Enhanced accuracy of cardiac 82Rb PET functional parameters with 16-compared to 8-gated imaging on a long-axial-field-of-view PET system: validation against echocardiography

INTRODUCTION: Left ventricular (LV) ejection fraction (EF) and volumes derived from ECG-gated 82Rb PET are clinically relevant, but their assessment can be impaired due to limited temporal sampling and low count statistics. Long axial field-of-view (LAFOV) PET/CT systems provide substantially higher temporal resolution compared to standard, analog PET systems, which allows to yield higher sensitivity without the need for increasing tracer activity. We aimed to evaluate, whether increasing ECG gating from 8 to 16 frames on 82Rb LAFOV PET improves the accuracy of LV functional parameters. To that end, we used transthoracic echocardiography (TTE) as reference of standard. MATERIALS AND METHODS: We retrospectively included 124 consecutive patients undergoing clinically indicated rest–stress 82Rb PET/CT on a LAFOV system. All patients received 370 MBq 82Rb for both rest and stress acquisitions. Rest images were reconstructed using both 8- and 16-gated frames. PET-derived LVEF, end-diastolic volume (EDV), and end-systolic volume (ESV) were compared with TTE values obtained within a median of 26 days. Agreement was assessed using Wilcoxon test, Pearson correlation, and Bland–Altman analysis. RESULTS: Mean rest LVEF was 52.3 ± 15.5% with 8-gated PET, 58.1 ± 13.5% with 16-gated PET, and 57.7 ± 9.7% on TTE. LVEF derived from 16-gated PET showed no significant difference compared with TTE (p = 0.24), with fair correlation (r = 0.58) and minimal bias (+ 1.13%). In contrast, 8-gated PET significantly underestimated LVEF compared with TTE (mean bias − 5.49%, p < 0.001; r = 0.38), particularly at lower LVEF values. EDV was comparable between 8- and 16-gated PET but showed modest overestimation versus TTE for both reconstructions. For ESV, 8-gated PET significantly overestimated values compared with TTE (p = 0.002), whereas 16-gated PET showed improved agreement with no statistically significant difference (p = 0.085). CONCLUSION: On LAFOV PET/CT, increasing temporal resolution from 8 to 16 ECG-gated frames significantly improves the accuracy of LV functional assessment, particularly for ESV and LVEF, yielding close agreement with TTE. These improvements were achieved using low 82Rb activities, supporting the routine clinical implementation of 16-gated protocols on LAFOV systems to enhance functional cardiac assessment without increasing radiation burden.