RAD BIO review 1 Flashcards
what are some of the ways we can measure radiation?
primary radiation
secondary radiation (as leakage radiation)
patient absorption
healthcare absorption
what are the common radiation measurements?
exposure (air)
air kerma (air)
absorbed dose (tissue)
equivalent dose (tissue)
effective dose (tissue)
What are the measurements of air?
what are some of the measurements of tissue?
exposure & air kerma (air)
absorbed dose, equivalent dose, & effective dose
the intensity of the x-ray beam is measured by?
what does this measure?
exposure or air kerma
amount of radiation exiting the x-ray tube directed at patient
what measures the leakage radiation escaping the tube housing?
exposure & air kerma
what is the order of measurement for patient/occupational dose?
absorbed dose
converted to equivalent dose
converted to effective dose
what does absorbed dose tell us?
what does it not?
absorbed energy & short-term effects (skin erythema or hair loss)
long-term effects (cancer)
if we increase the kVp or mAs and don’t change anything else what happens to intensity, exposure, air kerma, absorbed, equivalent, & effective dose?
what if we increased distance?
intensity increases
exposure & air kerma increase
absorbed, equivalent, & effective dose increase
all of these decrease
(all of these factors are directly related)
what does effective dose tell us?
what does it not?
what is it the opposite of?
long-term effects
absorbed energy & short-term effects (best for measuring cancer)
absorbed dose
(t/f) All radiation measurements in diagnostic imaging fall into two categories
what are they?
true
radiation in air & radiation in tissue
radiation that escapes the protective housing of the x-ray tube is known as?
leakage
which of the following radiation measurements are used to quantify the risk of the long-term radiation injuries, such as cancer?
effective dose
Exposure and air Kerma are important for?
occupational & patient safety
exposure measures?
the number of ionizations in the air
increase in beam intensity, ______ ionizations & _________
increases
exposure
what are the units of measurement for exposure?
coulombs/kilograms (per kg)
one coulomb is equal to?
1C= 6.242x10^18 ionizations
how are we able to measure exposure in micro-coulombs?
increase MA/KVP increases photons, ionizations, & exposure
Air Kerma measures?
the energy of ionizations in the air
how does Air Kerma & exposure differ?
Exposure measures the number of ionizations
air Kerma measures the energy of ionizations
what does KERMA stand for?
kinetic
energy
released per unit
MAss
the primary by-product of x-ray interactions in air is?
free electrons
KERMA is measured by?
gray (=1 joule per kg)
what are the measurements for AIR KERMA & GRAY?
joules (energy) per kg (mass) (gray)
coulombs per kg
what is the process through which x-rays create charged particles such as free electrons?
ionization
exposure is a radiation measurement used to quantify which of the following?
absolute number of ionization events in air
Air KERMA is a radiation measurement that describes the:
kinetic energy absorbed by ions in air
what units are used to measure exposure?
coulombs per kg (C/kg)
Air Kerma & exposure:
only measure radiation and error directed towards the patient/occupational
what best describes radiation exposure?
quantity of radiation directed at the patient
what does absorbed dose tell us?
how much radiation is absorbed in patient/occupational
absorbed dose comes from?
photoelectric absorption & Compton scattering
what is absorbed dose?
energy absorbed in the body (per unit mass)
absorbed dose calculation:
1 gray= 1 Joule per kg
(J/kg)
(ex 0.009J/ 1.5kg=0.006 Gy)
what negative effects can be caused by absorbed dose?
sperm depression (100 mGY)
skin erythema (2,000 mGy)
epilation (3,000 mGy)
what other variables affect the absorbed dose?
tissue thickness
tissue density
tissue with high atomic number
units of measurement for absorbed dose is?
Gy or mGy
absorbed dose is commonly used to describe which of the following?
quantity of radiation absorbed in the patient
How is absorbed dose calculated?
how is exposure measure?
how is Air Kerma measured?
(J/kg)
(C/kg)
(J/kg)
what dose LET stand for?
what is it?
linear energy transfer
the rate at which radiation energy is deposited in matter
what is the equivalent dose (EqD) formula?
D x Wr
dose x radiation weighting factor
x-rays have a _____ LET
alpha particles have a ____ LET
low
high (concentrated)
higher LET =
more biological harm
what are these?
LET?
RBE?
WR?
