Proposal of blood volume-corrected model for quantification of regional cerebral blood flow with H2 15O-PET and its application to AVF

Purpose It is generally assumed that vascular tracer activity is negligible in the quantification of regional cerebral blood flow (rCBF) with H₂¹⁵O and positron emission tomography (PET) under normal conditions. We attempted to surpass the assumption of abnormal vascular conditions where the vascular tracer activity is significant by introducing the vascular component into the model. Materials and methods H₂¹⁵O-dynamic and C¹⁵O PET scans were performed in an arteriovenous fistula (AVF) patient. Time–activity curves of regions of interest (ROIs) were analyzed with nonlinear least-square approximation to estimate the rCBF and fractional arterial blood volume (v_a) simultaneously with the proposed model and the standard model. Results The proposed model curve showed a fit to the time–activity curve of H₂¹⁵O at an ROI containing an enlarged vascular space induced by the AVF. The relation between the estimated v_a and CBV obtained with C¹⁵O-PET revealed that the ratio of v_a to CBV was approximately 0.23. The estimated rCBF with the proposed model in nonlesion ROIs corresponded to those of the standard model, with the estimated V_d 0.94 ml/ml. Conclusion The results supported the hypothesis that the blood volume-corrected model is applicable to the quantification of rCBF in a region with abnormal vascular structure. Furthermore, one of the advantages of the model is the feasibility of simultaneous estimation of the rCBF and arterial blood volume with dynamic-H₂¹⁵O PET scans.