unit 5 review

Question 1

degree of geometric sharpness or accuracy of the structural lines of the image

Answer 1

recorded detail

Question 2

what is the resolution of an image dependent on

Answer 2

pixel size(pitch), matrix size, & bit depth

Question 3

how does phosphor layer thickness effect resolution

Answer 3

the thinner the phosphor layer the higher (better) the resolution

Question 4

do you want a system with high or low spatial resolution?

Answer 4

high spatial resolution

Question 5

what is the measurement of lines that can be seen on an image

Answer 5

spatial frequency

Question 6

how is the trueness of an image determined

Answer 6

modulation transfer function (MTF) - measures the spread of light

Question 7

anything that interferes with the formation of an image

Answer 7

noise

Question 8

why would an image have a mottled appearance

Answer 8

lack of incoming photons to expose the IR , not enough mAs (increase/repeat)

Question 9

the mathematical measurement of noise

Answer 9

noise power spectrum

Question 10

do you want a high or low SNR , why?

Answer 10

high SNR , decreases noise

Question 11

the processing function that averages the incoming analog data between the image detector elements (samples / scans pixels twice)

Answer 11

nyquist theory

Question 12

what controls the sharpness of detail post processing

Answer 12

spatial frequency resolution

Question 13

what are they types of motion

Answer 13

voluntary, involuntary, & equipment motion (moving grids)

Question 14

how to control involuntary motion

Answer 14

decrease exposure time

Question 15

how to control voluntary motion

Answer 15

communication

Question 16

how to control equipment motion

Answer 16

lock equipment

Question 17

how do distances effect detail

Answer 17

increase distance, increase detail

Question 18

when you increase OID , detail

Answer 18

decreases

Question 19

misinterpretation of size or shape of the structure being x rayed

Answer 19

distortion

Question 20

types of distortion

Answer 20

size & shape (elongation & foreshortening)

Question 21

factors affecting distortion

Answer 21

distances (SID), (OID), direction of angle, angle of part, CR, & IR

Question 22

how is distortion & magnification calculated

Answer 22

M = SID over SOD

Question 23

how to calculate actual size

Answer 23

object size = image size over mag factor

Question 24

to avoid distortion - tube alignment

Answer 24

the part and IR must always be parallel & CR perpendicular

Question 25

one of 2 geometric properties of the image (other is distortion)

Answer 25

recorded detail

Question 26

other names for recorded detail

Answer 26

definition, sharpness, spatial resolution, detail

Question 27

ability to record 2 adjacent structures as separate structures

Answer 27

definition

Question 28

determined by matrix size, pixel size, and grayscale bit depth

Answer 28

recorded detail in digital imaging

Question 29

the best spatial resolution has what kind of contrast

Answer 29

high contrast for small structures

Question 30

what matrix size improves spatial resolution

Answer 30

larger matrix size

Question 31

as resolution increases

Answer 31

recorded detail increases

Question 32

the number of lines per millimeter that can be seen

Answer 32

special frequency

Question 33

higher special frequency has

Answer 33

higher spatial resolution

Question 34

expresses the boundaries of an image by testing the sharpness of lines

Answer 34

point spread function

Question 35

fidelity or trueness of an image

Answer 35

modulation transfer function (MTF)

Question 36

a system with an MTF of 1 would be

Answer 36

100% accurate

Question 37

as background noise increases

Answer 37

image noise increases

Question 38

SNR

Answer 38

signal to noise ratio

Question 39

the measurement of contrast change present in an image

Answer 39

contrast to noise

Question 40

to have a high CNR you must have

Answer 40

a high SNR

Question 41

provides increased resolution when motion is present , the relationship between the duration of data acquisition and motion of the structures being studied

Answer 41

temporal resolution (TR)

Question 42

shorter acquisition time will demonstrate

Answer 42

better TR (temporal resolution) - minimal motion

Question 43

digital imaging should at least sample the pixels

Answer 43

twice, in order to form image

Question 44

increases contrast & edge enhancement

Answer 44

high pass filtering

Question 45

removes high frequency noise, reduces contrast

Answer 45

smoothing - low pass filtering

Question 46

factors affecting recorded detail

Answer 46

geometry of the beam focal spot distance (SID) (OID) motion

Question 47

the distinctly sharp of a shadow or region of complete shadow

Answer 47

umbra

Question 48

area of unsharp shadow around umbra

Answer 48

penumbra

Question 49

as focal spot decreases, what happens to penumbra

Answer 49

decrease, increasing resolution

Question 50

what does image processing do?

Answer 50

sets limits on detail

Question 51

as motion increases

Answer 51

detail decreases

Question 52

best control for involuntary motion

Answer 52

decrease exposure time

Question 53

the only possible size distortion in radiography

Answer 53

magnification

Question 54

is minification possible in radiography

Answer 54

minification is impossible because of divergence of the beam

Question 55

misrepresentation by unequal magnification of the actual shape of the structure

Answer 55

shape distortion

Question 56

shape distortion results from

Answer 56

how structures normally lie in the body divergence of the x ray beam tube, part, & IR alignment

Question 57

object appears longer (tube or IR are improperly aligned)

Answer 57

elongation

Question 58

object appears shorter (part is improperly aligned)

Answer 58

foreshortening

Question 59

the tube angle will never cause

Answer 59

foreshortening

Question 60

how to avoid alignment distortion

Answer 60

part & IR must always be parallel & CR perpendicular

Question 61

when the nyquist theory isn’t met, the special frequency is greater than the inquest frequency

Answer 61

aliasing

Question 62

equation to find which image will have better spatial resolution

Answer 62

pixel = FOV / matrix size

Question 63

in image processing , what sets limits on detail

Answer 63

filtering, technical factors (LUT), histogram