Comparison of coronary flow reserve estimated by dynamic radionuclide SPECT and multi-detector x-ray CT

Background: Recent technical advances in multi-detector computed tomography (MDCT) allow for assessment of coronary flow reserve (CFR). We compared regional CFR by dynamic SPECT and by dynamic MDCT in patients with suspected or known coronary artery disease (CAD). Methods: Thirty-five patients, (29 males, mean age 69 years) with greater than average Framingham risk of CAD, underwent dipyridamole vasodilator stress imaging. CFR was estimated using dynamic SPECT and dynamic MDCT imaging in the same patients. Myocardial perfusion findings were correlated with obstructive CAD (≥50% luminal narrowing) on CT coronary angiography (CA). Results: Mean CFR estimated by SPECT and MDCT in 595 myocardial segments was not different (1.51 ± 0.46 vs. 1.50 ± 0.37, p = NS). Correlation of segmental CFR by SPECT and MDCT was fair (r2 = 0.39, p < 0.001). Bland-Altman analysis revealed that MDCT in comparison to SPECT systematically underestimated CFR in higher CFR ranges. By CTCA, 12 patients had normal CA, 11 had non-obstructive, and 12 had obstructive CAD. CFR by both techniques was significantly higher in territories of normal CA than in territories subtended by non-obstructive or obstructive CAD. SPECT CFR was also significantly different in territories subtended by non-obstructive and obstructive CAD, whereas MDCT CFR was not. Conclusion: Despite relative underestimation of high CFR values, MDCT CFR shows promise for assessing the pathophysiological significance of anatomic CAD.