PET evaluation of cerebral hemodynamics in occlusive cerebrovascular disease pre- and postsurgery

We studied cerebral blood flow (CBF), oxygen extraction fraction (OEF), transit time (TT) and hemodynamic reserve capacity using acetazolamide (ACZ) in both the pre- and postoperative states, and evaluated the effect of surgery on the cerebral hemodynamics. Methods: Twelve patients with a unilateral occlusive cerebral artery were studied. Among them, seven patients had extracranial-intracranial (EC-IC) bypass surgery, while the remaining five patients had carotid endarterectomies. The CBF was measured using the ¹⁵O-water bolus injection method in a resting state, 5 and 20 min after intravenous ACZ (1 g), while the OEF and TT were measured by the ¹⁵O steady state method. The values of these parameters were obtained by regions of interest set over the cerebral hemisphere on both sides, and which then were compared between the pre- and postoperative states using the paired Student's t-test. Results: The t values were 1.36 (CBF at rest), 2.97 (CBF at 5 min after intravenous ACZ), 1.40 (CBF at 20 min after intravenous ACZ), 2.00 (OEF) and -0.86 (TT) on the surgical side, and -0.16, 0.21, 0.22, -0.47 and 0.61 on the nonsurgical side, respectively. The t values of the ACZ response (% increase in CBF) were 3.07 (5 min after intravenous ACZ) and 0.72 (20 min) on the surgical side, and 1.03 and 0.90 on the nonsurgical side, respectively. A significant change was observed only in the CBF studies 5 min after intravenous ACZ. Conclusion: PET can demonstrate significant cerebral hemodynamic change after surgery, especially in CBF measurement 5 min after intravenous ACZ, and may therefore be useful for evaluating cerebral hemodynamics pre- and postsurgery.