Category | Procedure | Uncertainties | Quality control |
Scanning protocol | Patient preparation | Metabolism levels (18F-FDG) | Limit physical activity |
Blood glucose levels (18F-FDG) | Measure fasting blood glucose with exclusion criteria | ||
Bowel size/positioning | Use fasting protocol | ||
Radiotracer injection | Residual activity in syringe | Measure/correct for residual activity | |
Decay correction errors | Synchronize scanner clock | ||
Acquisition | Patient positioning | Spatial offset between PET and treatment-planning CT | Ensure consistent patient positioning using identical positioning devices |
Quantitative uncertainties from attenuating objects | Avoid placing objects outside image field of view | ||
Scanning | Patient motion | Implement motion management strategies | |
Attenuation correction uncertainties from iodine contrast material | Acquire separate low-dose CT scan or apply corrections | ||
Equipment failure or electronic drift | Calibrate detector and equipment frequently | ||
Increased SUV because of longer uptake period | Apply strict protocol for uptake period | ||
Reconstruction | Reconstruction | Selection of optimal image reconstruction method/parameters | Benchmark algorithms using phantoms (task-specific) |
Randoms, scatter, attenuation, detector sensitivity, and partial-volume effect | Apply appropriate calibrations and corrections | ||
Analysis | Segmentation | Differentiation of normal tissue and tumor uptake | Know radiotracer’s normal biodistribution |
Segmentation uncertainties | Develop segmentation protocol; benchmark algorithms with phantoms | ||
Limited spatial resolution and sensitivity | Include margins | ||
Quantification | Quantitative accuracy | Calibrate PET scanner to dose calibrator | |
Selection of relevant quantitative measures | Compare semiquantitative metrics with kinetic analysis–derived parameters; consult literature | ||
Quantitative differences between scanners/institutions | Quantitatively harmonize scanners | ||
Treatment planning | Target definition | Registration errors | Benchmark algorithms using physical or digital phantoms; crop images |
Motion | Use same motion management method as was used during imaging |
Similar uncertainties exist for all other molecular imaging modalities, which require specific quality control measures.