ch 26-27-28-29physics

Question 1

which of the 2 image properties determines if the IR was sufficiently exposed?

Answer 1

density

Question 2

structural details are made up of ________ and _______.

Answer 2

density and contrast

Question 3

density is considered an ______ _______ _______.

Answer 3

image quality factor

Question 4

are brightness and density interchangeable?

Answer 4

no

Question 5

a monitor control function that can change light and dark on an image on the display monitor

Answer 5

brightness

Question 6

with film and digital radiography the key to a visible image is….

Answer 6

having the correct IR exposure

Question 7

window level controls

Answer 7

brightness

Question 8

when the IR receives too many photons and records to much information it is called

Answer 8

overexposure

Question 9

when the IR did not receive enough information it is considered

Answer 9

underexposed

Question 10

what is the controlling factor of density for film and digital radiography?

Answer 10

mAs

Question 11

with film we need to adjust mAs _____% to see a visible change in density

Answer 11

30

Question 12

why must we monitor density with the Ei number?

Answer 12

because regardless of the exposure the computer system will attempt to rescale the histogram so the images acceptable to the eyes

Question 13

what is the general rule of thumb for density

Answer 13

make changes in increments of doubles or halves

Question 14

what is the primary influencing factor of density?

Answer 14

mAs

Question 15

in what two ways does kv alter the intensity of the beam that reaches the IR?

Answer 15

controls the energy of the e- that strike the anode

controls the average energy of the X Ray photons produced at the anode target

Question 16

a change in kv alters the intensity of the beam when mAs and other factors _____ ______ ______.

Answer 16

stay the same

Question 17

what is the minimum change in kv to see a noticeable change in density ? the recommended?

Answer 17

5%. 15%

Question 18

when is the 15% rule used?

Answer 18

when you want to change the contrast of an image but keep the same density

Question 19

what factor do you adjust if you only want to change density only?

Answer 19

mAs

Question 20

what are the OTHER influencing factors for density?

Answer 20

focal spot size only from blooming
anode heel effect
distance 
filtration 
beam restriction
anatomical part 
grid
IR 
film speed

Question 21

what makes up the detail of an image?

Answer 21

contrast

Question 22

the difference between adjacent densities/IR exposure?

Answer 22

contrast

Question 23

define dynamic range:

Answer 23

contrast as it is displayed on a monitor in digital imaging

“range of brightness”

Question 24

what digital process controls brightness on a digital image?

Answer 24

window width

Question 25

what affects grayscale bit depth?

Answer 25

contrast/dynamic range/ ww on the z axis

Question 26

why is contrast hard to adjust?

Answer 26

because any change in density will effect contrast

Question 27

why is low contrast often desired?

Answer 27

it has more differences in density

Question 28

what are the two properties that make detail visible ?

Answer 28

density and contrast

Question 29

how do we manipulate contrast in film? digital?

Answer 29

kvp ww

Question 30

what are the 2 types of contrast?

Answer 30

IR contrast ( film/ digital) subject contrast these make up IMAGE CONTRAST

Question 31

what are the 4 factors that can affect IR contrast in film?

Answer 31

intensifying screen film density d log e curve processing

Question 32

digital IR contrast: as digital images go through post processing both the _______ and the ______ affect the final image contrast displayed

Answer 32

histogram and LUT note: the correct mAs and kvp must be chosen by the tech to ensure the correct exposure to the IR and desired differential attenuation

Question 33

define subject contrast:

Answer 33

the range of differences in the intensity of the X Ray beam AFTER attenuation

Question 34

subject contrast depends on:

Answer 34

kv, amount and type of tissue radiated

Question 35

higher kvp produces _____ contrast

Answer 35

decreased

Question 36

what type of interaction creates decreased contrast

Answer 36

Compton

Question 37

digital scatter causes ______ contrast

Answer 37

decreased

Question 38

how does AMOUNT of irradiated material affect contrast?

Answer 38

affects the number of X rays that reach the IR

Question 39

the anatomical structures of interest are visible only when ________ ________ exists between the densities

Answer 39

sufficient contrast

Question 40

what type of interaction causes high contrast

Answer 40

photoelectric interactions

Question 41

discerning contrast is difficult if an image has poor ___ _________

Answer 41

IR exposure/ density

Question 42

in digital, KVP can no longer be assessed by viewing the difference between densities or brightness......why?

Answer 42

the response curve is LINEAR

Question 43

what is the controlling factor of contrast? main influencing factor ?

Answer 43

kvp mAs

Question 44

OTHER influencing factors of contrast:

Answer 44

focal spot size (not likely ) anode heel effect. (very little effect) ``` distance filtration beam restriction anatomical part grid f/s combo processing ```

Question 45

what 3 things determine the actual recorded detail

Answer 45

matrix size pixel size grayscale bit depth