Unit 2 Quality Factors III: Details and Distortion

Question 1

Spatial Resolution

Answer 1

Degree of sharpness of structural lines in a radiographic image

Question 2

Distortion

Answer 2

Misrepresentation of the size shape of the part being examined

Question 3

Controlling factors for Recorded Details

Answer 3

-Geometric Factors: Focal Spot Size, Imaging Distances
-Image Receptor: Equipment Speed
-Motion: Patient movement, Equipment movement

Question 4

Controlling factors for Distortion

Answer 4

Geometric factors: Imaging Distances, Part/IR/CR Alignment

Question 5

Does a small or large Focal Spot size produce images with better detail?

Answer 5

Small

Question 6

Spatial Resolution is improved at a ______ SID

Answer 6

Long

Question 7

________ angle produces higher spatial resolution

Answer 7

Smaller

Question 8

Penumbra

Answer 8

-Image blur, not detailed/sharp

Question 9

How do you asses exposure?

Answer 9

With the S number

Question 10

Penumbra Formula

Answer 10

GU = FS (OID)
————
SOD

Question 11

An increased SID = ___________ spatial resolution
A decreases SID = ___________ spatial resolution

Answer 11

Increased;
Decreased

Question 12

Source to Object Distance (SOD) equation

Answer 12

SID-OID = SOD

Question 13

Screen Speed

Answer 13

Describes how sensitive the IR is to radiation
-Higher Speed = More Sensitive to radiation = Less radiation needed
to produce quality images

Question 14

What is the trade off for higher screen speed?

Answer 14

Reduced Spatial Resolution/Detail at higher speeds

Question 15

Spatial Resolution is measured using

Answer 15

Line pair test tool

Question 16

Line pair test tool

Answer 16

-Measures Focal Spot resolution
-More visible line pairs = better spatial resolution

Question 17

Types of Motion

Answer 17

-Voluntary:
• Under direct control of patient
• Communication
-Involuntary:
• Not under conscious control of patient
• Reduced Exposure times & Immobilization
-Equipment:
• Ensure equipment is stable for exposure

Question 18

How do you reduce exposure time for Involuntary Motion

Answer 18

-Increase mA, cut down time
-Increase kVp by 15%

Question 19

RECORDED DETAIL VS. VISIBILITY OF DETAIL

Answer 19

Recorded detail:
• FS
• SID/OID
• Screen Speed
• Motion

Visibility of detail:

• Scatter
• Artifacts

Question 20

If an image has good spatial resolution, what 2 factors might cause reduced visibility of detail

Answer 20

Scatter and Artifact

Question 21

What is the ONLY possible size distortion in radiography?

Answer 21

Magnification

Question 22

Size Distortion

Answer 22

• Misrepresentation of the size of an object
• Magnification

Question 23

Is minimization possible for magnification/distortion?

Answer 23

No

Question 24

Size distortion controlling factors

Answer 24

• SID
• OID

Question 25

Magnification is reduced at a _______ SID

Answer 25

Long

Question 26

Magnification is increased at a _______ SID

Answer 26

Short

Question 27

Magnification Factor Equation

Answer 27

M = I
—
0

I = SID or Image Size
0 = SOD or Obiect Size
M = Magnification Factor

Question 28

SHAPE DISTORTION

Answer 28

Elongation: Project objects so they appear longer than they are
-Tube and IR not aligned
Foreshortening: Project objects so they appear shorter than they are
-Part and IR not aligned