MC Chapter 14

Foreshortening is a form of: a. magnification b. noise c. umbra d. distortion e. artifact

distortion

The complete or "true" image shadow of a radiographic image is called its: a. penumbra b. edge gradient c. umbra d. parallax e. density trace

umbra

As the penumbra of an image spreads, the: a. umbra grows also b. umbra shrinks c. umbra remains unaffected d. image becomes distorted e. image becomes magnified

umbra shrinks

The formula FS X OID/SOD is used to calculate the in a radiographic image: a. unsharpness b. sharpness c. magnification d. distortion e. noise

unsharpness

Which of the following is equivalent to low sharpness: a. high umbra b. low brightness c. good blur d. short gray scale e. high penumbra

high penumbra

Which of the following is equivalent to low penumbra: a. low sharpness b. high sharpness c. high blur d. low distortion e. low magnification

high sharpness

The unsharpness in an image is produced by all of the following except: a. mAs b. SOD c. OID d. focal spot size

mAs

The recognizability or geometrical functions in an image include all of the following except: a. sharpness b. magnification c. distortion d. noise

noise

The overall resolution of an image depends upon: a. sharpness b. contrast c. visibility d. geometrical integrity e. all of the above

all of the above

The projected image of a bone on a radiograph is twice as wide, but three times as long as the real bone. The image is: a. magnified b. distorted c. unsharp d. both a & b e. both b & c

both a & b

For the image of an object to be shape distorted, its length and its width must be altered by: a. off-centering b. one being reduced, the other increased c. the same degree d. different degrees

different degrees

An object being radiographed measures 4 cm in width. The SID used was 100 cm and the object was located 60 cm above the image receptor plate. How big is the projected image? a. 4 cm b. 6.7 cm c. 8 cm d. 10 cm e. 12 cm

10 cm

What is the relative sharpness for an SOD of 70 cm and an OID of 10 cm? a. 7 b. 3.3 c. 0.14 d. 1.17 e. 0.85

7

Which of the following formulas would be correct for calculating the relative sharpness of a projected image? a. SID/SID-OID b. SID/OID c. SOD/OID d. SID-OID/SOD

SOD/OID

What is the amount of unsharpness for a projection taken with an 0.3 mm focal spot, 76 cm SOD and 4 cm OID? a. 0.63 mm b. 0.016 mm c. 1.6 mm d. 0.8 mm e. 5.7 mm

0.016 mm

What is the amount of unsharpness for a projection taken with an 0.5 mm focal spot, 150 cm SOD and 15 cm OID? a. 5 mm b. 10 mm c. 20 mm d. 0.5 mm e. 0.05 mm

0.05 mm

An original exposure used an SOD of 80 cm and an OID of 4 cm. If the OID is increased to 6 cm, to what fraction of the original sharpness will the sharpness be reduced? a. 0.13 b. 0.25 (1/4) c. 0.67 (2/3) d. 0.75 (3/4)

0.67 (2/3)

When a 1 mm focal spot is used with an SID of 100 cm and an OID of 50 cm, the amount of penumbra present in the image will be: a. 1 mm b. 2 mm c. 0.5 cm d. 0.2 mm e. 0.5 mm

1 mm

With an SID of 100 cm, and an OID of 25 cm, what is the factor of magnification? a. .25 X b. 3 X c. 1.33 X d. 4 X e. 2 X

1.33 X

An object is projected using an SID of 180 cm and an SOD of 135 cm. If the projected image measures 20 cm in length, how big must the object have been? a. 20 cm b. 15 cm c. 12 cm d. 26 cm

15 cm

The ability to distinguish two adjacent details as being separate and distinct from each other defines image: a. contrast b. sharpness c. resolution d. visibility

resolution

As one visually scans across an image, the abruptness with which the edges of a particular image "stop" would define the image's: a. sharpness b. unsharpness c. resolution d. distortion e. contrast

sharpness

Which of the following should always be maximized: a. brightness b. contrast c. magnification d. elongation e. sharpness

sharpness

The amount of penumbra that will be produced in a radiographic projection can be predicted using penumbra diagrams, and is based mathematically upon: a. solid geometry b. similar triangle geometry c. signal-to-noise ratio d. modulation transfer function

similar triangle geometry

Penumbra occurs in all radiographic images because: a. object-image receptor distances cannot be avoided b. x-rays emanate from an area source c. x-rays are emitted from a point source d. some degree of scatter radiation is always present e. some degree of motion cannot be avoided

x-rays emanate from an area source