Quiz 3

Question 1

What does an increase in SID primarily affect?

Answer 1

Size distortion - decrease
because of magnification

Question 2

How would an increase in SID affect IR exposure?

Answer 2

Decrease IR exposure

Question 3

How would an increase in OID affect IR exposure?

Answer 3

Decrease (Air Gap)

Question 4

An increase in SID would do what to sharpness?

Answer 4

Increase

Question 5

What factors does an increase in SID affect?

Answer 5

• Size Distortion: Decrease (Primary controller)
• IR Exposure: Decrease
• Sharpness: Increase

Question 6

What does an increase in OID primarily affect?

Answer 6

Sharpness - decrease

Question 7

Increased alignment does what to shape distortion?

Answer 7

Decrease

Question 8

What affects shape distortion?

Answer 8

Alignment

Question 9

What factors are affected by an increase in motion?

Answer 9

• Subject contrast goes down
• Noise (blur) goes up
• Sharpness goes down

Question 10

What primary factors are affected by an increase in SOD?

Answer 10

• Sharpness increase
• Size Distortion decreases

Question 11

How would an increase in OID affect subject contrast?

Answer 11

Increase (Air Gap)

Question 12

How would an increase in OID with air gap technique affect noise?

Answer 12

Decrease (Scatter)

Question 13

How would an increase in OID without air gap technique affect noise?

Answer 13

No effect on noise or contrast

Question 14

Increased OID with air gap leads to ______ exposure to the IR

Answer 14

Decreased because there is less scatter hitting the IR

Question 15

Increased OID leads to ______ penumbra and ______ spatial resolution

Answer 15

• Increase penumbra
• Decreased spatial resolution (detail and sharpness)

Question 16

What affects spatial resolution?

Answer 16

SID

Question 17

Where is the SID measured from?

Answer 17

Focal Spot to image receptor

Question 18

Why is the measuring tape on the collimator cut?

Answer 18

Accounts for focal spot to collimator

Question 19

What is the relationship of SID/SOD/OID?

Answer 19

SID = SOD + OID

Question 20

What is the square law used for?

Answer 20

Used to maintain IR exposure

Question 21

What is the inverse square law used for?

Answer 21

Used to determine intensity of exposure (mGy or mSv)

Question 22

What happens when AEC encounters metal?

Answer 22

Time, motion, patient exposure, and IR exposure all increase.

Question 23

Density settings of ____ are needed to see a visible change.

Answer 23

+2

Question 24

Backup time should be to ____% of anticipated time.

Answer 24

150%

Ex: Anticipated: 0.4 sec; Backup Time: 0.6 sec.

Question 25

Where is the AEC detector located?

Answer 25

Between the patient and the image receptor and use ionization.

Question 26

How many lonization chambers do most AEC Systems consist of?

Answer 26

3 (the cells on the wall bucky)

Question 27

Modulation Transfer Function

Answer 27

a. A way physicists measure contrast resolution b. When line pairs become too small their penumbrae merge and reduce contrast.

Question 28

Why do we have technique charts?

Answer 28

To maintain consistency

Question 29

The only thing AEC controls is:

Answer 29

Time

Question 30

Air Gap Technique is based on creating a gap by increasing the ___

Answer 30

OID

Question 31

Air Gap Technique

Answer 31

a. Increases Magnification b. Improves contrast c. Decreases detail (increases penumbra)

Question 32

Magnification is

Answer 32

Size distortion

Question 33

What is the magnification factor?

Answer 33

SID/SOD

Question 34

How would you determine an object size?

Answer 34

Projected Size/Magnification Factor

Question 35

What causes shape distortion?

Answer 35

Misalignment of tube, image receptor, or part

Question 36

Elongation is:

Answer 36

Angle on tube or IR anatomy appearing longer than normal

Question 37

Foreshortening is:

Answer 37

Part is angled appearing shorter than normal

Question 38

Off-centering is the same as:

Answer 38

Angling

Question 39

We should always have a minimum of ____ views

Answer 39

2

Question 40

What is Ceiszynski’s Law?

