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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
which section of the jaszczak phantom is the easiest for identifying any artifacts present?
uniformity section
26
when performing spect acq. on a gamma camera, it is best to ensure the camera planar uniformity is below...
3%
27
T/F COR checks should be performed on all collimator systems used clinically.
true
28
system volume sensitivity is an example of a ____ test.
NEMA
29
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
2
30
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
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
31
When we are viewing transverse slices of the Jaszczak tomographic phantom that contain no rods or spheres present, we are evaluating:
reconstructive uniformity
32
When we are viewing transverse slices of the Jaszczak tomographic phantom that contain rods, we are evaluating:
spatial reso and linearity
33
When we are viewing transverse slices of the Jaszczak tomographic phantom that contain spheres, we are evaluating:
contrast
34
testing the tomographic uniformity of a CT system requires the placement of ___ ROIs.
5
35
the visual appearance of a reconstructed COR artifact on a SPECT that is performed over 180 degrees appears as a _____.
pitchfork
36
T/F non-uniformities aren't present in reconstructed images unless rings or partial rings are seen.
false sometimes they are very subtle
37
what is the purpose of the COR QC?
to ensure that the focus of activity will be registered by all heads in the same 3D location
38
T/F each head needs to have its own COR study obtained from complete 360d rotation.
trueq
39
time per stop should give ____ to _____ cts per 2D projection.
5k-20k
40
when do we perform a COR calibration?
1. when the offset is >0.5 pixel (after repeated fail check) 2. installation 3. after repair
41
0.5 pixel offset error that is uncorrected will show a ___% degradation of spatial reso and a ___% loss of contrast.
30% degrade of spatial reso 40% loss of contrast
42
0.1 pixel offset can lead to what kind of artifact?
halo/blurring
43
frequency of high count floods?
weekly/biweekly but most likely done monthly
44
significant non-uniformities result in image artifacts of?
ring, bullseye
45
what is rotational stability?
verification of system performance at several different angles; making sure the uniformity of the system is maintained during rotation of the heads
46
for rotational stability we image with the camera at what degree(s)?
0, 90, 180, 270
47
what do we want to see for the rotational stability test?
image that looks like noise
48
what don't we want to see for the rotational stability test?
areas of noticeable increase or deficit in ct density
49
what is pixel size determination?
needed for Chang AC as the pixel size must be known to be within 0.5mm
50
frequency of pixel size determination?
quarterly
51
what would require attention when doing pixel size determination?
- variation greater than a few percentage of pixel size between x and y directions - variation between heads - change from previous values
52
what does collimator-hole angulation result in?
an amplification effect
53
tilt angle check frequency?
quarterly
54
when doing a tilt angle check the heads should be aligned with?
AOR
55
what is system volume sensitivity?
compromise btw cts obtained and pt comfort/motion (imaging times)
56
system volume sensitivity is an example of what kind of test?
NEMA
57
how do we determine system volume sensitivity?
SVS = (total cts/total time [secs]) / activity concentration [uCi/mL]
58
how do we determine sensitivity per axial cm?
SVS/length of phantom
59
for non-uniformities, artifacts that have the greatest effects will be... (closer/farther) from AOR.
closest or at AOR
60
nonuniformity rigs can be caused by?
poor detector uniformity, collimator defects, poor ct statistics in the uniformity correction data, scatter correction, ADC non-linearity
61
what does daily QC for the CT subsystem include?
- 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
tomographic uniformity = <+/- ___ HU
<+/-2HU variation from ROI peripherally to center
63
how do we test HU accuracy?
placing ROI in water and the mean CT number for water needs to be in range
64
what is the range for the HU accuracy test?
0 +/- 4 HU
65
frequency of CT spatial reso test?
monthly
66
how is high contrast reso for CT tests done?
line-pairs phantom - maximum # of visible lines per mm
67
how is low contrast reso for CT tests done?
with phantoms containing objects varying sizes with small differences in densities from bkg - it'll be scanned at different mAs settings
68
what results do we want for a low contrast reso test?
minimum that a density difference of 0.5% a 5mm object can be displayed
69
Frequency of slice thickness accuracy?
Monthly
70
How do we determine slice thickness accuracy?
Phantom that has ramps, spiral or step-wedge and known measurements
71
In a 5mm or greater slice, what shouldn’t it vary more than +/- ___mm.
+/- 1mm
72
In a slice that is smaller than 5mm, what shouldn’t it vary more than +/- ___mm.
+/- 0.5mm
73
What is linearity in terms of CT tests?
The relationship between HU and LAC of scanned objects at a certain kVp
74
How do we assess linearity for CT QC?
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
Deviation from straight line indicates what? (On linearity test)
Scanner malfunction
76
Frequency for laser light accuracy?
Semi annually
77
In plane = ___ axis
X and Y axis
78
Cross plane = ___ axis
Z axis
79
What is calculated in plane?
PSF and MTF values By phantom with a thin wire or special bar pattern
80
What is calculated in cross plane?
Profile curve from ROI Using phantom with thin disc or ramp
81
Slice thickness for summed: ____ mm +/- ___ mm
1mm +/- 0.5mm
82
Slice thickness for unsummed: ____ mm +/- ___ mm
0.8mm +/- 0.3 mm
83
How many lexan pins are there?
7
84
How do you determine low contrast detectability?
By windowing till you can see at least 5 pins
85
What are some examples of CT acceptance tests?
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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