A novel application of four-dimensional magnetic resonance angiography using an arterial spin labeling technique for noninvasive diagnosis of Moyamoya disease

Background: Noncontrast-enhanced time-resolved four-dimensional magnetic resonance angiography using an arterial spin labeling technique (ASL-4D MRA) is emerging as a next generation angiography for the management of neurovascular diseases. This study evaluated the feasibility of ASL-4D MRA for the diagnosis of Moyamoya disease (MMD) and MMD staging by using digital subtraction angiography (DSA) and time-of-flight MRA (TOF MRA) as current standards.

Methods: Eleven consecutive non-operated patients who underwent DSA for the diagnosis of MMD were recruited. Two independent observers evaluated the three tests. The data were analyzed for inter-observer and inter-modality agreements on MMD stage. Nine of 22 hemispheres underwent surgical revascularization and ASL-4D MRA was repeated postoperatively.

Results: Time-resolved inflow of blood through the cerebral vessels, including moyamoya vessels, was visualized in all the 22 non-operated hemispheres. MMD stages assessed by DSA and ASL-4D MRA were completely matched in 18 hemispheres, with a significant positive correlation between these modalities (r=0.93, P<0.001). Inter-observer agreement with ASL-4D MRA (κ=0.91±0.04, P<0.001) and inter-modality agreement between ASL-4D MRA and DSA (κ=0.93±0.04, P<0.001) were both excellent. MMD stages assessed by ASL-4D MRA have also a significant positive correlation with those assessed by TOF MRA (r=0.68, P=0.004). Repeated ASL-4D MRA clearly demonstrated the bypassed arteries and changes in the dynamic flow patterns of cerebral arteries in all the nine hemispheres after surgical revascularization. Of these, postoperative focal hyperperfusion was detected by single photon emission tomography in 7 hemispheres. In five of the seven hemispheres (71%) with postoperative hyperperfusion, ASL-4D MRA demonstrated focal hyperintense signals in the bypassed arteries, although TOF MRA did not.

Conclusions: Noninvasive ASL-4D MRA is feasible for the diagnosis of MMD staging. This next generation angiography may be useful for monitoring disease evolution and treatment response in cerebral arteries after revascularization surgery in MMD.