fluoroscopy

Question 1

photospot matrix size

Answer 1

1024x1024, 2 bytes/pixel, 2 MB

Question 2

fluoro resolution

Answer 2

1 lp/mm

Question 3

photospot resolution

Answer 3

2 lp/mm

Question 4

number of photons/mm2

Answer 4

1000 photons/mm2

Question 5

usual fluoro skin dose

Answer 5

<500 mGy

Question 6

max allowed Kair in standard fluoro

Answer 6

100 mGy/min
no limit for photospot or cine
non-standard fluoro can have more

Question 7

fluoro mode vs % of II exposed

Answer 7

normal, 100%
Mag I, 50 % (2X peak skin dose because ABC maintains brighteness at output)
Mag II, 25%, 4X peak skin dose

Question 8

dose from fluoro vs photospot images

Answer 8

1 min of fluoro (10 mGy/min) deliverrs same patient dose as 10 photosphot images (1 mGy/image)

Question 9

AEC vs ABC

Answer 9

AEC keeps Kair at image receptor constant irrespective of xray beam area
ABC changes Kair only when electronic magnification is changed

Question 10

does pulsed fluoro reduce patient dose?

Answer 10

only if < 30 fps

Question 11

what is pulsed fluoro

Answer 11

tube current is on for a short perios but increased to maintain same mAs for each frame as for continuous fluoro

Question 12

brightness gain

Answer 12

flux gain X minification gaim
~ 5000

Question 13

TV display

Answer 13

30 fps

Question 14

minification gain

Answer 14

area of input phosphor/output phosphor

Question 15

typical fluoro kerma area product

Answer 15

20 Gycm2

Question 16

what does output phosphor do

Answer 16

absorbs electrons and emits light photons

Question 17

effective dose fluoro exam

Answer 17

4 mSv

Question 18

focal spot size fluoro

Answer 18

0.6 mm
1.2 mm for photospot imaging

Question 19

what does photocathode do?

Answer 19

absorbs light photons from input phosphor and emits electrons

Question 20

does switching from 30fps to 15 fps reduce dose?

Answer 20

-only by 35% because 15 fps uses higher dose per frame

Question 21

mA and power for fluoro

Answer 21

< 0.5 kW
3 mA

Question 22

what does lens do?

Answer 22

accelerates electrons and focuses them to output phosphor

Question 23

what is temporal filtering

Answer 23

frame averaging

Question 24

is KAP affected by magnification?

Answer 24

no because Kair increases due to ABC and area is reduced (but peak skin dose affected)

Question 25

what does input phosphor do?

Answer 25

absorbs xray and remits as photons

Question 26

veiling glare

Answer 26

light scattering in output phosphor

Question 27

fluoro kV

Answer 27

80 kV

Question 28

resolution of II

Answer 28

5 lp/mm
2lp/mm with TV

Question 29

tube current for photospot image

Answer 29

several hundred mA

Question 30

what happens to entrance Kair if patient thickness increases by 3 cm?

Answer 30

it doubles

Question 31

order of parts in II

Answer 31

input phosphor- photocathode- lens- output phosphor

Question 32

fluoro storage requires for 1 frame

Answer 32

0.5 MB

Question 33

Kair at image receptor

Answer 33

0.03 uGy/frame
3 uGy/image for photospot

Question 34

why is input phosphor curved?

Answer 34

lets you make it thin with minimizes absorption of incident xrays

Question 35

flux gain

Answer 35

light at input/photons at input
~50

Question 36

halving input FOV for II vs flat panel detector

Answer 36

-would quadruple Kair for II but only double it for FPD because FPD would use binning to reduce mottle (also reduces resolution)

Question 37

response of flat panel detectors

Answer 37

linear

Question 38

how to change resolution in fluoro

Answer 38

play with II FOV

Question 39

fluoro imaging parameters

Answer 39

80-100 kVp, 3 mA

Question 40

fluoro power rating

Answer 40

0.5 kW

Question 41

3 levels of dose for fluoro

Answer 41

50 mGy/min, 100 mGy/min, 150 mGy/min

or

10R/min in normal and 20R/min in high dose or detail mode