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nmed 270 - qc1 > SPECT and CT QC (& Amy's Quizizz) > Flashcards

SPECT and CT QC (& Amy's Quizizz) Flashcards

1
Q

pixel size determination becomes especially important in SPECT imaging because it is needeed for:

A

Chang AC

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2
Q

There are typically __ lucite spheres in the Jaszczak phantom.

A

6

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3
Q

what piece of equipment is a rudimentary way to check for camera head tilt?

A

carpenters bubble

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4
Q

what does checking for rotational stability involve?

A

sheet source taped to the camera face

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5
Q

what is the ct number for water?

A

0

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6
Q

which of the following is not a correct assumption of radon’s theory for SPECT?
1. complete set of projections is obtained
2. internal distribution changes throughout acquisition
3. detectors have uniform sensitivity
4. COR is accurately known

A

2.
internal distribution is constant

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7
Q

the ______ is the line in space about which the gamma camera rotates for SPECT images.

A

AOR

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8
Q

what does the point source look like on a reconstructed transverse slice containing a 10-pixel COR offset error?

A

doughnut

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9
Q

the jaszczak phantom should be evaluated?
1. installation only
2. quarterly
3. weekly
4. annually

A

quarterly

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10
Q

During COR acquisition, the two 180 degree opposed projections of the pt source to which the centroid is found is known as?

A

conjugate pair

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11
Q

what is the purpose of acquiring high-count floods as part of a QC program?

A

for uniformity correction maps

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12
Q

a high count flood should have at least ___ million cts for a flood obtained with a 64x64 matrix.

A

30

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13
Q

a high count flood should have at least ___ million cts for a flood obtained with a 128x128 matrix.

A

120

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14
Q

T/F
if a hybrid system can perform a “Daily Air Calibration” it typically has a tube warmup built into the procedure.

A

True

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15
Q

T/F
Tc-99m is the only RN that requires a uniformity correction map for imaging purposes.

A

False.

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16
Q

COR QC should ideally be performed ___.

A

weekly

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17
Q

what is the limit for the standard deviation of the CT numbers within an ROI that is measuring noise?

A

<10

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18
Q

What are potential causes of COR errors?

A
  1. detector head weight - gravity
  2. camera head tilt
  3. changes in PMTs/amplifiers
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19
Q

When is a CT system considered cold?

A

when x-rays haven’t been fired in the last 2 hours

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20
Q

A COR x-axis offset of >0.5 pixels should warrant a _____ whereas an offset of >3 pixels should prompt a _____.

A

> 0.5 - repeat test
3 - service call

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21
Q

what is the first QC procedure that must be done prior to any other daily test for the CT component of a hybrid camera?

A

tube warmup

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22
Q

the rod insert section of the jaszczak phantom has a ____ sector format.

A

6

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23
Q

which is not true of CTDI testing?
1. performed by medical physicist
2. values need to be within +/- 20% of baseline values
3. only measures the periphery of phantom
4. can utilize phantoms shaped as a human torso

A

3.

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24
Q

center of the 3d image matrix is known as ___

A

COR

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25
Q

which section of the jaszczak phantom is the easiest for identifying any artifacts present?

A

uniformity section

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26
Q

when performing spect acq. on a gamma camera, it is best to ensure the camera planar uniformity is below…

A

3%

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27
Q

T/F
COR checks should be performed on all collimator systems used clinically.

A

true

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28
Q

system volume sensitivity is an example of a ____ test.

A

NEMA

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29
Q

which of the following CT tests are not performed by the technologist?
1. linearity of CT numbers
2. x-ray scatter and leakage
3. spatial reso
4. slice thickness

A

2

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30
Q

match the artifacts
- average energy of the x-ray beam is high due to attenuation of low energies
- averaging of detected densities in a given slice thickness

  • photon starvation

-incorrect placement of photon positioning

  • imperfect detector elements

beam hardening, partial volume, noise induced, scatter, ring

A

Beam hardening = average energy of the x-ray beam is high due to attenuation of low energies

partial volume = averaging of detected densities in a given slice thickness

noise induced = photon starvation

scatter = incorrect placement of photon positioning

ring = imperfect detector elements

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31
Q

When we are viewing transverse slices of the Jaszczak tomographic phantom that contain no rods or spheres present, we are evaluating:

A

reconstructive uniformity

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32
Q

When we are viewing transverse slices of the Jaszczak tomographic phantom that contain rods, we are evaluating:

A

spatial reso and linearity

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33
Q

When we are viewing transverse slices of the Jaszczak tomographic phantom that contain spheres, we are evaluating:

A

contrast

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34
Q

testing the tomographic uniformity of a CT system requires the placement of ___ ROIs.

A

5

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35
Q

the visual appearance of a reconstructed COR artifact on a SPECT that is performed over 180 degrees appears as a _____.

A

pitchfork

36
Q

T/F
non-uniformities aren’t present in reconstructed images unless rings or partial rings are seen.

A

false
sometimes they are very subtle

37
Q

what is the purpose of the COR QC?

A

to ensure that the focus of activity will be registered by all heads in the same 3D location

38
Q

T/F
each head needs to have its own COR study obtained from complete 360d rotation.

A

trueq

39
Q

time per stop should give ____ to _____ cts per 2D projection.

