1.

A-iv; anodes are positive and attract charged electrons;

B-ii; CsI input phosphors absorb x-rays and emit light;

C-i; light from the input phosphor is absorbed (photoelectric effect) in the photocathode resulting in the emission of electrons.

D-iii; electrons accelerated across the II strike the output phosphor and some of their energy is converted to light.

2

D.

Virtually all IIs have input phosphors made from cesium iodide (CsI).

3

B.

The output phosphor scintillator is made of zinc cadmium sulfide ZnCdS

4

A.

The brightness gain is independent of exposure (i.e., patient dose). Brightness gain is a measure of how much light you get out of the II for a given light level at the input phosphor and is the product of the minification gain and the flux gain.

5.

C

Contrast ratios are typically 20:1; all the other values are representative of modern IIs.

6.

A-iv; II accelerating voltages are in the range of 25 kV to 35 kV;

B-iii; 3 R/min is a typical entrance skin exposure rate in fluoroscopy:

C-ii;

D-i; modern IIs have resolutions in the range of 4 to 5 line pairs/mm.

7

E.

The irradiated input phosphor area is reduced by a factor of four, and the exposure level must be increased fourfold to maintain  the same brightness level at the II output phosphor.

8

B.

The brightness gain is the product of the flux gain and minification gain.  Since the magnification gain is 100 (252/2.52) the flux gain must be 50.

9

A.

Entrance skin exposure rate will increase by a factor of four since only 1/4 of the II is now absorbing x-rays and the light level at the output phosphor has to remain constant.

10

E.

When fields are displayed at a rate of 60/second (30 frames/second), there is no perception of flicker.

11

E.

The 525 lines correspond to 262.5 line pairs but only 70% is achieved in practice (Kell factor of 0.7), resulting in a vertical resolution of 184 line pairs.

12

B.

The bandwidth determines the horizontal TV resolution.

13

C

The number of TV lines is the primary determinant of the vertical TV resolution (525 lines in the United states; 625 lines in Europe).

14

B.

Increasing the kV increases patient penetration and therefore reduces entrance skin dose for a constant II input dose level.

15.

A-ii; typical resolution for a 23-cm II mode;

B-i; the video system will introduce some degradation thus the resolution is slightly less than normal fluoroscopy;

C-iii; a 1,025 line TV will have a resolution twice that of a conventional 525-line fluoroscopy system;

D-iv; the II output always has a better spatial resolution than the TV image.

16

E.

By reducing the II size (field of view) the 525 lines are used to represent smaller distances and the number of line pairs allocated per mm increases.

17

D.

Visibility of low contrast objects improves as scatter rejection improves, thereby increasing contrast.

18

A-True; patient penetration requirements are similar;

B-False; fluoroscopy mA values are in the range 1 to 5 mA whereas in radiography, these are typically 100 mA;

C-False; radiographic exposure times are typically tens or hundreds of milliseconds whereas fluoroscopy exposure times are seconds or minutes;

D-True;

E-True; grid ratios of about 10:1 are used for both fluoroscopy and radiography.

19

E.

There is no exposure time in fluoroscopy since the x-ray beam is on all the time.

20

E.

None of the above; variation in input x ray photons (quantum mottle) is the dominant noise source in fluoroscopy.

21.

A-ii;

B-iv; screen film exposure for a 400 speed system is about 0.3 mR;

C-iii; photo spot film needs about 1/3 dose of spot film exposures

D-i; there is no exposure during last image hold.

22.

A-True;

B-True;

C-False; analog-to-digital converters are used;

D-False; limiting resolution is about 2 line pairs per mm for 1000-line TV system;

E-True; DSA systems require fast and high capacity disk drives up to about 50 MBytes.

23

D.

The digitization matrix is the primary determinant of DSA spatial resolution performance (typical values are 5122 or 10242

24.

C-True; 7.5 vs. 30 frames per second;

D-False; by subtracting frames with and without contrast, vessel visibility increases significantly.

25

A-False; acquisition frame rate is more likely to be reduced because the computer will be unable to cope with the extra data being acquired;

B-True; there will be a fourfold Increase in the digitization rate;

C-True; A fourfold increase in data if the frame rate remains constant;

D-True; there is more data to process;

E-False; the hard copy filming time is not dependent on DSA matrix size.