week 10: image quality cont.

Question 1

geometric properties of an x-ray is ________________________

Answer 1

how accurately the structural lines are recorded

Question 2

geometric qualities, degree of sharpness of structural lines

Answer 2

spatial resolution

Question 3

what is the leading cause of loss of recorded detail?

Answer 3

motion

Question 4

degree of sharpness of structural lines

Answer 4

spatial resolution

Question 5

results from radiographic misrepresentation of either the size (magnification) or the shape of the anatomic part

Answer 5

distortion

Question 6

what is the most common type of motion?

Answer 6

involuntary

Question 7

small focal spot (decreases/increases) recorded detail

Answer 7

increases

Question 8

what are the two types of inherent unsharpness

Answer 8

focal spot blur (penumbra), scatter

Question 9

What is the digital term for a loss of detail?

Answer 9

noise

Question 10

what is noise?

Answer 10

random fluctuation in the OD of the image

Question 11

lower noise is __________ contrast and recorded detail

Answer 11

improved

Question 12

a _____ signal (diagnostic information) to noise (un-diagnostic information) improves contrast and spatial resolution

Answer 12

higher

Question 13

what are the two types of distortion (general)

Answer 13

size and shape

Question 14

why is there always magnification in an image?

Answer 14

no anatomy can be directly up against the IR

Question 15

what do OID stand for?

Answer 15

object to image receptor distance

Question 16

what do SID stand for?

Answer 16

source to image receptor distance

Question 17

what do SOD stand for?

Answer 17

source to object distance

Question 18

what happens when you increase OID?

Answer 18

magnification increases; decreases recorded detail

Question 19

what happens when you increase SID?

Answer 19

magnification decreases; increases recorded detail

Question 20

what happens when you increase SOD?

Answer 20

magnification decreases; increases recorded detail

Question 21

what happens when you decrease OID?

Answer 21

magnification decreases; increases recorded detail

Question 22

what happens when you decrease SID?

Answer 22

magnification increases; decreases recorded detail

Question 23

what happens when you decrease SOD?

Answer 23

magnification increases; decreases recorded detail

Question 24

how is magnification calculated?

Answer 24

magnification factor = SID/SOD

Question 25

what does 3 part alignment do?

Answer 25

minimize shape distortion

Question 26

anatomy appears shorter than true object

Answer 26

foreshortening

Question 27

anatomy appears longer (wider) than true object

Answer 27

elongation

Question 28

Any misalignment of the CR among the three factors—___________________—will alter the shape of the part recorded on the image receptor.

Answer 28

tube, part, or image receptor

Question 29

why would we want shape distortion?

Answer 29

limitation of 2D image, can not see all anatomy of interest

Question 30

how do you get wanted shape distortion?

Answer 30

oblique the patient, axial of CR

Question 31

barium is considered to be ___________ contrast while air is considered to be ____________

Answer 31

positive, negative

Question 32

in terms of comparing film and digital contrast resolution, which gives more?

Answer 32

digital gives a higher contrast resolution?

Question 33

in terms of comparing film and digital spatial resolution, which gives more?

Answer 33

film gives higher spatial resolution

Question 34

as focal spot size increases, _________ also increases

Answer 34

focal spot blur