Physics 6 Questions

1. Match the following components of an image intensifier (II) system with their functions.


(A) Anode

(B) Input phosphor

(C) Photocathode

(D) Output screen


(i) Absorbs light and emits electrons

(ii) Absorbs x-rays and emits light

iii) Absorbs electrons and emits light

(iv) Provides a positive voltage




2. The II input phosphor is made of


(A) NaI

(B) ZnCdS


(D) CsI

(E) none of the above








3. The II output phosphor is made of


(A) Nal

(B) ZnCdS


(D) CsI

(E) none of the above









4. The brightness gain of an II tube does NOT depend on the


(A) patient dose

(B) efficiency of the photocathode

(C) voltage across the II tube

(D) ratio of input to output screen sizes

(E) output phosphor conversion efficiency









5. Typical values for modern IIs do NOT include


(A) minification gains of 100

(B) flux gains of 50

(C) contrast ratios of 2:1

(D) brightness gains of 5000

(E)  spatial resolutions of 5 line pairs per mm









6. Match the following operational parameters for II systems with the appropriate values.


(A) Accelerating voltage

(B) Entrance skin exposure rate

(C) Vignetting

(D) High contrast resolution


(i) 5 line pairs per mm

(ii) 20% loss of light intensity at field edges

(iii) 3 R/min

(iv) 25kV




7. If the entrance skin exposure (ESE) rate of an II operated in the 30-cm mode is 1 R/min the ESE rate in the 15cm mode would be


(A)  l/4 R/min

(B) 1/2 R/min

(C) unchanged

(D) 2R/min

(E) 4R/min









8. If a 25-cm diameter II (2.5-cm output diameter) has a brightness gain of 5,000, then the flux gain is approximately


(A) 500

(B) 50

(C) 5

(D) unchanged

(E) cannot be determined








9. Changing the magnification mode of an image intensifier from 30 cm to 15 cm in fluoroscopy will normally increase


(A) entrance skin exposure rate

(B) distortion

(C) vignetting

(D) image brightness










10. The reason for interlacing two fields to form one frame in a conventional TV system is to reduce the


(A) patient dose

(B) motion artifacts

(C) input phosphor lag

(D) quantum mottle

(E) flicker








11. Vertical resolution of a standard North American TV is


(A) > horizontal resolution

(B) > European TV

(C)  0.7 x 30 frames per second

(D) 0.7 x 60 fields per second

(E) 0.7 x 262.5 line pairs









12. The horizontal resolution of a TV system is primarily determined by the


(A) image brightness

(B) bandwidth

(C) number of TV lines

(D) radiation exposure level

(E) focal spot size








13. The vertical resolution of a TV system is primarily determined by the


(A) image brightness

(B) bandwidth

(C) number of TV lines

(D) radiation exposure level

(F) focal spot size









14. In 35-mm cardiac cine, for a constant film density, patient entrance skin exposure is reduced by increasing the


(A) acquisition frame rate

(B) kV

(C) mA

(D) grid ratio

(E) focal spot size








15. Match the resolution with the viewing modes assuming the same image intensifier is used.


(A) 525-line TV

(B) Video cassette recorder

(C) 1025-lineTV

(D) II output phosphor image


(i)  1.0 lp/mm

(ii)  1.2 lp/mm

(iii)  2.5 1p/mm

(iv)  5.0  lp/mm




16. The limiting spatial resolution in fluoroscopy can be improved by increasing the


(A) grid ratio

(B) II input size

(C) radiation dose level

(D) kV

(E) none of the above









17. Low contrast detectability in fluoroscopy images can be improved by increasing the


(A) focal spot size

(B) kVp

(C) x-ray beam filtration

(D)) grid ratio

(E) fluoroscopy time








18. True (T) or False (F). Compared with radiographic film/screen exposures, fluoroscopy uses similar


(A)  kVp

(B) mA

(C) exposure times

(D) added x-ray beam filtration

(E) grids









19. For manual technique fluoroscopy, image brightness at the output phosphor of an image intensifier is likely to be affected by all of the following parameters EXCEPT


(A) kVp

(B) mA

(C) patient thickness

(D) grid ratio

(E) exposure time







20. The major contributor to noise in a fluoroscopic image is variations in the


(A) input phosphor thickness

(B) accelerating tube voltage

(C) output phosphor thickness

(D) display screen brightness

(E) none of the above









21. Match the following fluoroscopy imaging procedures with the II input exposure per single frame.


(A) Conventional fluoroscopy

(B) Screen/film imaging

(C) Photospot film imaging

(D) Last image hold viewing


(i)  0 μR

(ii) 2 μR

(iii) l00 μR

(iv) 300  μR




22. True (T) or False (F). In digital subtraction angiography (DSA)


(A) image intensifiers are used to create the images

(B) low noise TV cameras should be used

(C) a digital-to-analog converter samples the video signal

(D)  spatial resolution is about 5 to 10 line pairs per mm

(E)   image archival on optical disk is possible









23. The most important component affecting spatial resolution in DSA is the


(A) focal spot size

(B) II input phosphor thickness

(C) II output phosphor thickness

(D) digitization matrix

(E)  computer CPU









24. True (T) or False (F). When compared with cine angiography DSA


(A) uses a lower dose per frame

(B) has a lower spatial resolution

(C) uses lower frame rates

(D)  has inferior detectability of contrast filled vessels









25. True (T) or False (F). Changing DSA matrix alone from 512 x 512 to 1024 x 1024 requires an increased


(A)  acquisition frame rate

(B)  analog-to-digital converter performance

(C) data storage requirement

(D) image processing time

(E)  hard copy film processing time