Prediction of Hemorrhage in Acute Ischemic Stroke Using Permeability MR Imaging
Andrea Kassnera,
Timothy Robertsa,
Keri Taylorb,
Frank Silverc and
David Mikulisb
a Department of Medical Imaging, University of Toronto & UHN (Princess Margaret Hospital), Toronto, Ontario, Canada
b Department of Medical Imaging, The Toronto Western Hospital, Toronto, Ontario, Canada
c Department of Neurology, The Toronto Western Hospital, Toronto, Ontario, Canada
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FIG 1. (A–C): Three patients experienced HT. Images from all 3 are shown from the initial MR imaging at presentation (upper left: DWI; upper middle: permeability map; upper right: dynamic enhancement time course; lower left: post-Gd T1 SE) and from follow-up scans after 24–72 hours (lower middle: 3D-GRE-MR imaging; lower right: CT). Progressive signal intensity increase on serial T1-weighted images demonstrates a clear positive increasing slope (upper right), and a corresponding hyperintensity on a pixel-by-pixel map of microvascular permeability (yellow arrows). In only 1 case (A) is enhancement clearly visible on the T1-weighted SE (white arrows). Follow-up CT shows hyperintensity characteristic of HT in the same area (orange arrows), but this appearance varies from subtle to frank; hemorrhage is additionally depicted on gradient recalled echo MR imaging (orange arrows). In Fig 1B, follow-up CT was performed 1 day after the follow-up MR imaging. The top arrow shows subtle evidence of hemorrhage corresponding to 3D-GRE-MR imaging; the bottom arrow shows new hemorrhage that must have developed after the follow-up MR imaging and that corresponds to the permeability abnormality on the initial MR imaging.
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FIG 2. A representative patient presenting with AIS (<24 hours), visible as hyperintensity on DWI (upper left). Lack of progressive signal intensity increase on serial T1-weighted images WIs is shown as a negligible slope of enhancement (upper right), and no corresponding hyperintensity on a pixel-by-pixel map of microvascular permeability (lower left). In this case, the permeability value in the hyperintense region was –0.14 mL/100 g/min. Follow-up CT (48 hours later) showed no evidence of HT (lower right).
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FIG 3. Mean microvascular permeability values obtained at MR imaging at time of presentation in the lesion and contralateral (normal) hemisphere of patients who subsequently proceeded to HT (left) and those who did not proceed to HT (right). Significantly elevated permeability values are seen only in the lesion of patients who subsequently proceed to HT.
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