Abstract
Lesion expansion in the week after acute stroke involves both infarct growth (IG) and anatomic distortion (AD) because of edema and hemorrhage. Enabling separate quantification would allow clinical trials targeting these distinct pathological processes. We developed an objective and automated approach to quantify these processes at 24 hours and 1 week. Patients with acute ischemic stroke were scanned at presentation, 24 hours, and 1 week in a magnetic resonance imaging (MRI) cohort study. IG and AD were calculated from follow-up lesion masks after linear and nonlinear registration to a presenting MRI scan. Performance of IG and AD was compared with edema quantified using cerebrospinal fluid displacement. The use of alternative reference images to define AD, including template MRI, mirrored MRI, and presenting computed tomographic scan, was explored. Thirty-seven patients with nonlacunar stroke were included. AD was responsible for 20% and 36% of lesion expansion at 24 hours (n=30) and 1 week (n=28). Registration-defined IG and AD compared favorably with edema quantified using cerebrospinal fluid displacement, particularly at smaller infarct volumes. Presenting computed tomographic imaging was the preferred alternative reference image to presenting MRI for measuring AD. The contributions of IG and AD to lesion expansion can be measured separately over time through the use of image registration. This approach can be used to combine imaging outcome data from computed tomography and MRI.
Highlights
Background and PurposeLesion expansion in the week after acute stroke involves both infarct growth (IG) and anatomic distortion (AD) because of edema and hemorrhage
Lesion expansion after the ischemic insult is because of a combination of infarct growth (IG), which is associated with poor long-term clinical outcomes[3,4] and anatomic distortion (AD) because of cerebral edema and hemorrhagic transformation—the major cause of neurological deterioration and death in the days after the event.[5,6,7]
The most common approaches to defining IG in trials have used either differences in measured infarct volumes between time points or the identification of regions of new infarction after linear image registration.[8,9]
Summary
Patients with acute ischemic stroke were scanned at presentation, 24 hours, and 1 week in a magnetic resonance imaging (MRI) cohort study. Patients aged >18 years with nonlacunar ischemic stroke were recruited within 18 hours of symptom onset into a prospective observational imaging cohort study under research protocols agreed by the UK National Research Ethics Service committee (ref 12/SC/0292 and 13/SC/0362) and by the local institutional review board. Inclusion criteria were nonlacunar ischemic stroke and unilateral infarct visible on follow-up imaging at 24 hours, at 1 week, or both. Patients with a contraindication to MRI or impaired conscious level at presentation (score >1 on question 1a of the National Institutes for Health Stroke Scale) were not included. National Institutes for Health Stroke Scale was performed at the time of each scan. Six healthy volunteers were recruited and imaged under an agreed technical development protocol approved by the institution’s research governance office
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