BOLD MRI MONITORING OF CHANGES IN CEREBRAL PERFUSION INDUCED BY ACETAZOLAMIDE AND HYPERCARBIA IN THE RAT

To evaluate MRI methods for estimating cerebrovascular reserve, we computed changes in the R(2)* and R(2) transverse relaxation rate and apparent diffusion coefficient (ADC) at 2.0 Testa in five rats after administration of 30 mg of acetazolamide and in four rats during inhalation of 20% carbon dioxide gas. Significant decreases in R(2)*, corresponding to increases in gradient echo MRI signals, occurred in both the acetazolamide (average change -8.3%, P = 0.005) and the carbon dioxide (-2.7%, P = 0.009) treated animals. The computed Values for R(2) and ADC were unchanged. The magnitude of the gradient echo MRI changes observed should permit anatomic mapping of blood flow reactivity patterns in normal human subjects and In patients at risk for cerebrovascular disease.