Answer 40

When objects are tilted in relation to the IR, minimum distortion is achieved by angling the CR ½ of the angle formed between the object and the IR. Ex: If the anatomy of interest is angled at 30°, the angle of the CR would be 15°.

Question 41

Motion is generally caused by:

Answer 41

Patients

Question 42

Increase SID = ____ IR Exposure

Answer 42

Increase SID = decrease intensity = decrease IR exposure X ray beam is divergent meaning photon beams spread out as they leave the xray tube. Closer to the tube the beams are more intense

Question 43

Increased focal spot size will _____ sharpness

Answer 43

Decrease. It is the one and only controller

Question 44

The smaller the focal spot size, the ______ spatial resolution

Answer 44

Higher

Question 45

What does the inverse square law mean?

Answer 45

The change in intensity due to the change in distance When distance increases the intensity (quantity) decreases When the intensity increases, the distance decreases.

Question 46

Increase in distance means a decrease in what three things

Answer 46

Intensity Patient dose IR Exposure

Question 47

What is the inverse square law equation and what is it used for

Answer 47

Eo/En = (Dn^2) / (Do^2) Used to determine a change in exposure if SID changes (INverse - INtensity)

Question 48

The inverse square law defines the relationship between what two factors?

Answer 48

Distance and beam intensity

Question 49

What is a primary factor of SID?

Answer 49

SIze Distortion (decrease)

Question 50

What is a primary factor of OID?

Answer 50

Sharpness. “OID - Ouch sharp” Increasing OID decreases shaprness

Question 51

What is the primary factor for SOD?

Answer 51

Sharpness (increase) AND Size Distortion (decrease) Think SOD is a mix of SID and OID and those factors are size distortion (SID) and sharpness (OID)

Question 52

What are the primary factors of collimation?

Answer 52

Subject Contrast (increases when collimation increases) Noise (scatter - decreases with increased collimation) “collimation - COntrast and Noise “Collimate out the nonsense)

Question 53

What is the Square Law equation (aka Density Maintenance Formula) and what is it used for

Answer 53

mAs o / mAs n = (Do)^2 / (Dn)^2 Used to determine new technique when SID changes so that exposure to the IR is maintained

Question 54

Increasing collimation will result in increased: A. IR Exposure B. Subject contrast C. Noise D. Spatial Resolution

Answer 54

B. Subject Contrast

Question 55

Increasing the OID will decrease: A. Shape distortion. B. Subject contrast. C. Size distortion. D. Sharpness.

Answer 55

D. Sharpness.

Question 56

Decreasing the focal spot size will result in: A. Increase contrast. B. Decrease contrast. C. Increase sharpness. D. Decrease sharpness.

Answer 56

C. Increased sharpness.

Question 57

Decreasing kVp will result in: A. Increased sharpness B. Decreased sharpness C. Increased IR Exposure D. Decreased IR Exposure

Answer 57

D. Decreased IR EXPOSURE

Question 58

Reducing mAs but adjusting kVp to compensate will result in decreased: A. IR exposure B. Size distortion C. Subject contrast D. Sharpness

Answer 58

C. Subject contrast.

Question 59

Reducing SID but adjusting mAs to compensate will result in decreased: A. Subject contrast. B. Sharpness. C. Noise. D. Size distortion.

Answer 59

B. Sharpness.

Question 60

Which one of the following pathologist would be MOST LIKELY to result in increased shape distortion? A. Emphysema B. Large bowel obstruction C. Kyphosis D. Cirrhosis

Answer 60

C. Kyphosis.

Question 61

A transthoracic humorous exam results in a radiograph that displays decreased subject contrast. If the image was repeated, which change would be MOST EFFECTIVE in improving subject contrast? A. Increase mAs B. Increase collimation C. Decrease motion D. Reduce kVp

Answer 61

B. Increase collimation