Gated blood pool SPECT: The estimation of right ventricular volume and function is algorithm dependent in a clinical setting.

Background: Gated blood pool SPECT (GBPS) requires further validation for the assessment of the right ventricle (RV). This study evaluated three algorithms: BP-SPECT, QBS, and TOMPOOL (results are referred using this order). We compared (1) their "quantitative-accuracy": estimation of RV ejection fraction (EF), end-diastolic volume (EDV), and cardiac output (CO); (2) their "qualitative-accuracy": threshold values allowing diagnosing an impairment of the RV function; (3) their reproducibility: inter-observer relative variability (IOV).

Methods And Results: Forty-eight consecutive patients underwent GBPS. Recommended reference standards were used: cardiac magnetic resonance imaging (CMR) (EDV, EF, n = 48), catheter measurements from thermodilution (TD) (CO, n = 25). (1) "Quantitative-accuracy": r = 0.42, 0.30, 0.42 for RVEF (CMR); r = 0.69, 0.77, 0.53 for RVEDV (CMR); 0.32, 0.36, 0.52 for RCO (TD). (2) "Qualitative-accuracy": optimal thresholds were 54.7%, 38.5%, 45.2% (AUC: 0.83, 0.80, 0.79) for RVEF; 229, 180, 94 mL (AUC: 0.83, 0.81, 0.81) for RVEDV; 4.1, 4.4, 2.6 L·minute(-1) (AUC: 0.73, 0.77, 0.80) for RCO. (3) Reproducibility: IOV was 5% ± 6%, 8% ± 12%, 17% ± 18% for RVEF; 6% ± 8%, 4% ± 4%, 21% ± 18% for RVEDV; 8% ± 8%, 11% ± 15%, 24% ± 20% for RCO.

Conclusion: Diagnostic accuracies are similar. A CMR-based calibration is required for a quantitative-analysis (cautious interpretation) or an accurate qualitative analysis (thresholds must be adjusted). Automatic procedures (BP-SPECT, QBS) offer the best compromise accuracy/reproducibility.