Influence of SPECT attenuation correction on the quantification of hibernating myocardium as derived from combined myocardial perfusion SPECT and ¹⁸F-FDG PET

To evaluate the influence of SPECT attenuation correction on the quantification of hibernating myocardium derived from perfusion SPECT and ¹⁸F-FDG PET.

20 patients underwent rest ^99mTc-tetrofosmin perfusion SPECT/CT and ¹⁸F-FDG PET/CT. Perfusion images were reconstructed without attenuation correction (NC), with attenuation correction based on the CT from the SPECT/CT (AC_SPECT), and with attenuation correction based on the CT from the PET/CT (AC_PET). Another 56 patients had rest ^99mTc-tetrofosmin perfusion SPECT and ¹⁸F-FDG PET/CT. Perfusion images were reconstructed as NC and AC_PET. The amounts of hibernating myocardium and scar were quantified with QPS^® and corresponding AC and NC normative databases. In both cohorts, perfusion in the inferior wall was higher in the AC scans than without AC. Global and regional values for total perfusion deficit (TPD), hibernation and scar areas did not differ between NC, AC_SPECT, and AC_PET scans. In a retrospective evaluation with 7% cut-off of hibernating myocardium as a condition for revascularization, the therapeutic approach would have been altered in 5 of 56 patients, if the AC_PET approach had been used.

AC of SPECT perfusion scans with an attenuation map derived from PET/CT scans is feasible. If AC is unavailable, perfusion scans should be compared to NC normative databases for assessing TPD, hibernation, and mismatch. It should be taken into account that in approximately 10% of the patients, a therapeutic recommendation based on published thresholds for hibernating myocardium would be altered if NC scans were used as compared to AC scans.