The PV method provides a rapid estimate for spatially variant patient-specific image noise magnitude in a pinhole-collimated dedicated cardiac SPECT camera with a bias of -0.3% and better than 83% precision.

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Background: Noninvasive quantification of absolute myocardial blood flow (MBF) and myocardial flow reserve (MFR) provides incremental benefit to relative myocardial perfusion imaging (MPI) to diagnose and manage heart disease. MBF can be measured with single-photon emission computed tomography (SPECT) but the uncertainty in the measured values is high. Standardization and optimization of protocols for SPECT MBF measurements will improve the consistency of this technique. One element of the processing protocol is the choice of kinetic model used to analyze the dynamic image series. Purpose: This study evaluates if a net tracer retention model (RET) will provide a better fit to the acquired data and greater test-retest precision than a one-compartment model (1CM) for SPECT MBF, with (+MC) and without (-MC) manual motion correction. Methods: Data from previously acquired rest-stress MBF studies (31 SPECT-PET and 30 SPECT-SPECT) were reprocessed ± MC. Rate constants (K1) were extracted using 1CM and RET, +/-MC, and compared pairwise with standard PET MBF measurements using cross-validation to obtain calibration parameters for converting SPECT rate constants to MBF and to assess the goodness-of -fit of the calibration curves. Precision (coefficient of variation of test re-test relative differences, COV) of flow measurements was computed for 1CM and RET ± MC using data from the repeated SPECT MBF studies. Results: Both the RET model and MC improved the goodness-of -fit of the SPECT MBF calibration curves to PET. All models produced minimal bias compared with PET (mean bias < 0.6%). The SPECT-SPECT MBF COV significantly improved from 34% (1CM+MC) to 28% (RET+MC, P = 0.008). Conclusion:The RET+MC model provides a better calibration of SPECT to PET and blood flow measurements with better precision than the 1CM, without loss of accuracy. K E Y W O R D S myocardial blood flow (MBF), myocardial flow reserve (MFR), net tracer retention model, precision, SPECT, tissue compartment model

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The originally published version of this article contained typographical errors in the units of photon sensitivity. The units of counts Á MBq-1 Á min-1 and kcounts Á mCi-1 Á min-1 were mistakenly recorded as counts Á MBq Á min and kcounts Á mCi Á min respectively. The original article has been corrected. Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Introduction: Myocardial blood flow (MBF) imaging with SPECT is possible using cardiac-specific cameras. Single-center studies have shown that SPECT MBF is accurate compared with PET MBF and angiography. Clinical implementation requires consistency of SPECT MBF measurements across multiple sites. This study is the first multi-center evaluation of the inter-site processing variability of SPECT MBF. Objective: To compare SPECT MBF obtained locally to MBF calculated at the core lab in Ottawa, Canada. Methods: Six sites (2 in Canada and one each from Japan, Singapore, Italy, and Germany) each acquired 25 rest/stress MBF studies using Tc99m-tetrofosmin (377 MBq at rest; 1060 MBq at stress) on a pinhole-collimated cadmium-zinc-telluride(CZT)-based cardiac SPECT camera. Patients had intermediate to high pre-test probability of coronary artery disease. MBF was analyzed locally and at a core lab using commercially available software. The time that a room was occupied for a MBF study was compared to that for a standard rest/stress myocardial perfusion study. Results: Preliminary results from 4 sites showed a correlation in MBF between the core lab and the local site of an average of 0.96 (range 0.95 to 0.97) at rest and 0.89 (range 0.77 to 0.96) at stress. From Bland-Altman analysis, the mean bias from zero in global MBF between local and core-lab analysis was 3.3% +/- 13.4% at rest and 3.0 % +/- 18.6% at stress. Between the 4 sites, the bias ranged from -4.1% to 9.9% at rest and from -6.3% to 12.8% at stress; the standard deviation (SD) ranged from 10.5% to 14.0% at rest and from 12.0% to 24.5% at stress. There was no significant difference between sites in the SD. The SD of the local-to-core-lab MBF differences is less than the SD of the test-retest difference of 30%, measured in a previous single-center study. The average additional time to perform a MBF study acquisition varied between sites from 45 to 76 min. This additional time includes the time needed to pharmacologically stress the patient which is normally done outside the camera room. Conclusions: This multi-center evaluation supports the feasibility of consistently measuring MBF using CZT-based cardiac SPECT cameras, as has been suggested from previous single-center studies.

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