Exposure Quiz #3 ( SA8-12)

Calculate the magnification factor when the SID is 40 in. and the SOD is 25 in.

1.6

After completing a radiograph using 27 mAs at 90 kVp, the image demonstrates adequate overall density but an area that is underpenetrated. In order to produce an optimum image in terms of contrast and penetration, the repeat image should be taken at

13 mAs and 104 kVp

If a projected image measures 3 in. and the magnification factor is 1.1, what is the size of the actual object?

2.7

Calculate the magnification factor when the SID is 72 in. and the SOD is 25 in.

2.9

If an object measures 2 cm and the image measures 3 cm, what would be the percent magnification of the object?

50%

Optimum exposure to an IR is A. 1 mR plus or minus 33% B. 10 mR plus or minus 33% C. 1 mR plus or minus 3% D. 10 mR plus or minus 15%

A. 1 mR plus or minus 33%

What conclusion can you reach regarding an image with an S# of 750 and good radiographic image density on the display monitor? A. The image is likely to demonstrate noise or quantum mottle B. There was not enough exposure to create a good histogram C. The noise level will be at a minimum and the image will look good in the magnification mode D. The IR received too much exposure

A. The image is likely to demonstrate noise or quantum mottle

A renal calculus that measures 0.2 mm in size A. cannot be visualized with an effective focal spot of 0.5 mm focal spot due to penumbral overlap B. is best seen with magnification and a large focal spot C. most likely will be visualized with a small radiographic tube angle using a large target angle D. all of the above

A. cannot be visualized with an effective focal spot of 0.5 mm focal spot due to penumbral overlap

The density maintenance formula mathematically resembles the A. inverse square law B. 15% rule C. law of reciprocity D. none of the above

A. inverse square law

Which factor influences the average energy of photons reaching the IR? A. kVp B. mAs C. focal spot size D. mA

A. kVp

Which generator produces the least amount of radiographic density per mAs? A. single-phase, 2-pulse B. three-phase, 6-pulse C. three-phase, 12-pulse D. a high-frequency generator

A. single-phase, 2-pulse

The ______ represents a depth to the information in the digital image. A. z axis B. y-x grid matrix C. y axis D. x-y grid matrix

A. z axis

The optical density range visible to the human eye is: A. 0.025 to 0.25 B. 0.25 to 2.50 C. 2.50 to 20.50 D. 20.50 to 200.50

B. 0.25 to 2.50

The magnification factor for a radiographic procedure is calculated at 1.25. It may be assumed that there is a ____magnification of the object size. A. 25% B. 125% C. 0.25% D. 1.25%

B. 125%

The minimum change necessary to cause a visible shift in density is ____ percent of mAs. A. 10-12 B. 25-35 C. 50-60 D. none of the above

B. 25-35

As the spatial frequency of objects increases, A. MTF increases proportionally B. MTF decreases C. MTF increases D. MTF computes to a value of 1

B. MTF decreases

Resolution is improved when A.OID increases B.SID increases C.SID decreases D.the receptor is angled

B. SID Increases

Which radiograph exhibits the best detail? A. a PA chest radiograph for evaluation of the heart at 40 in B. a PA chest radiograph for evaluation of the heart at 72 in C. an AP chest radiograph for evaluation of the heart at 40 in D. an AP chest radiograph for evaluation of the heart at 72 in

B. a PA chest radiograph for evaluation of the heart at 72 in

In general radiography, quantum noise is A. filtered out of images B. a function of mAs and kVp C. designed into the receptor specifications D. a recorded detail parameter

B. a function of mAs and kVp

The concept of contrast as it is displayed on a soft-copy monitor for digital images is described as A. window width B. dynamic range C. contrast width D. window range

B. dynamic range

The___ the SID, the ___the magnification. A. greater; larger B. greater; smaller C. lesser; smaller D. SID has no effect on magnification

B. greater; smaller

Focal spot blooming occurs with A. high kVps B. high mAs C. large SIDs D. extreme tube angulation

B. high mAs

In digital imaging systems , increasing sampling frequency of the data A. increases dose B. increases image fidelity C. decreases MTF D. decreases dose

B. increases image fidelity

Examinations of body parts with a large inherent OID warrant a _____whenever possible. A. small SID B. large SID C. small SOD D. large focal spot

