Description
Positron Emission Tomography
PET scans coupled position-emitting radionuclide tracers to other molecules, such as glucose, ammonia, or water. The radionuclide tracers simultaneously emit two high-energy photons in opposite directions that can be simultaneously detected (referred to as
coincidence detection
) by a PET scanner, which comprises multiple stationary detectors that encircle the region of interest.
A variety of tracers are used for PET scanning, including oxygen 15, nitrogen 13, carbon 11, and fluorine 18. The radiotracer most commonly used in oncology imaging has been fluorine 18, coupled with fluorodeoxyglucose (FDG), which has a metabolism related to glucose metabolism. While FDG has traditionally been used in cancer imaging, it potentially has many other applications.
Summary of Evidence
For individuals with epileptic seizures who are candidates for surgery who undergo fluorine 18 fluorodeoxyglucose tomography ([FDG]-PET), the evidence includes systematic reviews (following the publication of three (3) TEC Assessments). Relevant outcomes are symptoms, change in disease status, functional outcomes, health status measures, quality of life (QOL), hospitalizations, medication use, and resource utilization. The TEC Assessments and Program in Evidence-based Care PET recommendation report all concluded that FDG-PET accurately localizes the seizure focus compared with appropriate reference standards. A recent systematic review suggested it was difficult to discern the incremental value of FDG-PET in individuals who have foci well localized by ictal scalp electroencephalography (EEG) and magnetic resonance imaging (MRI). The evidence on whether FDG-PET has a predictive value for a good surgical outcome is mixed. The evidence is sufficient to determine that the technology results in an improvement in the net health outcome.
For individuals with suspected chronic osteomyelitis who receive FDG-PET, the evidence includes meta-analyses and a prospective study published after the meta-analyses. Relevant outcomes are test accuracy and validity, other test performance measures, change in disease status, functional outcomes, QOL, and hospitalizations. One systematic review and meta-analysis from 2013 of nine (9) studies revealed that FDG-PET and FDG-PET plus computed tomography were useful for diagnosing suspected osteomyelitis in the foot of individuals with diabetes. The results of another meta-analysis showed that FDG-PET was the most accurate mode (pooled sensitivity, 96%; pooled specificity, 91%) for diagnosing chronic osteomyelitis. The results appear to be robust across fairly diverse clinical populations, which strengthen the conclusions. The evidence is sufficient to determine that the technology results in an improvement in the net health outcome.
For individuals with suspected large vessel vasculitis who receive FDG-PET, the evidence includes six (6) systematic reviews of observational studies and an observational study. Relevant outcomes are test accuracy and validity, other test performance measures, symptoms, morbid events, QOL, hospitalizations, and treatment-related morbidity. Most studies included in the reviews were small and lacked controls. The reported performance characteristics were heterogeneous but reviewers were unable to determine the source of heterogeneity. Studies comparing PET with the true reference standard of biopsy or angiography are rare. There are no consensus criteria to define the presence of vascular inflammation by FDG-PET in large vessel vasculitis, and different parameters with visual and semiquantitative methods have been reported. Studies demonstrating changes in management based on PET results or improvements in clinical outcomes are lacking. The evidence is insufficient to determine that the technology results in an improvement in the net health outcome.
For individuals with diverse noncardiac or nononcologic conditions (e.g., central nervous system, pulmonary, and musculoskeletal diseases) who receive FDG-PET, the evidence includes several systematic reviews. Relevant outcomes are overall survival, symptoms, change in disease status, functional outcomes, health status measures, QOL, hospitalizations, medication use, and resource utilization. Many studies cited in the reviews were small, retrospective, and published in the 1990s to early 2000s. Further, many studies did not directly compare a modality with another in the same individual group, nor did they correlate PET results in individual individuals with improved clinical outcomes. Additional studies are needed to demonstrate that FDG-PET results can change management, and therefore improve individual outcomes to support the utility of FDG-PET. The evidence is insufficient to determine that the technology results in an improvement in the net health outcome.
