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Apparent diffusion coefficient threshold for delineation of ischemic core
Archana Purushotham1, Bruce C V Campbell, Matus Straka
1Department of Neurology and Neurological Sciences, the Stanford Stroke Center, Stanford University Medical Center, Stanford, CA, USA; Institute for Stem Cell Biology and Regenerative Medicine, National Center for Biological Sciences, Bangalore, India.
Background:
MRI-based selection of patients for acute stroke interventions requires rapid accurate estimation of the infarct core on diffusion-weighted MRI. Typically used manual methods to delineate restricted diffusion lesions are subjective and time consuming. These limitations would be overcome by a fully automated method that can rapidly and objectively delineate the ischemic core. An automated method would require predefined criteria to identify the ischemic core.
Aim:
The aim of this study is to determine apparent diffusion coefficient-based criteria that can be implemented in a fully automated software solution for identification of the ischemic core.
Methods:
Imaging data from patients enrolled in the Diffusion and Perfusion Imaging Evaluation for Understanding Stroke Evolution (DEFUSE) study who had early revascularization following intravenous thrombolysis were included. The patients' baseline restricted diffusion and 30-day T2 -weighted fluid-attenuated inversion recovery lesions were manually delineated after coregistration. Parts of the restricted diffusion lesion that corresponded with 30-day infarct were considered ischemic core, whereas parts that corresponded with normal brain parenchyma at 30 days were considered noncore. The optimal apparent diffusion coefficient threshold to discriminate core from noncore voxels was determined by voxel-based receiver operating characteristics analysis using the Youden index.
Results:
51,045 diffusion positive voxels from 14 patients who met eligibility criteria were analyzed. The mean DWI lesion volume was 24 (± 23) ml. Of this, 18 (± 22) ml was ischemic core and 3 (± 5) ml was noncore. The remainder corresponded to preexisting gliosis, cerebrospinal fluid, or was lost to postinfarct atrophy. The apparent diffusion coefficient of core was lower than that of noncore voxels (P < 0.0001). The optimal threshold for identification of ischemic core was an apparent diffusion coefficient ≤ 620 × 10(-6) mm(2) /s (sensitivity 69% and specificity 78%).
Conclusions:
Our data suggest that the ischemic core can be identified with an absolute apparent diffusion coefficient threshold. This threshold can be implemented in image analysis software for fully automated segmentation of the ischemic core.
Insights
Automated software can now rapidly identify the ischemic core in stroke patients using an apparent diffusion coefficient threshold. This improves acute stroke intervention selection by providing objective and quick infarct core estimation.
Area of Science:
- Neuroimaging
- Radiology
- Stroke Imaging
Background:
- Accurate infarct core estimation on diffusion-weighted MRI is crucial for acute stroke intervention selection.
- Manual delineation of restricted diffusion lesions is time-consuming and subjective.
- Automated methods are needed for rapid and objective ischemic core identification.
Purpose of the Study:
- To determine apparent diffusion coefficient (ADC) criteria for automated ischemic core identification.
- To develop criteria for a fully automated software solution for infarct core segmentation.
Main Methods:
- Analysis of diffusion-weighted MRI data from the DEFUSE study.
- Manual delineation of restricted diffusion and 30-day infarct lesions.
- Voxel-based receiver operating characteristics analysis to determine the optimal ADC threshold.
Main Results:
- An apparent diffusion coefficient threshold of ≤ 620 × 10(-6) mm(2)/s identified the ischemic core with 69% sensitivity and 78% specificity.
- Core voxels exhibited significantly lower ADC values than noncore voxels (P < 0.0001).
- Mean ischemic core volume was 18 ml (± 22 ml).
Conclusions:
- An absolute apparent diffusion coefficient threshold can reliably identify the ischemic core.
- This threshold is suitable for implementation in image analysis software for automated segmentation.
- Automated segmentation facilitates rapid and objective infarct core estimation in acute stroke.
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