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

Abstract

Background 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). Methods 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 K1=Ftrue(1−Aexptrue(−BFtrue)true) for K1 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. Results The estimated flow extraction parameters for 99mTc-tefrofosmin was found to be A=0.91±0.11, B=0.34±0.20 (R2 = 0.49). The range of MBF in LAD, RCA, and LCX was 0.44 ml/min/g to 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 < 0.001). However, the corresponding CFR correlation was moderate r = 0.39 yet statistically significant (p = 0.037). The PS for 99mTc-tefrofosmin was (0.091 ± 0.10) * MBF = (0.32 ± 0.16). Conclusions Dynamic cardiac SPECT using 99mTc-tetrofosmin and a clinical two-headed SPECT/CT scanner can be a useful tool for estimation of MBF.

Single Photon Emission Computed Tomography (SPECT) Myocardial Perfusion Imaging Guidelines: Instrumentation, Acquisition, Processing, and Interpretation

“…The feasibility of this approach has been demonstrated in a large animal model, 155 but at this time SPECT MBF and MFR measurements in humans are very new. While the results have been very encouraging, investigations with both conventional rotating systems 156,157 and non-rotating cardiac cameras 15,17,158,159 have been limited to single-center feasibility studies. While the benefits of PET-based MBF/MFR are clear, [160][161][162][163] no published study has currently evaluated the incremental diagnostic and prognostic value of SPECT MBF and MFR measurements; more investigations are ongoing in this area.…”

Myocardial blood flow from SPECT

“…In this issue of Journal of Nuclear Cardiology, a study by Shershta et al 5 analyzes the feasibility results of dynamic flow measurements with 99m Tc-tetrofosmin SPECT. Several methodological aspects of this study merit highlighting.…”

SPECT quantification of myocardial blood flow: A journey of a thousand miles begins with a single step (Lao Tzu, Chinese philosopher, 604-531 BC)

“…While there is not yet an accepted 'standard basis' for 4D image reconstruction, the authors have shown promising results using their chosen shape functions in several earlier simulation and human studies. [3][4][5] If these shape functions can provide a good fit to the measured dynamic data, then the modeled tracer distribution or 'parametric images' can be visualized post hoc at any time point from the start to end of the scan. This has the potential to allow visualization of tracer uptake in very short time intervals (i.e., 5 seconds in the present study) but with the image quality and count statistics derived from the much longer dynamic scan.…”