SPECT QC

Question 1

QC protocols for all systems

Answer 1

• Uniformity
• Intrinsic
• Extrinsic (system)
• Peaking
• Image linearity
• Spatial resolution
• Energy resolution
• Count rate response
• Sensitivity
• Collimator integrity
• WB uniformity

Question 2

QC protocols additional for SPECT

Answer 2

• High count uniformity
• Center of rotation
• System performance
• Spatial resolution
• Volume sensitivity
• Pixel sizing
• Multi-head registration
• Detector head alignment

Question 3

High Count flood

Answer 3

• Need a superior correction for system non-uniformities
• Do high count flood weekly/monthly
• ~30 million (64 matrix)
• ~120 million (128 matrix)
• 10,000 cts/pixel

Question 4

COR

Answer 4

• Frequency - weekly/monthly
• Determined by mechanical construction
• Evaluated with a point source
• Done for each clinical configuration

Question 5

System performance

Answer 5

• Evaluation of total system performance
• Frequency - monthly/quarterly
• Evaluates such parameters as:
• Contrast
• Noise
• Uniformity
• Linearity
• Resolution
• Accuracy of AC

Question 6

Spatial resolution

Answer 6

• Two aspects
• Transaxial (in-plane) resolution
• Axial resolution
• Qualitative and quantitative assessments

Question 7

Volume sensitivity

Answer 7

• Cylinder with known concentration of activity
• Count rate of 10,000 cps
• SPECT acquisition
• Turn off corrections
• SVS = [N / T]/A

Question 8

Pixel size callibration is required for..

Answer 8

• Attenuation correction
• Quantitation of volume

Question 9

Causes of variation include:

Answer 9

• Shift in gain
• Voltage drift
• Decreasing resolution of system

Question 10

Pixel size callibration

Answer 10

• Take an image of two point sources at a known distance apart on camera surface
• Identify the pixel location of each point source from the activity profile
• Pixel size= separation distance (mm)/#of pixles between peaks
• measure to 1/10th mm

Question 11

Multi-head registration

Answer 11

• COR of each head must have a common axis
• Literature varies on frequency

Question 12

Detector head alignment

Answer 12

• Heads must be aligned with the axis of rotation
• Assessed by collecting a 36-point image over 360 degrees
• Alternative - use carpenter’s bubble

Question 13

Artifacts

Answer 13

• Bullseye
• Ring
• Upward creep
• Hurricane Sign
• Streak
• Opposite sided defects
• Ghost artifacts
• Star
• Pixelation
• Edge packing
• PM tube failure
• Cracked crystal
• Voltage/gain drift
• Contamination
• Asymmetric window
• Moire effect
• Collimator damage