Unit 4

Question 1

Define attenuation

Answer 1

Reduction in total number of X-ray photons after passing through matter

Question 2

Amount of attention is determined by:

Answer 2

Amount of material irradiated

Type of material irradiated (density of part and atomic number)

Question 3

Lowest attenuation to highest:

Answer 3

Air
fat
Muscle
Bone

Question 4

Subject density

Answer 4

Image receptor exposure is altered by changes in the amount or type of tissue in the patient
Atomic number and thickness

Question 5

Subject contrast

Answer 5

Image contrast is affected by the degree of differential absorption resulting from differing absorption characteristics of body tissues

Question 6

Abdomen has what contrast

Answer 6

Low

Question 7

Chest has what contrast

Answer 7

High

Question 8

Subject detail

Answer 8

Recorded detail is dependent on a structured position within the body and placement in relationship to film
Close to IR to reduce penumbra

Question 9

Subject distortion

Answer 9

May not be accurately represented on a radiograph

Question 10

Additive

Answer 10

Increase attenuation

5-15% increase in kV

Question 11

Destructive

Answer 11

Decrease attenuation

25-50% decrease in mAs

Question 12

Tumors

Answer 12

Additive

Question 13

Pneumonia

Answer 13

Additive

Question 14

Ascites

Answer 14

Additive

Question 15

Anorexia nervosa

Answer 15

Destructive

Question 16

Emphysema

Answer 16

Destructive

Question 17

Pneumothorax

Answer 17

Destructive

Question 18

Osteoporosis

Answer 18

Destructive

Question 19

Star pattern

Answer 19

Metal template with star pattern

Easy to use, most practical, requires low exposure

Question 20

Wisconsin focal spot test tool

Answer 20

Metal template with vertical and horizontal line pairs

Good for ongoing QC check to see if any drastic change in size

Question 21

Pinhole camera

Answer 21

Pin sized hole in metal plate

Difficult to use and requires excessive exposure

Question 22

Slit camera

Answer 22

Standard tool used to measure effective spot size

Slit cut in metal plate

Question 23

Advantages of magnification radiography

Answer 23

Scatter clean up- no g rid

High kV utilization

Question 24

Disadvantages of magnification radiography

Answer 24

Increased patient dose
Decreased FOV
Decreased resolution

Question 25

For best consistency in radiographs

Answer 25

Measurement of part | Technique chart

Question 26

Establishing a technique chart

Answer 26

``` Phantom images Select optimal phantom image (what radiologist will read) Extrapolate technique chart Phantom testing for different sized pts. Clinical trials Clinical fine tuning Ongoing fine tuning ```

Question 27

Advantages of Fixed kV

Answer 27

``` Decrease patient dose Uniform contrast Wider latitude Low tube heating Extended tube life Decrease time/ less motion ```

Question 28

Disadvantages of fixed kV

Answer 28

Use high kV low contrast more scatter | Small increments in mAs may not be possible

Question 29

Variable kV systems

Answer 29

KV varies according to body part thickness | mAs value specified for each body part

Question 30

Advantages of variable kV

Answer 30

Permits small increments changes | Higher contrast images less scatter

Question 31

Disadvantages of variable kV

Answer 31

Varying contrast High patient dose Increased tube wear

Question 32

Problems with phototiming

Answer 32

``` Poor positioning Pathology Combination Minimum response time Back up time must be set ```