Week 3 Comprehensive Radiology Review Questions

Front 1

The term effective dose refers to

A. whole-body dose.B. localized organ dose.C. genetic effects.D. somatic and genetic effects

Back 1

A. whole-body dose.

Front 2

Which of the following types of adult tissues is (are) relatively insensitive to radiation exposure?

1. Muscle tissue
2. Nerve tissue
3. Epithelial tissue

Back 2

1 and 2 only

Front 3

The squeegee assembly in an automatic processor

1. functions to remove excess solution from films.
2. is located near the crossover rollers.
3. helps establish the film's rate of travel

Back 3

1 and 2 only

Front 4

Resolution in computed radiography increases as

1. laser beam size decreases
2. monitor matrix size decreases
3. PSP crystal size decreases

Back 4

1 and 3 only

Front 5

Which of the following groups of exposure factors will produce the longest scale of contrast?

A. 200 mA, 0.25 second, 70 kVp, 12:1 gridB. 500 mA, 0.10 second, 90 kVp, 8:1 gridC. 400 mA, 0.125 second, 80 kVp, 12:1 gridD. 300 mA, 0.16 second, 70 kVp, 8:1 grid

Back 5

500 mA, 0.10 second, 90 kVp, 8:1 grid Of the given factors, kilovoltage and grid ratio will have a significant effect on the scale of radiographic contrast. The mAs values are almost identical. Because an increased kilovoltage and low-ratio grid combination would allow the greatest amount of scattered radiation to reach the IR, thereby producing more gray tones, B is the best answer. Group D also uses a low-ratio grid, but the kilovoltage is too low to produce as many gray tones as B.

Front 6

A satisfactory radiograph was made using a 40-inch SID, 10 mAs, and a 12:1 grid. If the examination will be repeated at a distance of 48 inches and using an 8:1 grid, what should be the new mAs to maintain the original density?

A. 5.6B. 8.8C. 11.5D. 14.4

Back 6

C. 11.5

Front 7

The device that is used for the direct measurement of optical density is the

A. sensitometer.B. densitometer.C. penetrometer.D. H&D curve.

Back 7

B. densitometer

Front 8

A film emerging from the automatic processor exhibits excessive density. This may be attributable to which of the following?

1. Developer temperature too high
2. Chemical fog
3. Underreplenishment

Back 8

1 and 2 only

Front 9

Which of the following technical changes would best serve to remedy the effect of widely different tissue densities?

A. Use of high-speed screensB. Use of a high-ratio gridC. High kVp exposure factorsD. High mAs exposure factors

Back 9

High kVp exposure factors

Front 10

Grid cutoff due to off-centering would result in

A. overall loss of density.B. both sides of the image being underexposed.C. overexposure under the anode end.D. underexposure under the anode end

Back 10

overall loss of density.

Front 11

Which of the following groups of exposure factors would be most effective in eliminating prominent pulmonary vascular markings in an RAO position of the sternum?

A. 500 mA, 1/30 second, 70 kVpB. 200 mA, 0.04 second, 80 kVpC. 300 mA, 1/10 second, 80 kVpD. 25 mA, 7/10 second, 70 kVp

Back 11

25 mA, 7/10 second, 70 kVp In the RAO position, the sternum must be visualized through the thorax and heart. Prominent pulmonary vascular markings can hinder good visualization. A method frequently used to overcome this problem is to use an mAs with a long exposure time. The patient is permitted to breathe normally during the (extended) exposure and, by doing so, blurs out the prominent vascularities

Front 12

Which of the following is an abnormal intensifying screen action?

A. FluorescenceB. LuminescenceC. SpeedD. Lag

Back 12

lag

Front 13

According to the line focus principle, an anode with a small angle provides

1. improved recorded detail.
2. improved heat capacity.
3. less heel effect.

Back 13

1 and 2 only

Front 14

The effect that differential absorption has on radiographic contrast of a high subject contrast part can be minimized by

1. using a compensating filter.
2. using high-kVp exposure factors.
3. increased collimation.

