Quantification of regional myocardial blood flow estimation with three-dimensional dynamic rubidium-82 PET and modified spillover correction model

Purpose. Myocardial blood flow (MBF) estimation with ⁸²Rubidium (⁸²Rb) positron emission tomography (PET) is technically difficult because of the high spillover between regions of interest, especially due to the long positron range. We sought to develop a new algorithm to reduce the spillover in image-derived blood activity curves, using non-uniform weighted leastsquares fitting. Methods. Fourteen volunteers underwent imaging with both 3-dimensional (3D) ⁸²Rb and ¹⁵O-water PET at rest and during pharmacological stress. Whole left ventricular (LV) ⁸²Rb MBF was estimated using a one-compartment model, including a myocardium-to-blood spillover correction to estimate the corresponding blood input function Ca(t)whole. Regional K1 values were calculated using this uniform global input function, which simplifies equations and enables robust estimation of MBF. To assess the robustness of the modified algorithm, interoperator repeatability of 3D ⁸²Rb MBF was compared with a previously established method. Results. Whole LV correlation of ⁸²Rb MBF with ¹⁵O-water MBF was better (P < .01) with the modified spillover correction method (r = 0.92 vs r = 0.60). The modified method also yielded significantly improved inter-operator repeatability of regional MBF quantification (r = 0.89) versus the established method (r = 0.82) (P < .01). Conclusion. A uniform global input function can suppress LV spillover into the imagederived blood input function, resulting in improved precision for MBF quantification with 3D ⁸²Rb PET.