ESTIMATION OF MYOCARDIAL BLOOD-FLOW FOR LONGITUDINAL-STUDIES WITH N-13 LABELED AMMONIA AND POSITRON EMISSION TOMOGRAPHY

Background, Although several modeling strategies have been developed a nd validated for quantification of myocardial blood flow (MBF) from N- 13-labeled ammonia positron emission tomographic data, a comparison of noise characteristics of the various techniques in serial studies is lacking. Methods and Results, Dynamic N-13-labeled ammonia positron em ission tomographic imaging was performed at baseline and after pharmac ologic stress in (1) single studies of four dogs with concomitant meas urement of microsphere blood flow and (2) initial and follow-up studie s of eight normal volunteers, Data were obtained from short-axis image s for the blood pool and myocardial regions corresponding to the three arterial vascular territories, Indexes of MBF were obtained by four d istinct techniques: (1) University of California, Los Angeles, two-com partment model, (2) Michigan two-compartment model, and (3) a one-comp artment model with variable blood volume term, Coronary flow reserve ( CFR) was measured as the ratio of stress/rest MBF. The estimated stand ard deviation of the measurement error for the relative change between studies of rest and stress MBF and CFR was determined for each techni que, Estimates of MBF from all techniques showed good correlation with microsphere blood flow (r = 0.95 to 0.96) in canine myocardium. In hu man studies, similar mean estimates of MBF were found with all techniq ues, Techniques 1 and 3 showed the smallest interstudy variability in MBE and CER, The estimated standard deviations for these techniques we re approximately 20%, 30%, and 27% for rest MBF, stress MBF, and CFR, respectively, Conclusion. Noninvasive quantification of MBF and CFR fr om dynamic N-13-labeled ammonia positron emission tomography is most r eproducible with technique 1 or 3, The ability to account for differen ces in myocardial partial volume gives preference to technique 3, Howe ver, substantial interstudy variability in regional MBF remains, sugge sting the importance of procedural factors or real temporal fluctuatio ns in MBF.