Semi-quantitative assessment of ischemia with rubidium-82 PET myocardial perfusion imaging

Purpose: Semi-quantitative scores can be used as an adjunct to visual assessment in rubidium-82 positron emission tomography (⁸²Rb PET). The semi-quantitative cut-off values used in ⁸²Rb PET are derived from single-photon emission computed tomography (SPECT). It is unknown whether these cut-off values can be extrapolated to ⁸²Rb PET. We compared the semi-quantitative with the visual assessment of ischemia and determined which summed difference score (SDS) score predicts ischemia best.

Methods: We included 108 patients who underwent ⁸²Rb PET imaging and performed visual and semi-quantitative assessment. A scan with a SDS ≥ 2 and a summed stress score (SSS) ≥ 4 was considered to demonstrate ischemia. We compared the semi-quantitative with the visual assessment.

Results: 41 (38%) Normal scans, and 67 (62%) scans with ischemia and/or an irreversible defect were included. The semi-quantitative assessment showed ischemia more often than the visual assessment (51% vs 29%, P < .001). Patients with a low or intermediate pre-test probability of coronary artery disease (CAD) and a SDS < 4 did not demonstrate ischemia by visual assessment.

Conclusion: Semi-quantitative assessment in ⁸²Rb PET imaging clearly demonstrates the presence of ischemia. Ischemia is unlikely in patients with low and intermediate pre-test probability of CAD and a SDS < 4.