Excerpt

The capability of measuring myocardial blood flow (MBF) as a clinical routine is unique to cardiac PET. It is commonly expressed in units of mL/minute/gram of myocardium, and is quantitated in both rest and hyperemic (stress) conditions. Often, it is reported as a unitless ratio between stress and rest as coronary flow reserve (CFR) or myocardial blood flow reserve (MBFR). Both CFR and MBFR have been used; for purposes of this document, terminology will be confined to MBF and MBFR. Because rest MBF is affected by myocardial work, some investigators “normalize” the rest flows based on rest heart rate and systolic blood pressure. The PET tracers rubidium-82, O-15 water, and N-13 ammonia have all been extensively validated for flow quantitation,1-15 and there now exist commercially available software for the two tracers applicable to clinical settings: rubidium-82 and N-13 ammonia. MBF and MBFR are typically measured for each myocardial pixel, and then averaged within each of 17 myocardial segments, within coronary territories, and for the entire myocardium (a “global” quantitation). Both dedicated PET and new-generation hybrid PET/CT scanners are capable of quantitating MBF, the former typically involving dynamic acquisitions, sometimes requiring a separate injection of tracer, and the latter list-mode acquisitions, during which all of MBF, perfusion, and function assessments can be made with a single injection of tracer. …