chapter 18-19

Question 1

what are the purposes of field size limitation

Answer 1

• to minimize radiation exposure to patient
• preserve subject contrast in the remnant x-ray beam

Question 2

who discovered the first x-ray beam filter

Answer 2

william rollins

Question 3

what is the most effective device for providing a sharp field border which force the x-ray beam to effectively pass through

Answer 3

collimator

Question 4

what is produced anywhere outside of the focal spot when electrons scatter and the strike the glass envelop

Answer 4

off focus radiation

Question 5

off focus radiation is produced in ______ of the xray tube

Answer 5

any portion

Question 6

another name for positive beam limitation

Answer 6

automatic collimators

Question 7

when can PBL be overridden

Answer 7

when the field needs to be smaller than the IR

Question 8

the ____ should always be fully included within the xray field

Answer 8

the anatomy of interest

Question 9

clipping the anatomy can result in…

Answer 9

repeating exposures, doubling patient exposure

Question 10

for anatomy smaller than the IR allow at least ____ of light beyond each edge

Answer 10

1/2 inch or 1 cm

Question 11

the amount of scatter radiation is controlled by

Answer 11

-size of the patient
- size of the x-ray field

Question 12

subject contrast is changed when the ratios when between primary rays, photoelectric interactions and compton scatter interactions are…

Answer 12

altered

Question 13

good subject contrast within the patient is dependent upon

Answer 13

proportions of different interactions within the patient relative to each other

Question 14

how does smaller collimation affect subject contrast

Answer 14

subject contrast is improved

Question 15

what does field size affect

Answer 15

visibility functions of the image

Question 16

what is the four cm rule

Answer 16

for ever 4 cm change in part thickness, adjust the mAs by a factor of 2 or kVp by 15%

Question 17

what is the minimum change rule

Answer 17

a 35% increase in the mAs, or 15% decrease in kVp to bring any significant alteration in final exposure

Question 18

5 types of body habitus

Answer 18

• sthenic
• hyposthenic
• asthenic
• hyperstenic
• large muscular

Question 19

who should you reduce kVp for

Answer 19

pediatric or geriatric patients

Question 20

what are the types of tissues used on radiography

Answer 20

• metal
• bone
• soft tissue
• fat
• gas

Question 21

additive diseases

Answer 21

increase fluid, bone, or metal content within tissue

Question 22

why does positive contrast absorb more radiation

Answer 22

appears radiopaque

Question 23

rule of thumb for additive diseases

Answer 23

increase overall technique by 50%

Question 24

for a pathological condition to require an adjustment in technique it must alter one of the five techniques which are…

Answer 24

• air
• fat
• fluid
• bone
• metal

Question 25

destructive diseases

Answer 25

increases in air or fat, or decreases normal fluid or bone

Question 26

rule of thumb for destructive diseases

Answer 26

decrease mAs by 35% or kVp by 8%

Question 27

acromegaly: additive or destructive

Answer 27

additive

Question 28

carcinomas: additive or destructive

Answer 28

additive

Question 29

emphysema: additive or destructive

Answer 29

destructive

Question 30

Osteoarthritis and osteochondroma: additive or destructive

Answer 30

additive

Question 31

osteomyelitis: additive or destructive

Answer 31

destructive

Question 32

pneumothorax: additive or destructive

Answer 32

destructive

Question 33

what are better visualized using the soft tissue technique

Answer 33

slivers of wood or glass, swallowed bones

Question 34

rule of thumb for soft tissue technique

Answer 34

reduce kVp by 20%