Moyamoya disease is a disease in which certain arteries in the brain are constricted. Blood flow is blocked by the constriction, and also by blood clots (thrombosis). Patients with Moyamoya Disease (MMD) need the hemodynamic evaluation of vascular territories at risk of stroke.
Today’s investigative standards include H215O PET/CT with pharmacological challenges with acetazolamide (ACZ). Recent developments suggest that CO2-triggered blood‑oxygen-level-dependent (BOLD) functional MRI might provide comparable results to current standard methods for evaluation of territorial hemodynamics while being a more widely available and easily implementable method.

CO2-triggered BOLD MRI

This study examines the results of a newly developed quantifiable analysis algorithm for CO2-triggered BOLD MRI in Moyamoya patients and correlates the results with H215O PET/CT with ACZ challenge to assess comparability between both modalities. CO2-triggered BOLD MRI and to H215O PET/CT with ACZ challenge in patients with angiographically proven MMD.
Standardized fashion by visual inspection; as well as with a semi-quantitative analysis using stimuli-induced approximated regional perfusion-weighted data and BOLD-signal changes with reference to the cerebellum. 20 consecutive patients fulfilled the inclusion criteria; a total of 160 vascular territories analyzed retrospectively.

So visual analysis (4-step visual rating system) of standardized; color-coded cerebrovascular reserve/reactivity maps showed a very strong correlation (Spearman’s rho = 0.9, P < 0.001) between both modalities. Likewise, comparison of approximated regional perfusion changes across vascular territories (normalized to cerebellar change) reveals a highly significant correlation between both methods (Pearson’s r = 0.71, P < 0.001).

Hemodynamic evaluation of MMD

The present analysis indicates that CO2-triggered BOLD MRI is a very promising tool for the hemodynamic evaluation; of MMD patients with results comparable to those seen in H215O PET/CT with ACZ challenge. It, therefore, holds future potential in becoming a routine examination in the pre- and postoperative evaluation of MMD patients after further prospective evaluation.

CO2-triggered BOLD MRI has developed significantly since its first descriptions and has the potential; to become a routine tool for the evaluation of the cerebrovascular reactivity in the future. The studies performed to date have focused on the image-acquisition techniques; and their optimization as well as aim at critically comparing it with other imaging modalities.

In conclusion, MMD where the patients vary in severity of angiopathy and collateral formation; the evaluation of cerebral reserve capacity is not possible with angiography and MRI alone; hence necessitating additional hemodynamic imaging such as H215O PET with ACZ challenge. Less expensive, without the need of an intravenous injection; more widely available and easy to implement BOLD MRI may able to substitute these in the future.