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33 Cards in this Set

  • Front
  • Back
The term effective dose refers to

A. whole-body dose.B. localized organ dose.C. genetic effects.D. somatic and genetic effects
A. whole-body dose.
Which of the following types of adult tissues is (are) relatively insensitive to radiation exposure?

1. Muscle tissue
2. Nerve tissue
3. Epithelial tissue
1 and 2 only
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
1 and 2 only
Resolution in computed radiography increases as

1. laser beam size decreases
2. monitor matrix size decreases
3. PSP crystal size decreases
1 and 3 only
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
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.
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
C. 11.5
The device that is used for the direct measurement of optical density is the

A. sensitometer.B. densitometer.C. penetrometer.D. H&D curve.
B. densitometer
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
1 and 2 only
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
High kVp exposure factors
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
overall loss of density.
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
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
Which of the following is an abnormal intensifying screen action?

A. FluorescenceB. LuminescenceC. SpeedD. Lag
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.
1 and 2 only
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.
1 and 2 only
What unit of measurement expresses the amount of energy deposited in tissue?

A. Roentgen (C/kg)B. Rad (Gy)C. Rem (Sv)D. RBE
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)
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
1 mSv
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
B. The first 10 days following the onset of menstruation
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.
1 only
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.
C. beta, x-, and gamma radiations.
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
1 only
The unit of absorbed dose is the

A. roentgen (C/kg).B. rad (Gy).C. rem (Sv).D. RBE.
B. rad (Gy).
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.
50 mSv.
Which of the following tissues or organs is the most radiosensitive?

A. RectumB. EsophagusC. Small bowelD. Central nervous system (CNS)
Small bowel
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.
A. As LET increases, RBE increases
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
1, 2, and 3
Primary radiation barriers must be at least how high?

A. 5 feetB. 6 feetC. 7 feetD. 8 feet
7 feet
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.
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.
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
1 and 2 only
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.
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.
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.
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.
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.
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.
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
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.
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
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.