Radiation Protection Flashcards
What is used to account for the differences in tissue sensitivity to ionizing radiation when determining effective dose E?
Tissue Weighing Factor
According to the National Council on Radiation Protection and Measurements (NCRP), the monthly gestational dose-equivalent limit for embryo/fetus of a pregnant radiographer is
5 mSv
A time of 1.5 minutes is required for a particilar fluoroscopic examination, whose exposure rate is 275 mR/h. What is the approximate radiation exposure for the radiologic staff present in the fluoroscopy room during the examination?
6.87 mR
275(mR) = x (mR)
———— ———-
60 (min) 1.5 (min)
60x = 412.5 x = 6.87 mR dose in 1.5 mins
If the exposure rate to an individual standing 4m from a source of radiation is 10mR/h, what will be the dose received after 20 minutes at a distance of 6m from the source?
1.48 mR
I1 = D2(2) --- -------- I2 D1(2)
10 = 36
— —-
x 16
36x = 160
x = 4.44
All the ff statements regarding the mobile radiographic equipment are true except
exposure switches must be the two-stage type
- the exposure cord must permit the operator to stand at least 6 ft from the px, x-ray tube, and useful beam
- a lead apron should be carried with the unit and worn by the radiographer during exposure
- the radiographer must alert individuals in the area before making the exposure
Which of the ff cell types has the greatest radiosensitivity in the adult human?
Lymphocytes
Guidelines for the use of protective shielding state that gonadal shielding should be used
- if the patient has reasonable reproductive potential
* when the gonads are within 5cm of the collimated field
The interaction between ionizing radiation and the target molecule taht is most likely to occur is the
indirect effect
What is the approximate entrance skin exposure (ESE) for the average AP supine abdomen radiograph?
300 mrad
All of the ff device(s) are generally used to help reduce patient dose except
grid
How will xray photon intensity be affected if the source-to-image distance (SID) is doubled?
Its intensity decreases four times
What is the established annual occupational dose-equivalent limit for the lens of the eye?
150mSv
Occupational radiation monitoring is required when it is possible that the individual might receive more than
one-tenth the annual dose
Sources of natural background radiation contributing to whole body radiation dose include
- terrestrial radionuclides
* internal radionuclides
Irradiation of water molecules within the body and their resulting breakdown is termed
radiolysis
Which of the ff contributes most to occupational exposure?
Compton scatter
Which of the ff is (are) used to account for the differences in tissue characteristics when determining effective dose to biologic material?
Tissue Weighing Factor
The x-ray interaction with the matter that is responsible for the majority of scattered radiation reaching the IR is
Compton scatter
The exposure rate to a body 4 ft from a source of radiation is 16R/h. What distance from the source would be necessary to decrease the exposure to 6R/h?
7 ft
16 R/h = X2 --------- ---- 6 R/h 16 6x(2) = 256 x(2) = 42.66
With milliamperes (mA) increased to maintain output intensity, how is the ESE affected as the SSD is increased?
The ESE increases
Late radiation-induced somatic effects include
- thyroid cancers
- cataractogenesis
- genetic mutations
Each time an x-ray beam scatters, its intensity at 1 m from the scattering object is what fraction of its original intensity?
1/1000
According to NCRP, the annual occupational whole-body dose-equivalent limit is
50 mSv
A thermoluminiscent dosimetry system would use which of the following crystals?
Lithium fluoride
Sources of secondary radiation include
- background radiation
- leakage radiation
- scatterred radiation
leakage radiation & scaterred radiation
All the following have an effect on patient dose except
focal spot size
- kilovoltage
- milliampere-seconds
- inherent filtration
The photoelectric effect is more likely to occur with
- absorbers having a high Z number
- high-energy incident photons
- positive contrast media
absorbers having high Z number
positive contrast media
All the ff radiation-exposure responses exhibit a nonlinear threshold dose-response relationship except
leukemia
- skin erythema
- hematologic depression
- radiation lethality
In radiation protection, the product of absorbed dose and the correct modifying factor (radxQF) is used to determine
rem (Sv)
Which of the ff is recommended for the pregnant radiographer
Wear a second dosimeter under the lead apron
The annual dose limit for medical imaging personnel includes radiation from
- occupational exposure
- background radiation
- medical x-rays
occupational exposure
Which of the ff anomalies is (are) possible if an exposure dose of 40 rad (400mGy) were delivered to a pregnant uterus in the third week of pregnancy?
Organ anomaly
The effects of radiation on biologic material depend on several factors. If a quantity of radiation is delivered to a body over a long period of time, the effect
will be less than if it were delivered all at one time
Medical and dental radiation accounts for what percentage of the general public’s exposure to human-made radiation?
90%
Which of the ff is (are) composed of nondividing, differentiated cells?
