Commentary Imaging Cerebral Blood Flow in lnterventional Neuroradiology: Choice of Technique and Indications

In this issue of the AJNR, Tarr et al. [1] present serial measurements of cerebral blood flow (CBF) obtained by using xenon CT in eight patients having staged embolization of arteriovenous malformation (AVM). Tarr et al. used administration of acetazolamide and repetition of the blood-flow study to challenge the cerebral vasculature and test for autoregulatory reserve. They obtained a baseline and a single CBF study after embolization in six patients. Two patients had more than one CBF study after embolization . The times of study were from 1 to 26 days after embolization. Twenty percent of the attempted studies (two patients) could not be completed because the patients had anxiety attacks. Analysis of data consisted of calculation of flow in 169 regions of interest 2 em in diameter. The mean CBF before embolization was 49 .9 ml/1 00 gjmin, and the mean CBF after embolization was 56.8 ml/1 00 gjmin. The authors categorized augmentation as normal if it was ::-:10% and as decreased if it was < 1 0%. This was despite a mean SD of blood-flow measurement within the region of interest of 19.1 ml/1 00 gjmin or 38% of the mean total blood flow. Using their criteria, they found that mean augmentation after embolization was significantly diminished relative to the augmentation before embolization . Seven of eight patients had one or more parenchymal areas that showed diminished augmentation of flow after embolization. The authors also noted significant differences in response to acetazolamide after embolization. These differences were based on six studies obtained between days 1 and 5 after embolization (two of them in the same patient), two studies in one patient