Back 14

1 and 2 only

Front 15

What unit of measurement expresses the amount of energy deposited in tissue?

A. Roentgen (C/kg)B. Rad (Gy)C. Rem (Sv)D. RBE

Back 15

B. Rad (Gy)EXPLANATION: The rad is the unit of absorbed dose. It is equal to 100 ergs of energy per gram of any absorber. The roentgen measures quantity of ionization in air. The rem and RBE express radiation dose to biologic material. (Bushong, p 23)

Front 16

According to the NCRP, the annual occupational whole-body dose equivalent limit for students under age 18 is

A. 1 mSvB. 50 mSvC. 150 mSvD. 500 mSv

Back 16

1 mSv

Front 17

Which of the following would be the safest interval of time for a fertile woman to undergo abdominal radiography without significant concern for irradiating a recently fertilized ovum?

A. The first 10 days following the cessation of menstruationB. The first 10 days following the onset of menstruationC. The 10 days preceding the onset of menstruationD. About 14 days before menstruation

Back 17

B. The first 10 days following the onset of menstruation

Front 18

The correct way(s) to check for cracks in lead aprons (are)

1. to fluoroscope them once a year.
2. to radiograph them at low kilovoltage twice a year.
3. by visual inspection.

Back 18

1 only

Front 19

The annual dose limit for occupationally exposed individuals is valid for

A. alpha, beta, and x-radiations.B. x- and gamma radiations only.C. beta, x-, and gamma radiations.D. all ionizing radiations.

Back 19

C. beta, x-, and gamma radiations.

Front 20

What is used to account for the differences in tissue sensitivity to ionizing radiation when determining effective dose (E)?

1. Tissue weighting factors (Wt)

2. Radiation weighting factors (Wr)

3. Absorbed dose

Back 20

1 only

Front 21

The unit of absorbed dose is the

A. roentgen (C/kg).B. rad (Gy).C. rem (Sv).D. RBE.

Back 21

B. rad (Gy).

Front 22

According to the NCRP, the annual occupational whole-body dose equivalent limit is

A. 1 mSv.B. 50 mSv.C. 150 mSv.D. 500 mSv.

Back 22

50 mSv.

Front 23

Which of the following tissues or organs is the most radiosensitive?

A. RectumB. EsophagusC. Small bowelD. Central nervous system (CNS)

Back 23

Small bowel

Front 24

What is the relationship between LET and RBE?

B. As LET increases, RBE decreases
C. As LET decreases, RBE increases
D. There is no direct relationship between LET and RBE.

Back 24

A. As LET increases, RBE increases

Front 25

The photoelectric effect is the interaction between x-ray photons and matter that is largely responsible for patient dose. The photoelectric effect is likely to occur under which of the following conditions?

1. With absorbers of high atomic number
2. With low-energy incident photons
3. With the use of positive contrast media

Back 25

1, 2, and 3

Front 26

Primary radiation barriers must be at least how high?

A. 5 feetB. 6 feetC. 7 feetD. 8 feet

Back 26

7 feet

Front 27

Fractional-focus tubes, with a 0.3-mm focal spot or smaller, have special application in

A. magnification radiography.B. fluoroscopy.C. tomography.D. image intensification.

Back 27

Magnification radiography may be used to demonstrate small, delicate structures that are difficult to image with conventional radiography. Because object-image distance (OID) is an integral part of magnification radiography, the problem of magnification unsharpness arises. The use of a fractional focal spot (0.3 mm or smaller) is essential to the maintenance of image sharpness in magnification films. Radiographic rating charts should be consulted, as the heat load to the anode may be critical in magnification radiography. The long exposures typical of image-intensified fluoroscopy and tomography make the use of a fractional focal spot generally impractical and hazardous to the anode.

Front 28

Which of the following will improve the spatial resolution of image-intensified images?

