arrt review: safety Flashcards
a ___ degree angle to the beam’s ________ and several feet away from the patient generally minimizes exposure
90, entry point
generally, a ______ kVp will result in a lower entrance skin exposure than a ______ kVp technique
higher, lower
what types of generators will yield lower entrance skin exposure?
three high/high frequency will be lower than single
two purposes of primary beam restriction
- restricts beam to area of interest
- reduces amount of tissue exposed to the radiation beam
types of beam restriction
collimators
positive beam limitation (PBL)
cylinders/cones
aperture diaphragm
formula for calculating field size
field size/aperature opening = SID/source to aperature opening distance
filtration that increases the effective energy and quality of the x-ray beam
hardening
maximum thickness requirements in useful beam
below 50 kVp
0.5 mm aluminum
maximum thickness requirements in useful beam
50-70 kVp
1.5 mm aluminum
maximum thickness requirements in useful beam
above 70 kVp
2.5 mm aluminum
total filtration = ______________ + ________________
inherent + added
what is included in inherent filtration?
the glass envelope, insulating oil, collimation mirrors
what is included in added filtration
aluminum (or other materials)
digital imaging eliminates retakes due to overexposure of up to __% and underexposure up to ___%
500%, 80%
air gap technique requires a __________ combined with _________
a long SID, an increased OID
air gap techniques do not ____________ but rather _____________
reduce scatter production, reduce its effect
why does an air gap technique work?
high percentage of scatter diverges away from the IR
1 inch = ___ centimeters
2.54 centimeters
minimum source to skin distance for fluoro units = ____ inches for fixed units, ___ inches for mobile
15 inches for fixed, 12 inches for mobile
what does DAP stand for?
dose area product
what is DAP used for?
used to measure total dose to patient site in order to reduce patient radiation dose
what is DAP expressed in?
mGy-cm2
minimum cord length on mobile x-ray unit
6 feet
DAP is the ________ striking the surface of the patient
total air kerma
medical imaging’s principle of radiation protection is based on the ____________________ dose response relationship
non-threshold, linear
1 mGy = __ mRm
100 mRm
natural sources of radiation; which is the largest?
radon, cosmic, terrestrial
radon is the largest
natural sources of radiation amount to __% of annual exposure to ionizing radiation
82%
how much average yearly dose from all sources? How is this sub-divided?*
5.5 mSv
3.1 mSv medical
2.3 mSv background
0.1 mSv human-made radiation
artificial (man-made) radiation sources; which is the largest
medical imaging, nuclear fallout, consumer products
medical imaging is largest
between time, distance, and shielding, which is the most effect mother of personnel protection
distance
minimum lead equivalent
lead aprons
0.5 mm Pb
minimum lead equivalent
lead aprons for fluoro/mobile
0.25 mm Pb
minimum lead equivalent
gloves
0.25 mm Pb
minimum lead equivalent
thyroid shield
0.5 mm Pb
minimum lead equivalent
glasses
0.35 mm Pb
minimum lead equivalent
bucky slot cover
0.25 mm Pb
minimum lead equivalent
spot film device protective curtain
0.25 mm Pb
minimum lead equivalent
clear lead-plastic overhead protective barrier
0.5 mm Pb
primary protective barriers are those surfaces that ________________, located __________ to the primary beam
can be struck by the primary beam, perpendicular
primary protective barriers require ______ of (aluminum/lead) equivalent
1/16 inch, lead
if the primary barrier is a wall, the lead requirement must extend ____________ up from the floor
7 feet (2.3 meters)
occupancy factor controlled area: exposure rate must be no greater than ______
100 mR/week
occupancy factor uncontrolled area: exposure rate must be no greater than ______
10 mR/week or .1 mGy/week
secondary protective barriers are those surfaces that ________________
are struck with stray radiation (leakage and scatter)
secondary barriers that are located parallel to the primary beam require _____ of (aluminum/lead) equivalent
1/32 inch, lead
_______ of the secondary barrier must overlap the primary barrier where the two meet
1/2 inch
maximum exposure rate of table top of a fluoro unit is ______, or cannot exceed _____ for each mA of operation at 80 kVp
10 R/minute, 2.1 R/minute
fluoro function designed to maintain a predetermined level of light intensity exiting the image intensification tube
automatic brightness control (ABC)
1 rem = ___ mSv
10 mSv
decreasing the pulsed fluoroscopy frame rate can (increase/decrease) patient’s radiation dose**
decrease
in direct action of radiation, the x-ray hits which part of the cell?
