Brain Perfusion Imaging Under Acetazolamide Challenge for Detection of Impaired Cerebrovascular Reserve Capacity: Positive Findings with 15O-Water PET in Patients with Negative 99mTc-HMPAO SPECT Findings

Cerebrovascular reserve capacity (CVRC) is an important parameter for treatment decisions in chronic cerebrovascular diseases. It can be assessed by measuring the acetazolamide-induced change in regional cerebral blood flow using SPECT with Tc-99m-labeled hexamethylpropyleneamine oxime (Tc-99m-HMPAO) or PET with O-15-water. Methods: Our database was searched for patients with moyamoya vasculopathy or atherosclerotic cerebrovascular disease who had undergone O-15-water PET after normal Tc-99m-HMPAO SPECT results with respect to CVRC. O-15-water PET was analyzed visually and quantitatively. Quantitative analysis was based on parametric CVRC maps generated by voxelwise image subtraction. Results: The search identified 18 patients (43 +/- 15 y, 12 moyamoya vasculopathy). PET revealed impaired CVRC in 8 patients (44%). Quantitative analysis confirmed the positive visual findings in O-15-water PET and the negative findings in Tc-99m-HMPAO SPECT. Conclusion: O-15-water PET enables detection of impaired CVRC in a considerable fraction of symptomatic patients with stenoocclusion and negative Tc-99m-HMPAO SPECT.