EqD?
linear energy transfer
relative biological effectiveness
radiation weighting factor
equivalent dose
what is the main reason for equivalent dose?
compare biological damage from different radiation types
equivalent dose is affected by?
radiation type (Wr)
absorbed dose (D)
kVp/ mAs
exposure time
distance
what is the effective dose calculation (EfD)?
D x Wr x Wt
( absorbed dose x radiation weighting factor x tissue weighting factor)
what variable must be known to calculate the effective dose (EfD)?
absorbed dose
exposed tissue types
radiation type
equipment survey devices ensure proper?
radiation output of x-ray machines
who use the equipment survey devices?
medical physists
Survey devices also ensure that mA and kVp assigned are:
the actual kVp & mAs output during exposure
what do environmental survey devices monitor?
they are for?
what is an example of one?
radioactive contamination & x-ray transmission
occupational & public safety
Geiger counter (GM counter)
personal dosimetry device track radiation dose to:
occupational workers
how do we measure radiation?
interacts with detector of the device
convert anergy into a unit of measure (mGy)
radiation equipment survey devices evaluate?
environmental radiation survey instruments evaluate?
personal dosimetry devices evaluate?
radiation output of x-ray machine
radioactive contamination
occupational radiation dose
what type of radiation detection instrument is used to check MA and KVP?
what type of radiation detection instrument is used to detect dose to radiographer?
equipment survey device
personal dosimetry device
who is qualified to operate equipment survey devices?
medical physicists
in order to be measured, radiation must interact with the:
detector
what is an ionization chamber?
metal chamber filled with air or gas
what is an ionization chamber that serves as an occupational dosimeter?
pocket ionization chamber
the radiation-sensitive portion of an ionization chamber is composed of:
A radiation measurement is acquired by ionization chamber when radiation:
air
ionizes the air in the chamber
an ionization chamber calibrated to measure air kerma will display units of:
exposure?
equivalent dose?
Gray (Gy)
C/kg (coulombs per kg)
sieverts per hour (Sv/hr)
scintillation devices are effective for measuring ________ surveys
who uses these?
environmental
nuc med techs & medical physicists
scintillation device is comprised of ___ parts
what are these?
3
scintillation crystal (absorbs alot of radiation)
photocathode (create electrons, light to electrons)
photomultiplier tube (multiply’s the weak photocathode signal)
Scintillation is a process that creates?
visible light
what is measured during the process of gamma spectroscopy?
photon energies (keV)
what is the radiation-sensitive portion of scintillation detector composed of?
light-emissive crystal
the function of scintillation crystal is to convert?
photocathode layer?
photomultiplier?
x-rays into light
light into electrons
electrons into more electrons
what are types of semiconductor dectectors?
hand-held detector
x-ray testing detector
AEC cells
DR receptor
units for semiconductor detectors:
are used to evaluate ____ energy
radioactivity, bequerel, CPM (counts per min), CPS (counts per sec)
photon (keV or mEv)
one difference between scintillation detectors and semicondictors?
semiconductors do not produce visible light
what is the function of the semiconductor crystal?
convert x-rays into electrons
the radiation-sensitive portion of a semiconductor detector is composed of?
electron-emissive crystal
what is the annual effective dose limit to the whole body? purpose?
limit to the eyes? purpose?
skin/extremity? purpose?
50 mSv & to limit stochastic effects like cancer
150 mSv & prevent radiation induced cataracts
500 mSv & limit deterministic effects
for members of the public the dose limits are all _____ of the occupational dose limit
what are these for whole body, eyes, & skin?
10%
5 mSv, 15 mSv, 50 mSv
What are TLD & OSL?
do they have the same fnction?
thermoluminescent dosimeter & optically stimulable luminescent
yes
what are the type of radiation detector devices?
film badge
pocket ionization
TLD (most common)
OSL (most common)
OSL & TLD track ___ over time
this is read ____ and tracks the ___ ___ ___ limits
dose
quarterly
skin, lens, & whole body
_______ ______ _______ absorb all forms of ionizing radiation in TLD
lithium fluoride crystal
the loss of stored radiation dose energy is called:
fading
disadvantages of TLD?
fades in high heat or light
can only be read once
OSL is comprised of:
aluminum oxide crystal
what is an advantage of OSL?
disadvantage?
more sensitive to radiation, can be read multiple times, & not fade in heat or light
more expensive than TLDs
