Influence of residual oxygen-15-labeled carbon monoxide radioactivity on cerebral blood flow and oxygen extraction fraction in a dual-tracer autoradiographic method

摘要

Objective Cerebral blood flow (CBF), cerebral metabolic rate of oxygen (CMRO₂), oxygen extraction fraction (OEF), and cerebral blood volume (CBV) are quantitatively measured with PET with 15O gases. Kudomi et al. developed a dual tracer autoradiographic (DARG) protocol that enables the duration of a PET study to be shortened by sequentially administrating 15O₂ and C15O₂ gases. In this protocol, before the sequential PET scan with 15O₂ and C15O₂ gases (15O₂–C15O₂ PET scan), a PET scan with C15O should be preceded to obtain CBV image. C15O has a high affinity for red blood cells and a very slow washout rate, and residual radioactivity from C15O might exist during a 15O₂–C15O₂ PET scan. As the current DARG method assumes no residual C15O radioactivity before scanning, we performed computer simulations to evaluate the influence of the residual C15O radioactivity on the accuracy of measured CBF and OEF values with DARG method and also proposed a subtraction technique to minimize the error due to the residual C15O radioactivity.