- neurons and neuroglia
- epithelial tissue
- lymphocytes
neurons and neuroglia
How does filtration affect the primary beam?
It increases the average energy of the primary beam.
What is the minimum lead requirement for lead apron, according to the NCRP?
0.50 mm Pb
An optically stimulated luminescence dosimeter contains which of the ff detectors?
Aluminum oxide
Immature cells are referred to as
- undifferentiated cells
* stem cells
What is the term used to describe x-ray photon interaction with matter and the transference of part of the photon’s energy to mater?
Scattering
What is the approximate ESE for the average upright PA chest radiograph using 115 kVp and a grid?
20 mrad
To be in compliance with the radiation safety standards, the fluoroscopy exposure switch must
terminate fluoro after 5 mins
Primary radiation barriers must be at least how high?
7 ft
The annual dose limit for occupationally exposed individuals is valid for
beta, x-, and gamma radiations
Patient dose increases as fluoroscopic
FOV decreases
Types of gonadal shielding include which of the ff?
- flat contact
- shaped contact (contour)
- shadow
all of them
What unit of measure is used to express ionizing radiation dose to biologic material?
Rem (Sv)
LET is best defined as
- a method of expressing radiation quality
* a measure of the rate at which radiation energy is transferred to soft tissue
For exposure to 1 rad of each of the ff ionizing radiations, which would result in the greatest dose to the individual?
c
For exposure to 1 rad of each of the ff ionizing radiations, which would result in the greatest dose to the individual?
Internal source of alpha particles
The skin response to radiation exposure that appears as hair loss is known as
epilation
Biologic material is least sensitive to irradiation under which of the ff conditions?
Anoxic
The reduction in the intensity of an xray beam as it passes through the material is termed?
attenuation
Which type of dose-response relationship represents radiation-induced leukemia and genetic effects?
Linear, nonthreshold
A dose of 25 rad to the fetus during the seventh or eighth week of pregnancy is likely to cause which of the ff?
Neurologic anomalies
Late effects of radiation, whose incidence is dose related and for which there is no threshold dose, are referred to as
stochastic
Which of the ff methods can be used to reduce radiation exposure to a recently fertilized ovum?
Elective booking
Patient questionnaire
The 10-day rule
Classify the ff tissues in order of increasing radiosensitivity:
- Liver cells
- Intestinal crypt cells
- Muscle cells
3, 1, 2
The largest amount of diagnostic xray absorption is most likely to occur in which of the ff tissues?
Bone
According to NCRP regulations, leakage radiation from the x-ray tube must not exceed
100mR/h
Which of the ff most effectively minimizes the radiation exposure to the patient?
High speed intensifying screen
Which of the ff statements is (are) true with respect to radiation safety in fluoroscopy?
- Tabletop radiation intensity must not exceed 2.1 R/min/mA
- Tabletop radiation intensity must not exceed 10 R/min
- In high-level fluoroscopy, tabletop intensity up to 20 R/min is permitted.
all of the above
The symbol 130/56 Ba and 138/56 are examples of which of the ff?
isotopes
Which of the ff account(s) for an x-ray beam’s heterogenecity?
All of the above
Which of the ff factors will affect both the quality and the quantity of the primary beam?
- HVL
- kV
- mA
HVL and kV
Diagnostic x-radiation may be correctly described as
low energy, low LET
Primary radiation barriers usually require which thickness of shielding?
1/16-in. lead
Which of the following groups of exposure factors will deliver the least patient dose? 300 mA, 250 ms, 70 kVp 300 mA, 125 ms, 80 kVp 400 mA, 90 ms, 80 kVp 600 mA, 30 ms, 90 kVp
600 mA, 30 ms, 90 kVp
For radiographic examinations of the skull, it is generally preferred that the skull be examined in the
PA Projection
According to the NCRP, the annual occupational dose-equivalent limit (50 rem) to the thyroid, skin, extremities is
500 mSv
The skin response to radiation exposure, which appear as reddening of the irradiated skin area, is known as
erythema
What is the intensity of scattered radiation perpendicular to and 1 m from a patient compared with the useful beam at the patient’s surface?
0.1%
An increase of 1.0 mm added aluminum filtration of the x-ray beam would have which of the ff effects?
- Increase in average energy of the beam
- Increase in patient skin dose
- Increase in milliroentgen output
Increase in average energy of the beam
Aluminum filtration has its greatest effect om
low energy xray photons
The amount of time that xrays are being produced and directed toward a particular wall is referred to as the
Use factor
The operation of personnel radiation monitoring devices can depend on which of the ff
- Ionization
- Luminescence
- Thermoluminescence
all of them
Which of the ff results from restriction of the xray beam?
- Less scattered radiation production
- Less patient hazard
- Less radiographic contrast
1 & 2
Which acute radiation syndrome requires the largest exposure before any effects become apparent?
CNS