BASIC SCIENCE INVESTIGATIONS Absolute Quantification of Myocardial Blood Flow with H2O 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 H2O. Methods: Nine large white pigs were scanned with H2O and C15O 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 57Co or 46Sc were injected during each of the H2O 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 H2O 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.