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Flashcards in Midterm 2 - Memorize Deck (27)
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1

How do you double density (2)

Double mAs
Increase kVp 15%

2

Double mAs and you

double density

3

Increase SID and you

reduce beam intensity

4

Increase kVp 15% and you

Double image density; lower contrast

5

Minimize scatter (5)

Grid
Air gap technique = to 8:1 grid
Minimize volume of tissue (collimating)
Decrease kVp
Decrease mAs

6

Air gap technique equal to what kind of grid

8:1

7

Things that increase scatter (3):

- more tissue volume
- more kVp
- more mAs

8

Fog is caused by (6 - LA SHOT)

- light: safelight exposure, light leaks in dark room
- accidental radiation exposure
- scatter
- high film storage temp or pressure
- old film
- TTT: too much/not enough time, temp, titration or exposure to darkroom chemical fumes

9

Increased film OR screen speed causes ___ and mean what about mAs?

More density

So less mAs needed to create density

10

Usual value for gross fog index

0.15 to 0.20

11

Faster films have higher/lower gross fog index

Higher

Gross fog index is Base plus Fog. Unexposed film will be 0.15-0.20. Faster films will be closer to 0.20 while slower films will be closer to 0.15

12

The longer the toe of H&D curve, the more/less sensitive to fog the film is

Less

13

Speed index is the step wedge strip that has the closest optical density to

1.0

14

Contrast index step should be _____ for films used for skeletal images

1.4-1.7

15

Gross fog index is

(Film) Base plus Fog

16

Shoulder of the curve represents

D-max

Max optical density the film will achieve

17

Body of the curve shows what? What does a high vertical rise vs a less steep slope mean?

Latitude

high slope: short latitude and high contrast film

LLL: Low slope: Long latitude and Low contrast film

18

The H&D curve plots what and what?

Optical density (vertical)

Log relative exposure (horizontal)

19

Changes in SID from 40 to 56” you want to multiply original mAs by

2

20

Changes in SID from 40 to 80” you want to multiply original mAs by

4

21

Changes in SID from 40 to 72” you want to multiply original mAs by

3

22

mAs rule (equation)

mAs1 D1^2
———=————
mAs2 D2^2

23

Inverse square law (equation)

I1 D2^2
——=———
12 D1^2

24

What increases magnification (2)

Increased OID
Decreased SID

25

Image sharpness is affected by (3)

FSS (focal spot size)
OID
SID

26

Under-replenishment of automatic developer titration results in (2)

Loss of contrast
Loss of film density

27

Densitometer reports on a scale of 0 to 4. O means what? 4 means what?

0 means 0% transmission through film

4 means 100% light transmission through film