B. large SID

A radiograph that demonstrates minimal differences between density shades is called A. short scale B. low contrast C. high contrast D. all of the above

B. low contrast

Which measures the accuracy of an image compared to the original object on a scale of 0 to 1? A. line spread function B. modulation transfer function C. point spread function D. noise reduction function

B. modulation transfer function

A fluoroscopic examination that uses barium as a contrast material would typically produce images with A. long scale contrast B. short scale contrast C. low contrast D. both a and c

B. short scale contrast

When the sampling frequency is less than the Nyquist value, A.aliasing is eliminated B.the Moire effect can occur C.patient dose must increase D.the Nyquist value must be altered

B. the Moire effect can occur

A pixel bit depth of 2^16 will demonstrate ________shades of gray A. 16 B. 32 C. 65,536 D. none of the above

C. 65,536

Radiographic room A is a three-phase, 6-pulse generator. Room B is a high frequency generator. When going between these two rooms to perform examinations, what exposure modification is necessary to produce comparable density/IR exposure? A. Use 15% more with the three-phase system B. Use 10% more with the high frequency system C. No change is required between the two systems D. Use 10% less with the high frequency system

C. No change is required between the two systems

When digital imaging receptors are used, A. kVp is not a consideration B. radiographic grids are not necessary C. an exposure at 90 kVp would require a grid D. Compton scatter is not a factor

C. an exposure at 90 kVp would require a grid

A radiograph that demonstrates considerable differences between densities is called A. long scale B. low contrast C. high contrast D. all of the above

C. high contrast

The greatest factor in the production of scatter radiation is A. kVp B. mAs C. patient thickness D. patient position

C. patient thickness

Proper alignment is achieved when the central ray is ____to the part and ____to the image receptor. A. perpendicular; parallel B. parallel; perpendicular C. perpendicular; perpendicular D. parallel; parallel

C. perpendicular; perpendicular

A digital detector with a high fill factor A. will produce poor resolution B. will require longer processing time C. will produce high resolution D. is undesirable

C. will produce high resolution

Which statement is FALSE? A. As mAs increases, exposure increases B. As mAs decreases, density decreases C. As mAs increases, density increases D. As mAs decreases, exposure increases

D. As mAs decreases, exposure increases

Which generator produces the greatest amount of radiographic density per mAs? A. single-phase, 2-pulse B. three-phase, 6-pulse C. three-phase, 12-pulse D. a high-frequency generator

D. a high-frequency generator

A radiograph that demonstrates considerable differences between densities is called A. short scale B. high contrast C. increased contrast D. all of the above

D. all of the above

As focal spot size decreases, A. umbra is improved B. penumbra decreases C. resolution increases D. all of the above

D. all of the above

Large patients receive a greater exposure than small patients because their A. SOD is decreased B. OID is increased C. entrance skin surface is closer to the source D. all of the above

D. all of the above

Size distortion is controlled by A. SID B. OID C. radiographic distances D. all of the above

D. all of the above

The recorded detail of a radiographic image is visible because of A. sufficient contrast B. sufficient density C. window level D. both a and b

D. both a and b

Factors affecting recorded detail include A. kVp B. radiographic grids C. mAs D. focal spot size

D. focal spot size

Which generator type results in the greatest decrease in contrast? A. single-phase, 2-pulse B. three-phase, 6-pulse C. three-phase, 12-pulse D. high frequency

D. high frequency

The relationship between exposure and SID is A. directly proportional B. inversely proportional C. directly proportional to the square of the distance D. inversely proportional to the square of the distance

D. inversely proportional to the square of the distance

Which type of radiograph provides the most information? A. an image with quantum mottle B. high contrast images C. low density images D. low contrast images

D. low contrast images

Spatial resolution in digital imaging is determined by the A.bit depth B.matrix size C.pixel size D.all of the above

D.all of the above

how is percent magnification calculated?

I-O/O *100

Inverse square law

I1/I2=D2^2/D1^2

How is the magnification factor calculated?

SID/SOD

How is object size calculated?

image size/Magnification factor

Grid Conversion Factor (GCF)

mAs with grid/mAs without grid

Direct square law

mAs1/mAs2=D1^2/D2^2

Grid conversion formula

mAs1/mAs2=GCF1/GCF2