Review ArticleProperties of an ideal PET perfusion tracer: New PET tracer cases and data
Introduction
Positron emission tomography (PET) myocardial perfusion imaging (MPI) has been technically feasible for many years, but wide acceptance has been hindered by the requirement for an on-site cyclotron to generate the radiotracers, the drawbacks of available radiotracers, limited numbers of PET scanners, and financial considerations. With the increasing availability of better cameras, more consistent reimbursement, and the availability of tracers that do not require an on-site cyclotron, these limitations are being addressed.
Section snippets
PET Myocardial Perfusion Tracers
Nitrogen-13 ammonia (13NH3) and oxygen-15 water () are excellent PET tracers,1,2 but few clinical sites have the on-site cyclotron required to produce them. The introduction of rubidium-82 (82Rb),3 which can be produced locally with a generator, expanded the reach of PET MPI into more hospitals and imaging centers. Rubidium-82, however, is not an ideal tracer. The high and recurring cost of the generator requires a high patient volume to make its use cost-effective. Image resolution with 82
Clinical Studies with Flurpiridaz F 18
Phase 1 and Phase 2 clinical studies have been completed with flurpiridaz F 18, and Phase 3 studies are currently ongoing.
Preliminary Comparison of Flurpiridaz F 18 PET and 99mTc SPECT Imaging
The author summarizes here his experience with 9 patients enrolled at the UCLA Medical Center. Perfusion abnormalities were detected by both SPECT and PET in 6 patients who had abnormal angiography results. Angiography results from the remaining 3 patients were normal, and no perfusion abnormalities were detected with PET in any of the 3 patients. SPECT images demonstrated that 2 of the 3 angiographically normal patients had no perfusion abnormalities, but detected an abnormality in the third
Preliminary Results of Absolute Quantification of MBF Using Flurpiridaz F 18
Absolute quantification of MBF with PET represents a major advantage over SPECT MPI and is a potential “game-changer” in the noninvasive evaluation of CAD. Decades of studies with 13NH3 and have shown that absolute quantification of MBF allows better identification of multivessel disease, assessment of the severity of microvascular disease, and also allows evaluation of endothelial dysfunction and responses to treatment.18 One of the limitations of imaging relative perfusion (as is done
Conclusion
Wider utilization of PET myocardial perfusion imaging has been limited by the choice of available radiopharmaceuticals. Of those currently in use, 13NH3 and require an on-site cyclotron, and thus are impractical for widespread utilization. Rubidium-82 may be prepared on site using a generator. But because of its long positron range, low myocardial extraction fraction, short half-life, incompatibility with exercise-stress imaging, and high recurrent costs, 82Rb has proved to be a
Disclosure
Dr Maddahi reported receiving grant support from Lantheus Medical Imaging. He reported being part of the speakers’ bureau with Astellas Pharmaceuticals. He reported being part of the advisory board for Digirad Corporation, Lantheus Medical Imaging, and Astellas Pharmaceuticals. He reported receiving honoraria from Digirad Corporation and Lantheus Medical Imaging.
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