Spatial Resolution

Question 1

What are the three different ways “Spatial Resolution” can be defined

Answer 1

a. Smallest structures in an image measured in LP/mm
b. Sharpness of structural lines on an image
c. Ability to image adjacent objects separately

Question 2

What is the unit of measurement for spatial resolution?

Answer 2

line pairs/mm

Question 3

What do the line pairs represent?

Answer 3

the smallest size object the imaging system is able to visualizing

Question 4

define penumbra:

Answer 4

unsharpness in the image

Question 5

define umbra:

Answer 5

a lack of unsharpness in the image

Question 6

8 factors affecting spatial resolution

Answer 6

OID
SID
patient motion
filament size
anode angle
image display
size distortion
shape distortion

Question 7

define OID:

Answer 7

object to image distance

Question 8

increasing OID will lead to:

Answer 8

magnification

Question 9

decreasing OID will lead to:

Answer 9

less magnification

Question 10

What has the largest impact on magnification?

Answer 10

OID

Question 11

Why does OID create magnification?

Answer 11

beam divergence

Question 12

How do you double the size (2x mag.) of a body part?

Answer 12

always put the part half way between IR and source

Question 13

Which of the following has the greatest effect on reducing object magnification?

Answer 13

decreasing OID

Question 14

OID produces magnification of the part… why is this undesirable?

Answer 14

penumbra

Question 15

What has a greater effect on spatial resolution?

Answer 15

OID

Question 16

What is the best way to reduce focal spot blur (besides choosing the filament)?

Answer 16

decrease OID

Question 17

What is the greatest way to reduce the effects of OID?

Answer 17

increase SID

Question 18

The best way to minimize magnification is to:

Answer 18

decrease OID
increase SID

Question 19

define SID:

Answer 19

anode target (source) to IR

Question 20

increasing SID will:

Answer 20

decrease magnification

Question 21

decreasing SID will:

Answer 21

increase magnification

Question 22

How is SID measured?

Answer 22

AFS to IR

Question 23

Decreasing SID does what to size distortion?

Answer 23

increases

Question 24

Increasing distance (SID) requires that the mAS be _____ in order to maintain image receptor exposure

Answer 24

increased

Question 25

The more magnified an object,

Answer 25

the less the spatial resolution

Question 26

SOD is defined as:

Answer 26

distance between anode target and the object imaged

Question 27

magnification formula:

Answer 27

MF = SID/SOD

Question 28

actual size formula:

Answer 28

actual size = image size/MF

Question 29

SOD formula:

Answer 29

SID - OID

Question 30

define AFS:

Answer 30

area of the anode target struck by electrons

Question 31

Which two factors determine the size of the AFS

Answer 31

filament size anode target angle

Question 32

the larger the AFS:

Answer 32

the worse the spatial resolution

Question 33

define EFS:

Answer 33

area projected onto patient

Question 34

the smaller the filament size:

Answer 34

the smaller the EFS and better the spatial resolution

Question 35

the smaller the anode angle:

Answer 35

the smaller the EFS and better the spatial resolution

Question 36

what size filament will always provide better spatial resolution?

Answer 36

small

Question 37

Why does a smaller filament produce a better spatial resolution?

Answer 37

less divergence (less penumbra)

Question 38

why does a larger filament create penumbra?

Answer 38

because there is more divergence

Question 39

define focal spot blur:

Answer 39

blurred region of a radiograph that the tech has little control

Question 40

decreasing OID will do what to focal spot blur?

Answer 40

reduce

Question 41

The line focus principle states:

Answer 41

An anode angle of less than 45° will produce a smaller EFS than the FSS

Question 42

The advantage of the line focus principle is that it simultaneously improves:

Answer 42

spatial resolution and heat capacity

Question 43

why would we want to make the AFS larger than the filament size?

Answer 43

more ability to dissipate heat

Question 44

lesser angles produce:

Answer 44

sharper images

Question 45

1. larger anode angle = ______ heat dissipation 2. smaller anode angle = ______ heat dissipation 3. larger filament = ______ AFS 4. smaller filament = ______ AFS 5. larger EFS = ______ beam div. and ______ spatial resolution 6. smaller EFS = ______ beam div. and ______ spatial resolution

Answer 45

1. greater 2. less 3. larger 4. smaller 5. increased; decreased 6. decreased; increased

Question 46

patient motion will always cause:

Answer 46

a loss in spatial resolution

Question 47

Two types of distortion:

Answer 47

size and shape

Question 48

Which type of image distortion is called “true distortion?”

Answer 48

shape

Question 49

Why is shape distortion called "true distortion?"

Answer 49

it is actually changing the shape of something

Question 50

define shape distortion:

Answer 50

distortion of an objects shape

Question 51

What are the two types of shape distortion?

Answer 51

elongation and foreshortening

Question 52

Which type of shape distortion is created by the angling of the part?

Answer 52

foreshortening

Question 53

Which type of shape distortion results from angulation of the tube or IR?

Answer 53

elongation

Question 54

Which of the following can be done to decrease size distortion?

Answer 54

increase SID decrease OID

Question 55

Is shape distortion always bad?

Answer 55

no

Question 56

size distortion is only influenced by these 3 factors:

Answer 56

SID OID SOD (source to object)

Question 57

geometric factors affecting image quality:

Answer 57

magnification distortion (shape and size) focal spot blur they all cause blur!

Question 58

Which set of factors will provide the greatest spatial resolution?

Answer 58

small filament, small anode angle, small OID, large SID