Arjen Lindenholz

28 CHAPTER 2 atherosclerotic-moyamoya syndrome, and vasculitic-moyamoya syndrome. 26 Although vessel wall imaging studies at 7T for moyamoya are still lacking, MPRAGE has already been found superior to TOF-MRA at 7T due to shorter scanning times and better brain coverage. 27 Incidental or silent infarction and the aging brain Apart from brain infarction presenting with stroke ( Figure 1 ), many (small) brain infarctions present with only few or non-specific clinical symptoms, or may even be clinically. 28-30 Still, these infarcts may present later on as an incidental finding on neuroimaging studies. They are associated with cognitive decline and worse physical functioning, and an increased risk of future stroke. 31-33 Traditionally, incidental cerebral infarctions include large and small cortical infarcts as well as subcortical infarcts, of which the latter includes lacunar infarcts. 34-37 Lacunar infarcts, perivascular spaces and white matter hyperintensities Due to the superior evaluation of small-caliber arteries in the brain on 7T arterial TOF-MRA ( Figure 2 ), it has been found that the number of lenticulostriate arteries supplying the basal ganglia is reduced in patients with lacunes (of presumed vascular origin) compared to age-matched controls. This finding has later been translated to 1.5T with flow-sensitive black blood MRA, suggesting that occlusion of lenticulostriate arteries underlies lacunar infarction of the basal ganglia. 5,37,38 At times, lacunes may be difficult to distinguish from enlarged perivascular spaces (PVS), although the latter do not have a T2-hyperintense rim around the fluid- filled space on T2-weighted or FLAIR imaging, unless they traverse an area of white matter hyperintensity. 37 At high resolution, a central vessel can occasionally be seen in the center of a perivascular space, which may differentiate the spaces from lacunes. 37,39 Also, optimized MRI parameters and segmentation methods have been developed for PVS at 7T, which have shown that PVS are much more abundant than previously reported in young patients. 39,40 Despite the term lacunar infarction, it has been shown that only a small proportion of lacunar infarcts progress to lacunes, 41,42 and non-cavitating lacunar infarcts often continue to resemble white matter lesions instead. 37,41 Also, in non-vascular disease such as multiple sclerosis (MS), characterizationof whitematter lesionswithhigh resolution MR imaging has shown diagnostic benefits. With the increased SNR of 7T MRI, the typical localization of MS plaques around small venules can be demonstrated. 43-45