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Rad Sci II > Quiz 3 > Flashcards

Quiz 3 Flashcards

1
Q

What does an increase in SID primarily affect?

A

Size distortion - decrease
because of magnification

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2
Q

How would an increase in SID affect IR exposure?

A

Decrease IR exposure

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3
Q

How would an increase in OID affect IR exposure?

A

Decrease (Air Gap)

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4
Q

An increase in SID would do what to sharpness?

A

Increase

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5
Q

What factors does an increase in SID affect?

A
  • Size Distortion: Decrease (Primary controller)
  • IR Exposure: Decrease
  • Sharpness: Increase
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6
Q

What does an increase in OID primarily affect?

A

Sharpness - decrease

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7
Q

Increased alignment does what to shape distortion?

A

Decrease

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8
Q

What affects shape distortion?

A

Alignment

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9
Q

What factors are affected by an increase in motion?

A
  • Subject contrast goes down
  • Noise (blur) goes up
  • Sharpness goes down
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10
Q

What primary factors are affected by an increase in SOD?

A
  • Sharpness increase
  • Size Distortion decreases
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11
Q

How would an increase in OID affect subject contrast?

A

Increase (Air Gap)

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12
Q

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

A

Decrease (Scatter)

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13
Q

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

A

No effect on noise or contrast

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14
Q

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

A

Decreased because there is less scatter hitting the IR

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15
Q

Increased OID leads to ______ penumbra and ______ spatial resolution

A
  • Increase penumbra
  • Decreased spatial resolution (detail and sharpness)
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16
Q

What affects spatial resolution?

A

SID

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17
Q

Where is the SID measured from?

A

Focal Spot to image receptor

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18
Q

Why is the measuring tape on the collimator cut?

A

Accounts for focal spot to collimator

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19
Q

What is the relationship of SID/SOD/OID?

A

SID = SOD + OID

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20
Q

What is the square law used for?

A

Used to maintain IR exposure

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21
Q

What is the inverse square law used for?

A

Used to determine intensity of exposure (mGy or mSv)

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22
Q

What happens when AEC encounters metal?

A

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

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23
Q

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

A

+2

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24
Q

Backup time should be to ____% of anticipated time.

A

150%

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

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25
Q

Where is the AEC detector located?

A

Between the patient and the image receptor and use ionization.

26
Q

How many lonization chambers do most AEC Systems consist of?

A

3 (the cells on the wall bucky)

27
Q

Modulation Transfer Function

A

a. A way physicists measure contrast resolution

b. When line pairs become too small their penumbrae merge and reduce contrast.

28
Q

Why do we have technique charts?

A

To maintain consistency

29
Q

The only thing AEC controls is:

A

Time

30
Q

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

A

OID

31
Q

Air Gap Technique

A

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

32
Q

Magnification is

A

Size distortion

33
Q

What is the magnification factor?

A

SID/SOD

34
Q

How would you determine an object size?

A

Projected Size/Magnification Factor

35
Q

What causes shape distortion?

A

Misalignment of tube, image receptor, or part

36
Q

Elongation is:

A

Angle on tube or IR

anatomy appearing longer than normal

37
Q

Foreshortening is:

A

Part is angled appearing shorter than normal

38
Q

Off-centering is the same as:

A

Angling

39
Q

We should always have a minimum of ____ views

A

2

40
Q

What is Ceiszynski’s Law?

A

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°.

41
Q

Motion is generally caused by:

A

Patients

42
Q

Increase SID = ____ IR Exposure

A

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

43
Q

Increased focal spot size will _____ sharpness

A

Decrease.
It is the one and only controller

44
Q

The smaller the focal spot size, the ______ spatial resolution

A

Higher

45
Q

What does the inverse square law mean?

A

The change in intensity due to the change in distance

When distance increases the intensity (quantity) decreases

When the intensity increases, the distance decreases.

46
Q

Increase in distance means a decrease in what three things

A

Intensity
Patient dose
IR Exposure

47
Q

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

A

Eo/En = (Dn^2) / (Do^2)

Used to determine a change in exposure if SID changes (INverse - INtensity)

48
Q

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

A

Distance and beam intensity

49
Q

What is a primary factor of SID?

A

SIze Distortion (decrease)

50
Q

What is a primary factor of OID?

A

Sharpness.

“OID - Ouch sharp”
Increasing OID decreases shaprness

51
Q

What is the primary factor for SOD?

A

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)

52
Q

What are the primary factors of collimation?

A

Subject Contrast (increases when collimation increases)

Noise (scatter - decreases with increased collimation)

“collimation - COntrast and Noise “Collimate out the nonsense)

53
Q

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

A

mAs o / mAs n = (Do)^2 / (Dn)^2

Used to determine new technique when SID changes so that exposure to the IR is maintained

54
Q

Increasing collimation will result in increased:

A. IR Exposure
B. Subject contrast
C. Noise
D. Spatial Resolution

A

B. Subject Contrast

55
Q

Increasing the OID will decrease:

A. Shape distortion.
B. Subject contrast.
C. Size distortion.
D. Sharpness.

A

D. Sharpness.

56
Q

Decreasing the focal spot size will result in:

A. Increase contrast.
B. Decrease contrast.
C. Increase sharpness.
D. Decrease sharpness.

A

C. Increased sharpness.

57
Q

Decreasing kVp will result in:

A. Increased sharpness
B. Decreased sharpness
C. Increased IR Exposure
D. Decreased IR Exposure

A

D. Decreased IR EXPOSURE

58
Q

Reducing mAs but adjusting kVp to compensate will result in decreased:

A. IR exposure
B. Size distortion
C. Subject contrast
D. Sharpness

A

C. Subject contrast.

59
Q

Reducing SID but adjusting mAs to compensate will result in decreased:

A. Subject contrast.
B. Sharpness.
C. Noise.
D. Size distortion.

A

B. Sharpness.

60
Q

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

A

C. Kyphosis.

61
Q

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

A

B. Increase collimation

Rad Sci II (3 decks)

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