Flurpiridaz F-18 PET superior to SPECT

Flurpiridaz F-18 PET myocardial perfusion imaging (MPI) outperformed SPECT MPI in terms of image quality, diagnostic certainty and sensitivity, according to a study published Jan. 22 in the Journal of the American College of Cardiology.

Disadvantages of existing MPI tracers, including limits in sensitivity and spatial resolution, have spurred the development of new radiotracers. Preclinical and Phase 1 studies of flurpiridaz F-18 PET have suggested linear myocardial uptake, high myocardial retention and low background in adjacent organs. It may be close to an ideal myocardial perfusion tracer, according to Daniel S. Berman, MD, from Cedars-Sinai Medical Center in Los Angeles, and colleagues.

Berman et al undertook a phase II study to evaluate the safety of flurpiridaz F-18 and compare it with SPECT MPI with respect to image quality, diagnostic certainty, magnitude of reversible perfusion defects and diagnostic efficacy for detection of coronary artery disease (CAD).

The researchers enrolled 143 patients; 107 were men and mean age was 62.5 years. They were stratified into three pre-test CAD likelihood categories: low (45 patients), intermediate (68 patients) and high (30 patients). A total of 86 patients comprised an angiography cohort with a truth standard for stenosis.

Sixty-one patients reported 108 adverse events; however, 100 of these were determined to be unrelated to the tracer. The remaining eight were considered possibly or probably related to the tracer and of mild or moderate severity that resolved without complications.

The radiation doses of the PET exams were approximately two times lower than those of standard rest/stress SPECT MPI, according to Berman and colleagues.

Three readers rated image quality, with 99.2 percent of flurpiridaz F-18 stress studies considered good or excellent compared with 88.5 percent of the SPECT studies. On rest studies, 96.9 percent of flurpiridaz F 18 were considered good or excellent, compared with 66.4 percent of SPECT exams.

Certainty of diagnosis was classified as definitely normal or definitely abnormal in 90.8 percent of patients by flurpiridaz F-18. On SPECT images, 70.9 percent of patients were classified as definitely normal or definitely abnormal.

“The improved image quality and diagnostic certainty are likely due to the great conspicuity of perfusion defects, improved resolution associated with F-18 PET, as well as the improved diagnostic certainty associated with the use of PET compared with SPECT and the use of attenuation correction for the PET studies,” wrote Berman et al.

Angiography showed 52 of the 86 patients had significant CAD. PET provided sensitivity of 78.8 percent, while SPECT provided sensitivity of 61.5 percent.

The researchers also found the frequency and magnitude of reversible perfusion defect was greater with PET than SPECT among patients with significant stenosis. Each reader noted the difference in magnitude.

“These findings suggest that this new tracer might significantly improve the assessment of patients with radionuclide MPI compared with the standard SPECT MPI methods,” concluded Berman and colleagues.