Exposure Variables

Question 1

what 3 things affect beam quantity & how

Answer 1

Intensity - energy/sec
Heating up the filament - increase mA = increase heat
Time - length of exposure

Question 2

mA and time have a _________ relationship

Answer 2

inverse

Question 3

What are the advantages to decreased time

Answer 3

Decrease motion artifacts
Decrease personnel exposure
Higher mA better for thicker body parts

Question 4

Which type of wavelength penetrates better

Answer 4

Shorter

Question 5

What is Sante’s rule

Answer 5

(2x thickness[cm]) + 40 = kVp
Starting point to figure out kVp

Question 7

Kvp and mAs have a ________ relationship

Answer 7

Inverse

Question 8

What typically happens when you decrease mAs but increase kVp

Answer 8

Same exposure

Question 9

What is SID

Answer 9

Source (x-ray tube) - image (film) distance

Question 10

What happens to intensity if you increase distance

Answer 10

Decreases

Question 11

Why is it important that SID should stay the same

Answer 11

It gets rid of the chance of distance affecting the diagnostic quality of an image

Question 12

What factors affect image quality (3)

Answer 12

Radiographic density
Radiographic contrast
Geometric factors

Question 13

What is density in regards to xrays

Answer 13

Degree of blackness on the film. Look at a spot where there is no object. Shows how many xrays are reaching the film

Question 14

What is contrast in regards to xrays

Answer 14

What gets through the subject to the film. Degrees of grey on film

Question 15

what geometric factors affect film quality (5)

Answer 15

Focal spot size
Motion
SID
Object to film distance
Distortion

Question 16

What does more distance create in regards to object to film distance

Answer 16

More distance creates magnification and blurry edges

Question 17

What will increased tissue density do to film density

Answer 17

Increases xrays absorbed and decreases film density

Question 18

What are the 5 basic densities

Answer 18

Air
Fat
Water
Bone
Metal

Question 19

What does contrast show in xrays

Answer 19

Film density between adjacent structures

Question 20

What does low contrast mean

Answer 20

Long scale, many more shades of grey. High kVp

Question 21

What does high contrast mean

Answer 21

Short scale. Mostly black & white. Low kVp exposure

Question 22

if a film has low kVp exposure what type of contrast will it have

Answer 22

high contrast, short scale

Question 23

If a film has high kVp what type of contrast will it have

Answer 23

Low contrast, long scale

Question 24

If you want an x-ray of a bone what type of contrast should you have

Answer 24

High contrast
Low kVp and high mas

Question 25

What factor affects contrast

Answer 25

kvp

Question 26

If you want to take an x-ray of the abdomen what type of contrast should you have

Answer 26

Low contrast to see variations in all of the organs

Question 27

What is the primary factor that affects density

Answer 27

mAs - affects x-ray quantity

Question 28

T/F kVp only affects contrast

Answer 28

FALSE. Slightly affects density as well

Question 29

What can scatter xrays cause

Answer 29

Unwanted film exposure & "film fog"

Question 30

how can you minimize scatter

Answer 30

Beam limiting Filters Grids Decrease air gap

Question 31

Where are filters on an x-ray machine

Answer 31

Between tube and beam limiters

Question 32

How do grids work on an x-ray machine

Answer 32

Built into the table. Alternating lead strips absorb scatter. Transulscent spacers let wanted xrays through

Question 33

Since grids can absorb some good photons, how can you compensate?

Answer 33

Increase mAs and increase # of photons

Question 34

What types of grids are there (4)

Answer 34

Parallel Focused Linear Crossed

Question 35

if an object moves closer to the source, what happens to the image

Answer 35

Magnification

Question 36

What happens if the beam is not perpendicular to the receptor

Answer 36

elongation

Question 38

What will happen if the subject is not parallel to the film

Answer 38

fore shortening