Clinical Blood Flow Measurement with [15O] Water and Positron Emission Tomography (PET)

Abstract

[15O]-labeled water has been used to measure brain blood flow for many years (Herscovitch, et al. 1983). While now considered a common procedure, it remains difficult to consistently perform quantitative PET blood flow measurements at most institutions. Blood flow as measured with [15O] H2O remains the only technique, in the majority of clinical PET centers, that can be performed very quickly and repeatedly to assess the cognitive state of a patient or research subject. The most widely used PET radiopharmaceutical, 2-[18F]fluoro-2-deoxy-D-glucose ([18F] FDG) clearly shows metabolic function of brain, heart or tumor. However, its long half-life (110 min) precludes performing repeat studies on the same day. Only one temporal assessment of function with [18F] FDG can be obtained when the patient is at the PET Center. The short half-life of [15O] (122 sec) permits multiple assessments to occur especially if intervention is planned (drug or cognitive activation). [15O] water can easily be produced on demand within a short time without significant radiochemistry involvement. Blood flow to other organs and tissues (bone marrow, heart or tumor) is also possible and is routinely performed at this institution.