a) medical x-ray imaging
in order for momentum to be conserved, another ___ must be present, so gamma photons cannot interact with free electrons via photoelectric effect.
all of the above
the most important gamma interaction is:
all of the above
what is an auger electron?
an electron that is ejected from an outer orbital of an atom due to excess energy.
what happens after a photoelectron is ejected from an atom during the photoelectric effect?
another electron from an outer shell fills the vacancy.
ionization is defined as:
any process that results in the removal of an electron from an atom or molecule thereby leaving the atom or molecule with more protons
how is the excess energy, after the photoelectron is ejected, typically emitted from the atom?
as characteristic x-rays or an auger electron
mass number is approximately equal to the ___ of the atom in ___.
atomic mass; amu
what is bremsstrahlung radiation? a) radiation emitted by radioactive materials b) radiation emitted by accelerated charged particles c) radiation emitted during nuclear decay d) radiation emitted by the sun
b) radiation emitted by accelerated charged particles
___ are faster than alpha particles, but slower than the speed of light.
beta particles
beta particle emitting radionuclides should not be shielded by a high-Z material (such as lead) because ___ interactions are likely to occur.
bremsstrahlung
how does pair production contribute to radiation therapy?
by producing the electrons for treatment
what is the primary mechanism behind the production of bremsstrahlung radiation? a) electron-positron annihilation b) atomic excitation c) acceleration of charged particles d) neutron decay
c) acceleration of charged particles
velocity is a ___.
constant
wavelength ___ as you go up the spectrum and frequency ___.
decreases; increases
which of the following best describes the process of the photoelectric effect?
electrons are ejected from a material when it is exposed to light or radiation.
in the Compton effect, what quantity is conserved?
energy
the amount of energy depends on the ___.
frequency
wavelength is inversely proportional to ___.
frequency
what are the characteristics of energy waves?
frequency, wavelength, velocity
what type of radiation is produced during the annihilation of an electron and a positron?
gamma
the common unit of frequency is:
hertz
which type of materials are more likely to exhibit the photoelectric effect with low-energy gamma rays?
high atomic number materials
in which type of material is pair production more likely to occur?
high-density materials
alpha particles are ___
highly ionizing, weakly penetrating type of radiation
the amount of bremsstrahlung ___ with the density of the material through which it passes.
increases
which of the following interactions is responsible for pair production?
interaction with a photon
nuclides with the same number of protons are called ___.
isotopes
what is the fate of the positron produced in pair production?
it annihilates with an electron, producing gamma rays
what happens when a photoelectron is ejected during the photoelectric effect?
it escapes the atom, leaving behind an ionized atom.
what happens to the wavelength of a photon after it undergoes Compton scattering?
it increases
what is the significance of the photoelectric effect in radiation protection?
it is a mechanism by which gamma rays can be absorbed and their energy deposited in a material.
what happens to the gamma ray in the photoelectric effect?
it is absorbed by an orbital election, causing it to be ejected from the atom
what happens to the excess energy in pair production?
it is converted into kinetic energy of the produced particles
how is annihilation radiation used in medical imaging?
it is used to create images of metabolic activity in the body
which of the following statements best describes the photoelectric effect?
it occurs when gamma rays of low energies interact with high atomic number materials.
in PET imaging, what role does annihilation play?
it produces gamma rays that are detected by the PET scanner
___ can block beta particles, but will cause bremsstrhlung radiation as a result because it is so dense.
lead
gamma radiation can be though of as waves of energy like ___.
light
the neutron number = ___.
mass number (A) - atomic number (Z)
isobars are nuclides with the same ___ but a different ___.
mass number; combo of protons and neutrons
beta particles are a ___ ionizing, ___ penetrating type of radiation.
moderately; moderately
the range of an alpha particle is ___ than other ionizing radiation.
much less
what is the total charge of the particles produced in pair production?
neutral
neutron number is the number of ___ in the nucleus.
neutrons
isotones are nuclides having the same number of ___ but different number of ___.
neutrons; protons
x-rays and gamma-rays have the same characteristics, but they are named based on their origin. x-rays are emitted from the electron shells, where gamma-rays are emitted from the ___.
nucleus
which of the following statements about pair production is true?
pair production can only occur in the presence of a nucleus.
what type of interaction occurs when a weak photon gives all of its energy to an inner shell electron?
photoelectric effect
what can shield beta particles without causing bremsstrahlung radiation?
plastic, water, wood, lucite
F-18 is an example of ___ decay process.
positron
atomic number is the number of ___ in the nucleus.
proton
positron decay or emission is when a _______________ is converted to a neutron, a positron, a neutrino, and energy.
proton
which of the following particles is not involved in the compton effect?
proton
mass number is the total number of ___ in the nucleus.
protons and neutrons (particles)
alpha particles are absorbed by a(n) ___.
sheet of paper
excitation is defined as:
the addition of energy to an atomic or molecular system, thereby exciting it from its ground state to a higher energy state.
which of the following best describes the change in energy of a photon undergoing compton scattering?
the change in energy is proportional to the initial energy of the photon.
what is pair production?
the creation of an electron-positron pair from a photon
wavelength is defined as:
the distance from a point on one wave to the same point on the next wave
how is the energy of the ejected electron related to the energy of the incident gamma ray in the photoelectric effect?
the energy of the ejected electron is equal to the energy of the incident gamma ray minus the binding energy of the electron.
how does the energy of a gamma photon affect an orbital electron in the photoelectric effect?
the energy of the gamma photon is imparted to the electron as kinetic energy, overcoming the attractive force of the nucleus and causing the electron to be ejected from its orbit with considerable velocity.
how does the energy of the incident photon affect the energy of the produced particles in pair production?
the energy of the produced particles is equal to the energy of the incident photon.
frequency is defined as:
the number of wave formations per unit of time
what is annihilation in the context of radiation?
the process of two particles colliding and destroying each other, producing energy
what is the compton effect?
the scattering of photons by electrons
velocity is defined as:
the speed at which the waves travel
bremsstrahlung is the same with positrons except:
there is repulsion instead of attraction
what happens when a positron collides with an electron?
they annihilate each other and produce gamma rays
how do gamma photons, which have no net electrical charge, interact with atoms to produce ionization?
they possess both an electric and magnetic field component, allowing them to interact electrically with atoms
what is the role of high z materials like lead in shielding against bremsstrahlung radiation?
they produce less secondary radiation
true or false: x-rays are not sheiled as easily as beta particles.
true
how are positrons used in medical imaging?
used in PET imaging
frequency is a ___.
variable
wavelength is as a ___.
variable
frequency is inversely proportional to ___.
wavelength
