fluoroscopy

Question 1

what is fluoroscopy used for?

Answer 1

to visualise motion, x-ray in real time

Question 2

continuous _ _ exposure is needed for fluoroscopy

Answer 2

continuous low dose exposure is needed for fluoroscopy

Question 3

what is required due to the use of low dose exposure in fluoroscopy?

Answer 3

an image intensifier

Question 4

what is the goal of the image intensifier

Answer 4

to brighten the image

Question 5

name three components of the image intensifier

Answer 5

input phosphor, photocathode, output phosphor

Question 6

what does the photocathode do?

Answer 6

converts light to photoelectrons

Question 7

what is inputted into the input phosphor?

Answer 7

x-rays

Question 8

what % of x-ray input is absorbed by the input phosphor and why?

Answer 8

60% of incoming x-rays are absorbed by the input phosphor, this is due to the k-edge effect

Question 9

what happens to the photoelectrons after the photocathode?

Answer 9

they are accelerated across the tube by a high voltage (25kV) towards the output phosphor

Question 10

the image produced by fluoroscopy is
1.
2.
3.

Answer 10

the image produced by fluoroscopy is:
1. inverted
2. reversed
3. minified

Question 11

where is the lowest efficiency in the II?

Answer 11

At the input phosphor

Question 12

what is the intensification factor

Answer 12

the intensification factor is a measure of the increase in light output compared with the light produced at the input phosphor

Question 13

what two factors influence the intensification factor?

Answer 13

the minification gain and the flux gain

Question 14

flux gain formula?

Answer 14

electrons from output phosphor

/
#electrons from input phosphor

Question 15

minification gain formula?

Answer 15

diameter of the input phosphor
/
diameter of the output phosphor

Question 16

what is the reasoning behind the pincushion effect?

Answer 16

distortion of the image due to the divergence of the peripheral electrons at the output phosphor, leading to unequal magnification

Question 17

what is vignetting?

Answer 17

this is where the centre of the image is brighter than the peripheral, also due to diverging peripheral electrons

Question 18

what detects the light from the output phosphor?

Answer 18

charge coupled device (CCD) detects the light from the output phosphor

Question 19

what does modern fluoroscopy use instead of the image intensifier

Answer 19

modern fluoro units use a flat panel image receptor

Question 20

what does magnification improve in II fluoroscopy, but not in digital fluroscopy?

Answer 20

magnification improves spatial resolution in older fluoroscopy units, but does not improve spatial resolution in digital fluoroscopy.

Question 21

advantages of digital fluoroscopy?

Answer 21

no distortion, unaffected by magnetic fields, wide dynamic range, improved contrast.