Absolute Quantification of Myocardial Blood Flow with H215O and 3-Dimensional PET: An Experimental Validation

The purpose of this study was to assess a 3-dimensional (3D)-only PET scanner (ECAT EXACT3D) for its use in the absolute quantification of myocardial blood flow (MBF) using H 2 15 O. Methods: Nine large white pigs were scanned with H 2 15 O and C 15 O before and after partially occluding the circumflex (n = 4) or the left anterior descending (n = 5) coronary artery at rest and during hyperemia induced by intravenous dipyridamole. Radioactive microspheres labeled with either 57 Co or 46 Sc were injected during each of the H 2 15 O scans, which allowed comparison between microsphere and PET measurements of regional MBF. PET analyses of 3D acquisition data were performed using filtered backprojection reconstruction and region-of-interest definition by factor and cluster analysis techniques and single-compartment model quantification. Results: The Hanning filter applied in image reconstruction resulted in a left atrial blood volume recovery factor of 0.84 ± 0.06. Differences between repeated measurements of recovery were small (mean, -0.8%; range, -6.6% to 3.6%). In 256 paired measurements of MBF ranging from 0.05 to 4.4 mL . g -1 . min -1 , microsphere and PET measurements were fairly well correlated. The mean difference between the 2 methods was -0.11 mL . g -1 . min -1 and the limits of agreement (+2 SD) were -0.82 and 0.60 mL . g -1 . min -1 (Bland-Altman plot). Conclusion: Dynamic measurements with H 2 15O using a 3D-only PET tomograph provide reliable and accurate measurements of absolute regional MBF over a wide flow range. The 3D acquisition technique can reduce the radiation dose to the subject while maintaining adequate counting statistics.