Related Experiment Video
Updated: Jul 7, 2026
Brain Infarct Segmentation and Registration on MRI or CT for Lesion-symptom Mapping
Published on: September 25, 2019
Interexaminer difference in infarct volume measurements on MRI: a source of variance in stroke research
Hakan Ay1, E Murat Arsava, Mark Vangel
1Stroke Service, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, 149 13th Street, Room 2301, Charlestown MA 02129, USA. hay@partners.org
Background And Purpose:
The measurement of ischemic lesion volume on diffusion- (DWI) and perfusion-weighted MRI (PWI) is examiner dependent. We sought to quantify the variance imposed by measurement error in DWI and PWI lesion volume measurements in ischemic stroke.
Methods:
Fifty-eight consecutive patients with DWI and PWI within 12 hours of symptom onset and follow-up MRI on >or= day-5 were studied. Two radiologists blinded to each other measured lesion volumes by manual outlining on each image. Interexaminer reliability was evaluated by intraclass correlation coefficients (ICC) and relative paired difference or RPD (ratio of difference between 2 measurements to their mean). The ratio of between-examiner variability to between-subject variability (variance ratio) was calculated for each imaging parameter.
Results:
The correlation (ICC) between examiners ranged from 0.93 to 0.99. The median RPD was 10.0% for DWI, 14.1% for mean transit time, 18.9% for cerebral blood flow, 21.0% for cerebral blood volume, 16.8% for DWI/MTT mismatch, and 6.3% for chronic T2-weighted images. There was negative correlation between RPD and lesion volume in all but chronic T2-weighted images. The variance ratio ranged between 0.02 and 0.10.
Conclusions:
Despite high correlation between volume measurements of abnormal regions on DWI and PWI by different examiners, substantial differences in individual measurements can still occur. The magnitude of variance from measurement error is primarily determined by the type of imaging and lesion volume. Minimizing this source of variance will better enable imaging to deliver on its promise of smaller sample size.
Insights
Measurement variability in diffusion- (DWI) and perfusion-weighted MRI (PWI) for ischemic stroke exists despite high correlations. Lesion volume and imaging type influence measurement error, impacting clinical trial sample sizes.
Area of Science:
- Neurology
- Radiology
- Medical Imaging
Background:
- Ischemic stroke lesion volume measurement using diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) is subject to examiner dependency.
- Quantifying this measurement error is crucial for accurate clinical assessments and research.
Purpose of the Study:
- To quantify the variance introduced by measurement error in DWI and PWI lesion volume assessments in ischemic stroke patients.
- To evaluate inter-examiner reliability in lesion volume measurements.
Main Methods:
- Fifty-eight ischemic stroke patients with DWI and PWI within 12 hours of symptom onset were studied.
- Two blinded radiologists manually outlined lesion volumes on DWI, PWI (mean transit time, cerebral blood flow, cerebral blood volume), DWI/MTT mismatch, and chronic T2-weighted images.
- Inter-examiner reliability was assessed using intraclass correlation coefficients (ICC) and relative paired difference (RPD).
Main Results:
- High inter-examiner correlations (ICC: 0.93–0.99) were observed for DWI and PWI measurements.
- Median RPD varied by imaging parameter, with DWI at 10.0% and cerebral blood volume at 21.0%.
- Variance ratio ranged from 0.02 to 0.10, indicating measurement error is primarily influenced by imaging type and lesion volume.
Conclusions:
- Substantial differences in individual lesion volume measurements can occur despite high inter-examiner correlations.
- The extent of variance from measurement error depends on the specific imaging technique and the size of the ischemic lesion.
- Reducing measurement variance is essential for optimizing imaging's role in enabling smaller clinical trial sample sizes.
