Measurement of absolute myocardial blood flow in humans using dynamic cardiac SPECT and 99m Tc-tetrofosmin: Method and validation

Background The objective of this study was to measure myocardial blood flow (MBF) in humans using 99m Tc-tetrofosmin and dynamic single-photon emission computed tomography (SPECT). Methods Dynamic SPECT using 99m Tc-tetrofosmin and dynamic positron emission tomography (PET) was performed on a group of 16 patients. The SPECT data were reconstructed using a 4D-spatiotemporal iterative reconstruction method. The data corresponding to 9 patients were used to determine the flow-extraction curve for 99m Tc-tefrofosmin while data from the remaining 7 patients were used for method validation. The nonlinear tracer correction parameters A and B for 99m Tc-tefrofosmin were estimated for the 9 patients by fitting the flow-extraction curve K_1 = F( 1 - A exp( - B/F)) for K 1 values estimated with 99m Tc-tefrofosmin using SPECT and MBF values estimated with 13 N-NH 3 using PET. These parameters were then used to calculate MBF and coronary flow reserve (CFR) in three coronary territories (LAD, RCA, and LCX) using SPECT for an independent cohort of 7 patients. The results were then compared with that estimated with 13 N-NH 3 PET. The flow-dependent permeability surface-area product (PS) for 99m Tc-tefrofosmin was also estimated. Results The estimated flow-extraction parameters for 99m Tc-tefrofosmin were found to be A = 0.91 ± 0.11, B = 0.34 ± 0.20 ( R 2 = 0.49). The range of MBF in LAD, RCA, and LCX was 0.44-3.81 mL/min/g. The MBF between PET and SPECT in the group of independent cohort of 7 patients showed statistically significant correlation, r = 0.71 ( P < .001). However, the corresponding CFR correlation was moderate r = 0.39 yet statistically significant ( P = .037). The PS for 99m Tc-tefrofosmin was (0.019 ± 0.10)*MBF + (0.32 ± 0.16). Conclusions Dynamic cardiac SPECT using 99m Tc-tetrofosmin and a clinical two-headed SPECT/CT scanner can be a useful tool for estimation of MBF.