A

5k-20k

40
Q

when do we perform a COR calibration?

A
  1. when the offset is >0.5 pixel (after repeated fail check)
  2. installation
  3. after repair
41
Q

0.5 pixel offset error that is uncorrected will show a ___% degradation of spatial reso and a ___% loss of contrast.

A

30% degrade of spatial reso
40% loss of contrast

42
Q

0.1 pixel offset can lead to what kind of artifact?

A

halo/blurring

43
Q

frequency of high count floods?

A

weekly/biweekly
but most likely done monthly

44
Q

significant non-uniformities result in image artifacts of?

A

ring, bullseye

45
Q

what is rotational stability?

A

verification of system performance at several different angles; making sure the uniformity of the system is maintained during rotation of the heads

46
Q

for rotational stability we image with the camera at what degree(s)?

A

0, 90, 180, 270

47
Q

what do we want to see for the rotational stability test?

A

image that looks like noise

48
Q

what don’t we want to see for the rotational stability test?

A

areas of noticeable increase or deficit in ct density

49
Q

what is pixel size determination?

A

needed for Chang AC as the pixel size must be known to be within 0.5mm

50
Q

frequency of pixel size determination?

A

quarterly

51
Q

what would require attention when doing pixel size determination?

A
  • variation greater than a few percentage of pixel size between x and y directions
  • variation between heads
  • change from previous values
52
Q

what does collimator-hole angulation result in?

A

an amplification effect

53
Q

tilt angle check frequency?

A

quarterly

54
Q

when doing a tilt angle check the heads should be aligned with?

A

AOR

55
Q

what is system volume sensitivity?

A

compromise btw cts obtained and pt comfort/motion (imaging times)

56
Q

system volume sensitivity is an example of what kind of test?

A

NEMA

57
Q

how do we determine system volume sensitivity?

A

SVS = (total cts/total time [secs]) / activity concentration [uCi/mL]

58
Q

how do we determine sensitivity per axial cm?

A

SVS/length of phantom

59
Q

for non-uniformities, artifacts that have the greatest effects will be… (closer/farther) from AOR.

A

closest or at AOR

60
Q

nonuniformity rigs can be caused by?

A

poor detector uniformity, collimator defects, poor ct statistics in the uniformity correction data, scatter correction, ADC non-linearity

61
Q

what does daily QC for the CT subsystem include?

A
  • tube warmup
  • verification of tube output and detector response at various kVp and mA settings
  • tomographic uniformity
  • HU accuracy
  • image noise at clinical scanning parameters
62
Q

tomographic uniformity = <+/- ___ HU

A

<+/-2HU variation from ROI peripherally to center

63
Q

how do we test HU accuracy?

A

placing ROI in water and the mean CT number for water needs to be in range

64
Q

what is the range for the HU accuracy test?

A

0 +/- 4 HU

65
Q

frequency of CT spatial reso test?

A

monthly

66
Q

how is high contrast reso for CT tests done?

A

line-pairs phantom
- maximum # of visible lines per mm

67
Q

how is low contrast reso for CT tests done?

A

with phantoms containing objects varying sizes with small differences in densities from bkg
- it’ll be scanned at different mAs settings

68
Q

what results do we want for a low contrast reso test?

A

minimum that a density difference of 0.5% a 5mm object can be displayed

69
Q

Frequency of slice thickness accuracy?

A

Monthly

70
Q

How do we determine slice thickness accuracy?

A

Phantom that has ramps, spiral or step-wedge and known measurements

71
Q

In a 5mm or greater slice, what shouldn’t it vary more than +/- ___mm.

A

+/- 1mm

72
Q

In a slice that is smaller than 5mm, what shouldn’t it vary more than +/- ___mm.

A

+/- 0.5mm

73
Q

What is linearity in terms of CT tests?

A

The relationship between HU and LAC of scanned objects at a certain kVp

74
Q

How do we assess linearity for CT QC?

A

By scanning phantoms with known densities then we measure the objects and the plotted values should be a straight line between average HU and LAC

75
Q

Deviation from straight line indicates what? (On linearity test)

A

Scanner malfunction

76
Q

Frequency for laser light accuracy?

A

Semi annually

77
Q

In plane = ___ axis

A

X and Y axis

78
Q

Cross plane = ___ axis

A

Z axis

79
Q

What is calculated in plane?

A

PSF and MTF values
By phantom with a thin wire or special bar pattern

80
Q

What is calculated in cross plane?

A

Profile curve from ROI
Using phantom with thin disc or ramp

81
Q

Slice thickness for summed:
____ mm +/- ___ mm

A

1mm +/- 0.5mm

82
Q

Slice thickness for unsummed:
____ mm +/- ___ mm

A

0.8mm +/- 0.3 mm

83
Q

How many lexan pins are there?

A

7

84
Q

How do you determine low contrast detectability?

A

By windowing till you can see at least 5 pins

85
Q

What are some examples of CT acceptance tests?

A

Water cal, x-ray scatter and leakage, rotational gain cal, tomographic alignment, SPECT/CT alignment cal, x-ray collimator and detector alignment cal, anti-scattter grid alignment, geometry cal

nmed 270 - qc1 (6 decks)

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