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FIG 4. Example of a false-negative result. The same color scale is used to display quantitative rCBF images calculated by using the IMP autoradiographic method at the resting state and with the acetazolamide challenge. This patient had a symptomatic occluded ICA on the left side. After the administration of acetazolamide, the patient’s blood flow in the MCA territory increased only by 2.1 mL/100 g/min on the left side (%Hem = 6.0%) and by 3.1 mL/100 g/min on the contralateral side (%Hem = 8.9%). As asymmetry was absent, the use of rCBF ratios (AIHem change = -2.7) would fail to identify a bilateral reduction of flow response to acetazolamide.
