Prelim Flashcards
concerned with providing occupational radiation protection and minimizing dose to the public
health physics
a radiation scientist who is concerned with the research, teaching or operational aspects of radiation safety
health physicist
rationale: the linear non-threshold radiation dose relationship (LNT) for stochastic effects
ALARA
3 cardinal principles
time
distance
shielding
time of exposure should be kept to a minimum
minimize time
radiation dose is ________ related to the duration of exposure
radiation dose is DIRECTLY related to the duration of exposure
it reminds the radiologist that a considerable amount of fluoroscopic time has elapsed
5 minutes reset timer
radiation dose is ________ related to the distance between the source & the patient
radiation dose is INVERSELY related to the distance between the source & the patient
it states that the intensity of radiation at a location is inversely proportional to the square of its distance from the source of radiation
inverse square law
it states that one can compensate for a change in the source-to-object distance by changing the mAs by the factor SID squared
square law
it was used to calculate exposure in radiographic technique
square law
it greatly reduces the level of radiation exposure
shielding
composition of shielding
lead
protective apron is composed of
0.5 mm Pb
it reduces occupational exposure to 25%
protective apron
the thickness of absorber necessary to reduce radiation intensity to half its original value
half value layer
the thickness of absorber necessary to reduce radiation intensity to one-tenth its original value
tenth value layer (TVL)
the equivalent whole body dose
effective dose
it must be contained within protective housing
protective xray tube housing
it reduces leakage radiation
protective xray tube housing
leakage radiation must be less than ____ mR/hr at a distance of 1 m from the protective housing
leakage radiation must be less than 100 mR/hr at a distance of 1 m from the protective housing
it must indicate the condition of exposure
control panel
it must positively indicate when the xray tube is energized
control panel
what collimator should be used for special examination?
cones and diaphragms
light-localized, variable-aperture, rectangular ________ should be provided
light-localized, variable-aperture, rectangular COLLIMATORS should be provided
the xray beam and the light beam must coincide to within _% of the SID
the xray beam and the light beam must coincide to within 2% of the SID
each radiographic tube should be provided with a mechanism
beam alignment
its purpose is to ensure proper alignment of the xray beam and the IR
beam alignment
All general-purpose diagnostic x-ray beams must have a total filtration
(inherent plus added) of at least ____ mm Al when operated above 70 kVp
All general-purpose diagnostic x-ray beams must have a total filtration
(inherent plus added) of at least 2.5 mm Al when operated above 70 kVp
Radiographic tubes operated between 50 and 70 kVp must have at least
____ mm Al filtration
Radiographic tubes operated between 50 and 70 kVp must have at least
1.5 mm Al filtration
At below 50 kVp, a minimum of ____ mm Al total filtration is
required
At below 50 kVp, a minimum of 0.5 mm Al total filtration is
required
For any radiographic technique, the output radiation intensity should be constant form one exposure to another. This is checked by making repeated radiation exposures through the same technique and observing the average variation in radiation intensity.
reproducibility
the exposure switch should be at least _ m from x-ray tube during exposure in mobile x-ray imaging system
the exposure switch should be at least 2 m from x-ray tube during exposure in mobile x-ray imaging system
the variation in x-ray intensity should not exceed _%
the variation in x-ray intensity should not exceed 5%
what does TVL equal to?
3.3 HVL
the features of _________ imaging
systems that follow are usually the intended primarily to reduce patient radiation dose
the features of FLUOROSCOPIC imaging systems that follow are usually the intended primarily to reduce patient radiation dose
the fluoroscopic exposure control should be of the _____ _____ type
the fluoroscopic exposure control should be of the DEAD MAN type
SSD must not less than __ cm on stationary fluoroscopes
SSD must not less than 38 cm on stationary fluoroscopes
SSD must not less that __ cm on mobile fluoroscopes
SSD must not less that 30 cm on mobile fluoroscopes
the fluoroscopic image receptor assembly serves as a _______ _____ _______ and must be 2 mm Pb equivalent
the fluoroscopic image receptor assembly serves as a PRIMARY PROTECTIVE BARRIER and must be 2 mm Pb equivalent
____ should be measured when filtration is unknown
HVL
total filtration
2.5 mm Al
unexposed border should be visible at all heights above the tabletop
automatic collimators
it is moved at the end of the table during fluoroscopy
bucky tray
it should be positioned between fluoroscopist and patient
protective curtain
it produces an audible sound when the fluoroscopic time has exceeded 5 minutes
cumulative timer
the intensity of the x-ray beam at the tabletop of a fluoroscopy should not exceed ___ mGy/min (2.1 R/min) for each mA of operation at 80 kVp
2.1 mGy/min
3 types of radiation
useful
leakage
scater
lead bonded to sheet rock or wood panelling is used most often as a _______ _______ ______
lead bonded to sheet rock or wood panelling is used most often as a PRIMARY PROTECTIVE BARRIER
what can be used instead of lead in primary barrier?
concrete, concrete block or brick
it results when the useful beam intercepts any objects causing some x-rays to be scattered
scatter radiation
radiation emitted from the x-ray tube housing in all directions other than that of the useful beam
leakage radiation
limit of leakage radiation
___ mR/hr at 1 m
100 mR/hr at 1 m
it is designed to shield areas from secondary radiation which is less thick than primary radiation
secondary barrier
composition of secondary barrier
gypsum board
glass
lead acrylic
radiologic technologists receive most of their occupational radiation exposure during __________
radiologic technologists receive most of their occupational radiation exposure during FLUOROSCOPY
The intensity of scattered radiation 1 meter from the patient is approximately ___ % of the intensity of the useful beam at the patient
The intensity of scattered radiation 1 meter from the patient is approximately 0.1 % of the intensity of the useful beam at the patient
6 factors that affect barrier thickness
distance
occupancy
control
workload
use factor
kvp
the use of the area that is being protected
occupancy
an area occupied primarily by radiology personnel & patients
controlled area
an area that can be occupied by anyone
uncontrolled area
product of the maximum mA & the number of x-ray examinations performed per week
workload
the percentage of time during which the x-ray beam is on & directed toward a particular protective barrier
use factor
it is used as a measure of penetrability
kilovolt peak (kVp)
8 radiographic features
protective housing
control panel
collimator
positive beam limitation
filtration
operation shield
mobile x-ray imaging system
