ch 15,17 & 18

Question 1

what is scatter

Answer 1

photons reaching the IR not part of the useful beam, impair image quality

Question 2

what interaction causes scatter

Answer 2

compton interaction

Question 3

what affect does scatter have on a radiograph

Answer 3

increases density , by increasing fog

Question 4

what are the factors affecting scatter

Answer 4

kilovoltage & irradiated material

Question 5

how does kVp affect scatter

Answer 5

as kVp increases scatter increases

Question 6

how does the irradiated material affect scatter

Answer 6

as the volume increases the scatter increases

Question 7

how do beam restrictors affect scatter

Answer 7

decrease scatter, as restrictions increase scatter decreases

Question 8

name the types of beam restrictors

Answer 8

collimator, aperture diaphragms , lead impregnated rubber, cones/cylinders

Question 9

inherent filtration is

Answer 9

built into the tube

Question 10

what is the most common beam restrictor

Answer 10

collimator

Question 11

what is PBL?

Answer 11

positive beam collimation device - automatic collimation of the beam size

Question 12

what film size has the most scatter, why?

Answer 12

14 by 17 - increased volume

Question 13

the bluriness around the edge of an image is called

Answer 13

penumbra

Question 14

the difference between collimation & shuttering

Answer 14

collimation is a pre exposure reduction of beam, shuttering is post exposure

Question 15

what is the type of beam limiting device that gets attached to the collimator tube housing, that has an opening cut in the middle

Answer 15

aperture diaphragms

Question 16

what is a blocker used for

Answer 16

reduce scatter from patient reaching the IR

Question 17

what is a mask used for

Answer 17

cut as a specific shape

Question 18

who invented the grid

Answer 18

gustav bucky

Question 19

who invented the bucky

Answer 19

hollis potter

Question 20

what color is photoelectric on an IR

Answer 20

white

Question 21

what is the purpose of a grid

Answer 21

improves contrast of image, absorbs scatter before reaching IR

Question 22

what materials are grids made out of

Answer 22

lead, interspace made out of radiolucent material (plastic)

Question 23

define grid ratio

Answer 23

the height of the lead strips to the distance between the strips

Question 24

define grid frequency

Answer 24

the number of grid lines per inch or cm

Question 25

what is the formula for figuring grid ratio

Answer 25

grid ratio = h / d height over distance

Question 26

when should a grid be utilized

Answer 26

imaging anatomy over 10 cm or above 60 kVp

Question 27

high grid ratios allow ___ scatter to pass thru to the IR

Answer 27

less

Question 28

lead strips are thicker in ___ frequency grids

Answer 28

low

Question 29

why is a high frequency grid used for digital

Answer 29

lead strips are thinner

Question 30

name the two types of grid patterns

Answer 30

linear & criss crossed

Question 31

name the three types of grids

Answer 31

parallel , focused, long or short dimension

Question 32

what grid type is used the most

Answer 32

focused

Question 33

what grid type is the easiest to use?

Answer 33

focused

Question 34

what grid type is the hardest to use

Answer 34

parallel

Question 35

what is a convergence line

Answer 35

the point where grid lines meet

Question 36

how much radiation does it take to make an exposure

Answer 36

1mR/ hr

Question 37

what does focal range mean

Answer 37

distance at which the divergence of the beam & grid lines will match

Question 38

types of grid movements

Answer 38

reciprocating & oscillating

Question 39

what is meant by grid selectively? the formula?

Answer 39

% of primary radiation transmitted over————————— % of scatter radiation transmitted

Question 40

what is meant by contrast improvement ability ? formula ?

Answer 40

how good the grid is at improving contrast k = radiographic contrast with the grid over ———————— radiographic contrast without the grid

Question 41

what is the alternate to using a grid

Answer 41

restrict beam size air gap technique - increase OID

Question 42

main purpose of filtration

Answer 42

reduce patient dose by taking out low energy photons

Question 43

filtration works because

Answer 43

it removes soft x rays (low energy photons)

Question 44

filtration is measured in

Answer 44

HVL - half value layer

Question 45

material for filtration

Answer 45

aluminum & copper

Question 46

2 types of filtration

Answer 46

added & inherent

Question 47

they type of filtration the tech adds

Answer 47

added filtration

Question 48

total filtration is

Answer 48

sum of added and inherent filtration

Question 49

when above 70 kv you have to have

Answer 49

2.5 mm of aluminum equivalent

Question 50

largest producer of scatter

Answer 50

the patient

Question 51

what affects detail the most

Answer 51

OID ( magnification )

Question 52

photoelectric interaction adds to

Answer 52

the patient dose, passes through the body easier

Question 53

as scatter increases , absorption

Answer 53

decreases