Kuniaki Ogasawara

In the clinical setting, cerebrovascular reactivity (CVR) to acetazolamide (ACZ) is measured using perfusion SPECT and perfusion CT or MRI. However, the timing of scanning for the measurement of perfusion parameters after ACZ administration varies among these modalities, and the optimal timing in patients with major cerebral arterial steno-occlusive disease remains unknown. Quantitative susceptibility mapping (QSM) can quantify the magnetic susceptibility of venous structures and brain parenchyma from T2*-weighted magnitude/phase images. The scan time for this mapping using a 7T scanner is relatively short (3 minutes 25 seconds), and this mapping may enable imaging of dynamic changes in blood oxygenation levels in venous structures and brain parenchyma. If ACZ does not influence cerebral oxygen metabolism, changes of susceptibility on QSM theoretically could indicate those of CBF. Therefore, we determined how susceptibility on 7T MR QSM dynamically changes after ACZ administration, and how such dynamic changes correlate with cerebral hemodynamics in patients with major cerebral artery steno-occlusive disease.

In patients with chronic symptomatic occlusion of the major cerebral artery, reduced CVR to ACZ in the affected cerebral hemisphere indicates a high risk of stroke recurrence. A preoperative decrease in CVR to ACZ in the cerebral hemisphere ipsilateral to carotid endarterectomy or carotid artery stenting has also been identified as a powerful predictor of postoperative cerebral hyperperfusion. Our finding that CBF change at 5 minutes after ACZ administration mostly correlates with cerebral hemodynamics suggests that CBF change at 5 minutes after ACZ administration may predict the risk of cerebrovascular adverse events more accurately than conventional methods of ACZ administration. In addition, the examination time of the present method using 7T MR QSM was <12 minutes.

We currently prospectively collect data to determine whether CBF change at 5 minutes after ACZ administration may predict the risk of cerebrovascular adverse events more accurately than conventional methods of ACZ administration using 7T MR QSM. We also will present these data in the academic journals in the near future.

Read this article at AJNR.org …