Arjen Lindenholz

24 CHAPTER 2 Ischemic stroke About 80% of strokes are ischemic and about 20% hemorrhagic in origin. Hemorrhagic transformation is a not infrequent complication of ischemic stroke and Figure 1 shows an axial 7T FLAIR image of a patient with ischemic stroke undergoing hemorrhagic transformation in the territory of the right middle cerebral artery. The figure displays the high degree of detail discernible with 7T in stroke patients. 4 Most ischemic strokes have an extracranial origin and result either from cardio-embolism or artery-to-artery embolism from the carotid or vertebrobasilar arteries. Screening for cardiac arrhythmia and evaluation of the neck vessels may point towards the correct stroke origin in most of these patients. In case of artery-to-artery embolism from the neck, luminal imaging may reveal arterial stenosis, most frequently at the level of the carotid bifurcation. Figure 1. Ultra-high resolution imaging of ischemic stroke. Axial 7T contrast-enhanced 3D-FLAIR image of 50-year-old female with a recent right-sided ischemic stroke with hemorrhagic transformation, repetition time 8000 ms, echo time 300 ms, inversion time 2200 ms, acquired voxel size 0.8 × 0.8 × 0.8 mm 3 , reconstructed voxel size 0.5 × 0.5 × 0.5 mm 3 , field-of-view 250 x 250 × 190 mm 3 , scan duration 10 minutes 48 seconds. A hyperintense border is seen to surround the lentiform nucleus (putamen and globus pallidus, arrowheads), which appears hypointense due to blood components. A smaller infarct is also seen in the insular region (black arrow), and multiple hyperintense dots are also seen along the ventricular border of the head of the caudate nucleus (white arrow), all of which are compatible with satellite infarctions.