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

The objective of this study was to measure myocardial blood flow (MBF) in humans using ^99mTc-tetrofosmin and dynamic single-photon emission computed tomography (SPECT).

Dynamic SPECT using ^99mTc-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 ^99mTc-tefrofosmin while data from the remaining 7 patients were used for method validation. The nonlinear tracer correction parameters A and B for ^99mTc-tefrofosmin were estimated for the 9 patients by fitting the flow-extraction curve \( K_{1} = F\left( {1 - A \exp \left( { - \frac{B}{F}} \right)} \right) \) for K ₁ values estimated with ^99mTc-tefrofosmin using SPECT and MBF values estimated with ¹³N-NH₃ 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 ¹³N-NH₃ PET. The flow-dependent permeability surface-area product (PS) for ^99mTc-tefrofosmin was also estimated.

The estimated flow-extraction parameters for ^99mTc-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 ^99mTc-tefrofosmin was (0.019 ± 0.10)*MBF + (0.32 ± 0.16).

Dynamic cardiac SPECT using ^99mTc-tetrofosmin and a clinical two-headed SPECT/CT scanner can be a useful tool for estimation of MBF.