1. A very thin coating of cesium iodide on the input phosphor
2. A smaller-diameter input screen
3. Increased total brightness gain

Back 28

1 and 2 only

Front 29

How is the thickness of the tomographic section related to the tomographic angle?

A. The greater the tomographic angle, the thicker the section.B. The greater the tomographic angle, the thinner the section.C. The less the tomographic angle, the thinner the section.D. The tomographic angle is unrelated to section thickness.

Back 29

The answer is B.

EXPLANATION: Tomography is a procedure that uses reciprocal motion between the x-ray tube and the film to image structures at a particular level in the body, while blurring everything above and below that level. The thickness of the level visualized can be varied by changing the tube angle (amplitude). In general, the greater the tube angle, the thinner the section imaged. Thinner sections may be used for imaging small or intricate structures.

Front 30

The image intensifier's input phosphor differs from the output phosphor in that the input phosphor

A. is much larger than the output phosphor.B. emits electrons whereas the output phosphor emits light photons.C. absorbs electrons whereas the output phosphor absorbs light photons.D. is a fixed size, and the size of the output phosphor can vary.

Back 30

A. is much larger than the output phosphor.
The image intensifier's input phosphor is six to nine times larger than the output phosphor. It receives the remnant radiation emerging from the patient and converts it into a fluorescent light image. Very close to the input phosphor, separated only by a thin transparent layer, is the photocathode. The photo- cathode is made of a photoemissive alloy, usually a cesium and antimony compound. The fluorescent light image strikes the photocathode and is converted to an electron image, which is focused by the electrostatic lenses to the small output phosphor.

Front 31

Off-focus, or extrafocal, radiation may be minimized by

A. avoiding the use of very high kilovoltages.B. restricting the x-ray beam as close to its source as possible.C. using compression devices to reduce tissue thickness.D. avoiding extreme collimation.

Back 31

The answer is B.

EXPLANATION: Off-focus, or extrafocal, radiation is produced as electrons strike metal surfaces other than the focal track and produce x-rays that emerge with the primary beam at a variety of angles. This radiation is responsible for indistinct images outside the collimated field. Mounting a pair of shutters as close to the source as possible minimizes off-focus radiation.

Front 32

Which of the following is the correct formula for determining heat units for a three-phase, 12-pulse x-ray machine?

A. kVp x mA x timeB. mA x kVp x mAsC. kVp x mAs x 1.35D. mA x time x kVp x 1.41

Back 32

D.
Each time an x-ray exposure is made, heat is produced in the x-ray tube. Actually, of all the energy used to make an exposure, 99.8% is converted to heat and only 0.2% is converted to x-ray photon energy. Since greater heat production leads to increased wear and tear on the x-ray tube, thereby decreasing its useful life, it behooves the radiographer to be able to calculate HU and to understand the means of keeping heat production to a minimum. HU for a single-phase x-ray unit are determined by using the formula HU = mA x kVp x time. HU for a three-phase, six-pulse x-ray unit are determined by using the formula: HU = mA x kVp x time x 1.35. HU for a three-phase, 12-pulse x-ray unit are determined by using the formula: HU = mA x kVp x time x 1.41. High-mAs technical factors produce far more heat units than low-mAs technical factors.

Front 33

If 85 kV and 20 mAs were used for a particular abdominal exposure with single-phase equipment, what mAs would be required to produce a similar radiograph with 3-phase, 12-pulse equipment.

A. 40B. 25C. 20D. 10

Back 33

The answer is D.

EXPLANATION: Single-phase radiographic equipment is much less efficient than three-phase equipment because it has a 100% voltage ripple. With three-phase equipment, voltage never drops to zero, and x-ray intensity is significantly greater. To produce similar density, only two thirds of the original mAs would be used for three-phase, six-pulse equipment (2/3 x 20 = 13 mAs). With 3-phase, 12-pulse equipment, the original mAs would be cut in half; thus, 10 mAs should be used.