DNA molecule
lethal effects to the zygote/embryo/fetus are most likely in which stage of pregnancy?
germinal
what type of chromosome break is most easy to repair?
small base pair lesion
what type of chromosome break is most difficult to repair?
double strand break
the relationship between the DAP and field size is _______
directly proportional
coherent interactions occur with a beam carrying ____________ of energy
less than 10 keV
how soon can short term effects of radiation exposure be seen?
within minutes
does coherent scattering result in ionization?
no
which of the following is most effective in reducing patient dose during a radiographic procedure?
use lead apron
use a high kVp
collimate to area of interest
increase distance between tube and patient
collimate to area of interest
inherent filtration (increases/decreases) the need for additional filtration. why is this?
decreases; x-ray divergence/reduction in beam intensity
wavelength is the _____________ between _________________
distance, two successive peaks of an electromagnetic photon
frequency is the ________________________ and is measured in the unit ___________
rate of rise and fall (oscillation) of the EM photon, Hertz (Hz)
How does increasing energy affect frequency & wavelength?
increase frequency, decrease wavelength
does the velocity of an x-ray photon ever change?
no, it stays the same (frequency and wavelength can change, but the speed is the same)
What interaction is responsible for patient dose?
photoelectric
What is responsible for tech dose?
Compton
total absorption of the x-ray photon
photoelectric interaction
partial absorption of the x-ray phton
Compton interaction
memory trick for remembering measurement information
The A’s have Grays (Gy)
The E’s Have V’s ( Sievert Sv)
If there is a Q it multiplies 2 (Equivalent dose)
thermionic emission requires _____ amps of current
4 to 6 amps
x-ray production is ___% heat and ___% x-rays
99% heat, 1% x-rays
__% of x-rays are produced with Bremsstrahlung interactions and (~) remaining are with ___________
90%, characteristic
accumulated dose record purpose provides an indication of working habits for works that can potentially be exposed to ___% of the annual total effective dose limit
25
how long must accumulated dose records by kept?
as long as the worker is employed in medical imaging
what type of dosimeter is least sensitive to radiation?
film badge
radiation monitoring devices should be worn if the radiation worker is at risk of receiving __% of the annual ____________________ limit of ___ rem
10%, annual effective absorbed dose equivalent, 5.0 rem
NCRP recommendation exposure limits
annual whole body exposure
in mSv
in rem
50 mSv
5.0 rem
NCRP recommendation exposure limits
lens of the eye
in mSv
in rem
150 mSv
15 rem
NCRP recommendation exposure limits
all other areas (red bone marrow, breast, lung, extremities, etc.)
in mSv
in rem
500 mSv
50 rem
NCRP recommendation exposure limits
cumulative effective limit
1 rem x age in years
(10 mSv x age in years)
annual effective dose equivalent limit for public = ____
annual effective dose equivalent limit for occupational = ____
public = 0.5 rem
occupational = 5 rem
annual effective dose equivalent limit for public = ____
in mSv
in rem
5 mSv
0.5 rem
embryo/fetus exposure level limit for entire pregnancy
in mSv
in rem
5 mSv (0.5 rem) for entire pregnancy
embryo/fetus exposure level limit per month**
in mSv
in rem
0.5 mSv, 0.05 rem
what does DEL stand for in radiation safety?
dose equivalent limit
what is DEL a newer version of?
maximum permissible dose
what is dose equivalent limit/maximum permissible dose?
the maximum dose of radiation that in light of present knowledge would be be expected to yield any significant radiation effects
radiation limits fetus total = _____, Fetus monthly = _______ (pregnancy is 10 months)
fetus total = 5 mSv, fetus monthly = 0.5 mSv
Student radiographer dose = _____
1 mSv
