chapter 20-21

Question 1

what are the causes of scatter radiation

Answer 1

• high kVp
• large field size
• large part thickness

Question 2

difference between scatter and blur

Answer 2

• scatter is completely random and blue is geometrically predictable

Question 3

what does scatter affect

Answer 3

image visibility:
- exposure
- subject contrast
- noise

Question 4

function of the grid

Answer 4

absorbs scatter radiation that has already been produced in patients body before it reaches the IR

Question 5

what eliminates grid lines

Answer 5

potter-bucky diaphragm

Question 6

what is the grid ratio

Answer 6

ratio of the height to the width of the interspaces between the lead strips

Question 7

field size has a greater impact upon…

Answer 7

scatter radiation

Question 8

what are the indications for grid use

Answer 8

• thickness of soft tissue
• size of the field
• kvp used

Question 9

what is the ratio of primary radiation transmitted through the grid to scatter radiation transmitted through the grid

Answer 9

selectivity

Question 10

body parts thicker than ____ require a grid

Answer 10

10 cm

Question 11

what is the grid conversion factor formula

Answer 11

mAs1/ mAs2 = GCF1/GCF2

Question 12

what do grids affect

Answer 12

visibility functions

Question 13

grid lines can be minimized using which 3 things

Answer 13

• proper distance
• proper alignment
• potter-bucky diaphragm

Question 14

what is canting

Answer 14

the tilting of lead strips

Question 15

what is the distance from the lead strips to focal spot

Answer 15

grid radius

Question 16

which grid involves the lead strips to be tilted as they move away from the center of the grid

Answer 16

focused grids

Question 17

which grid has no tilting

Answer 17

parallel

Question 18

the grid radius for a parallel grid is…

Answer 18

infinity

Question 19

what causes an asymmetrical loss of exposure

Answer 19

tilting the grid, misalignment, angling of the beam

Question 20

what is the anode bevel

Answer 20

angle of the target surface to the anode

Question 21

anode bevel affects…

Answer 21

• line focus principle
• anode heel effect

Question 22

what is the line focus principle controlled by

Answer 22

• width of electron beam to filament
• angle of anode bevel

Question 23

the line focus principle makes it possible to achieve a…

Answer 23

small effective focal spot and maximum sharpness

Question 24

what is the anode bevel of standard x-ray tubes

Answer 24

15-17 degrees

Question 25

what is the anode bevel for special procedures such as angiography

Answer 25

7-10 degrees

Question 26

where are the x-rays being produced

Answer 26

actual focus spot

Question 27

which side is the anode on

Answer 27

left side

Question 28

does the cathode or anode receive more radiation

Answer 28

cathode

Question 29

a variation in the x-ray intensity along the longitudinal tube axis

Answer 29

anode heel effect

Question 30

the heel effect is worsened with…

Answer 30

• steeper bevel angles
• longer field size
• large focal spots
• shorter SIDs

Question 31

it is always best to place the ____ end of anatomy towards the anode

Answer 31

thinnest

Question 32

what is the only image quality affected by focal spot size

Answer 32

spatial resolution

Question 33

focal spot is _____ proportional to spatial resolution

Answer 33

inversely

Question 34

focal spot is _____ proportional to penumbra

Answer 34

directly

Question 35

when the focal spot is doubled the penumbra is _____

Answer 35

doubled

Question 36

focal spot does not affect

Answer 36

magnification

Question 37

what kind of factor is the focal spot

Answer 37

geometrical factor

Question 38

image magnification is only affected by

Answer 38

distance