fluoro facts

Question 1

Minimum SOD (source to object distance)

Answer 1

30-38cm or 12 on stationary fluoro

Question 2

standard OID (object image distance)

Answer 2

100cm/40” (results in 1.1 magnification) but in general place object/person as close to the image receptor as possible

Question 3

Normal KVP for fluoro

Answer 3

75-125kVp

Question 4

increased kvp leads to ____ dose and ___ contrast

Answer 4

decreased, decreased. KVP and dose are inversely proportional, KVP and contrast are also inversely proportional

Question 5

Automatic Brightness control (ABC)

Answer 5

maintains a constant image (brightness/contrast) even with variations in patient attenuation by regulating mAs and kVp

Question 6

automatic exposure control (AEC)

Answer 6

adjust the kVp, mAs, or exposure time in order to obtain an image of diagnostic quality by measuring dose

Question 7

Quantum mottle/noise

Answer 7

○ Number of XRs per area per unit time is random - thus image is random b/c it contains quantum uncertainty AKA mottle AKA noise
○ Basically artifact caused by too few XRs reaching the detector or too much noise (high SNR)
○ Appears as grainy or textured pattern

Question 8

to cut noise in half, what do you have to do with the number of XRs?

Answer 8

increase XRs by 4. More XRs decrease noise

Question 9

Signal to Noise Ratio (SNR)

Answer 9

-primary determinant of image quality referring to signal (useful info) to noise (crap such as scatter, background electrical interference)
■ High SNR - better image quality and generally higher radiation dose

Question 10

Magnification

Answer 10

Ratio of the image size to object size in an XR projection from a point source

Question 11

bit depth

Answer 11

Contrast resolution, which is affected by the number of gray levels a pixel has. indicates the number of possibilities for defining a grayscale value, from black to white. it is the exponent value ( for example 2^8 is “8 bit depth”= 256)

Question 12

Bit depth used in angiography

Answer 12

12 bit depth (2^12)

Question 13

normal measurement of background radiation

Answer 13

100-150mR/year

Question 14

how much radiation is a CXR (in mR)

Answer 14

15-20mR

Question 15

how much radiation is a KUB? (in mR)

Answer 15

200-400mR

Question 16

how much radiation is a CT

Answer 16

2000-8000mR

Question 17

how much radiation is fluoro mR/min on the table)?

Answer 17

1000-10,000 mR/min on the table

Question 18

1 gray (Gy) = ___ rads

Answer 18

100

Question 19

Maximum Annual Occupational Dose (Sv) for whole body

Answer 19

0.05 Sv/year

Question 20

Maximum Annual Occupational Dose for eyes (Sv)

Answer 20

0.15 Sv / yr

Question 21

Exposure required to produce cataract

Answer 21

2.0 Sv

Question 22

Maximum Annual Occupational Dose for skin (Sv)

Answer 22

0.5 Sv / yr

Question 23

High Radiation Area

Answer 23

place where a person could be exposed to a 1 mSv/hr @ 30 cm from source

Question 24

Radiation Area

Answer 24

place where a person could be exposed to 0.05 mSv/hr @ 30 cm from source

Question 25

an unrestricted area will allow how much radiation

Answer 25

can be exposed to 0.02 mSv/hr

Question 26

Immediate reporting required if total effective dose is > ___?

Answer 26

>25rem

Question 27

Immediate reporting required if eye dose is > ___?

Answer 27

>75 rem

Question 28

Immediate reporting required if skin dose is > ___?

Answer 28

>250 rem

Question 29

24 hour reporting required if total effective dose is > ___?

Answer 29

5 rem

Question 30

24 hour reporting required if eye dose is > ___?

Answer 30

15 rem

Question 31

24 hour reporting required if skin dose is > ___?

Answer 31

>50 rem

Question 32

Kell factor

Answer 32

ratio between the vertical resolution of a television monitor and the number of horizontal scan lines

Question 33

genetically significant dose

Answer 33

Number of future children X-ray examination rate Average gonadal dose per examination