Brain Perfusion Imaging Under Acetazolamide Challenge for Detection of Impaired Cerebrovascular Reserve Capacity: Positive Findings with 15 O-Water PET in Patients with Negative 99m Tc-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 99m Tc-labeled hexamethylpropyleneamine oxime (99m Tc-HMPAO) or PET with 15 O-water. Methods: Our database was searched for patients with moyamoya vasculopathy or atherosclerotic cerebrovascular disease who had undergone 15 O-water PET after normal 99m Tc-HMPAO SPECT results with respect to CVRC. 15 O-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 15 O-water PET and the negative findings in 99m Tc-HMPAO SPECT. Conclusion: 15 O-water PET enables detection of impaired CVRC in a considerable fraction of symptomatic patients with stenoocclusion and negative 99m Tc-HMPAO SPECT.