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Simultaneous PET/MRI Imaging During Mouse Cerebral Hypoxia-ischemia
Published on: September 20, 2015
Penumbra detection using PWI/DWI mismatch MRI in a rat stroke model with and without comorbidity: comparison of
Emma Reid1, Delyth Graham, M Rosario Lopez-Gonzalez
1Glasgow Experimental MRI Centre, Institute of Neuroscience and Psychology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK.
Abstract:
Perfusion-diffusion (perfusion-weighted imaging (PWI)/diffusion-weighted imaging (DWI)) mismatch is used to identify penumbra in acute stroke. However, limitations in penumbra detection with mismatch are recognized, with a lack of consensus on thresholds, quantification and validation of mismatch. We determined perfusion and diffusion thresholds from final infarct in the clinically relevant spontaneously hypertensive stroke-prone (SHRSP) rat and its normotensive control strain, Wistar-Kyoto (WKY) and compared three methods for penumbra calculation. After permanent middle cerebral artery occlusion (MCAO) (WKY n=12, SHRSP n=15), diffusion-weighted (DWI) and perfusion-weighted (PWI) images were obtained for 4 hours post stroke and final infarct determined at 24 hours on T(2) scans. The PWI/DWI mismatch was calculated from volumetric assessment (perfusion deficit volume minus apparent diffusion coefficient (ADC)-defined lesion volume) or spatial assessment of mismatch area on each coronal slice. The ADC-derived lesion growth provided the third, retrospective measure of penumbra. At 1 hour after MCAO, volumetric mismatch detected smaller volumes of penumbra in both strains (SHRSP: 31 ± 50 mm(3), WKY: 22 ± 59 mm(3), mean ± s.d.) compared with spatial assessment (SHRSP: 36 ± 15 mm(3), WKY: 43 ± 43 mm(3)) and ADC lesion expansion (SHRSP: 41 ± 45 mm(3), WKY: 65 ± 41 mm(3)), although these differences were not statistically significant. Spatial assessment appears most informative, using both diffusion and perfusion data, eliminating the influence of negative mismatch and allowing the anatomical location of penumbra to be assessed at given time points after stroke.
Insights
Perfusion-weighted imaging/diffusion-weighted imaging (PWI/DWI) mismatch helps identify penumbra in acute stroke. Spatial assessment of PWI/DWI mismatch is most informative for evaluating penumbra volume and location.
Area of Science:
- Neuroscience
- Radiology
- Biomedical Engineering
Background:
- Perfusion-weighted imaging (PWI) and diffusion-weighted imaging (DWI) are crucial for identifying the penumbra in acute stroke.
- Current methods for PWI/DWI mismatch calculation face limitations in threshold determination, quantification, and validation.
- A lack of consensus exists regarding the optimal approach for penumbra assessment using mismatch.
Purpose of the Study:
- To determine perfusion and diffusion thresholds from final infarct in spontaneously hypertensive stroke-prone (SHRSP) rats and Wistar-Kyoto (WKY) rats.
- To compare three distinct methods for calculating penumbra volume: volumetric mismatch, spatial mismatch, and apparent diffusion coefficient (ADC)-derived lesion growth.
- To evaluate the efficacy of each method in accurately assessing penumbra in an acute stroke model.
Main Methods:
- Permanent middle cerebral artery occlusion (MCAO) was induced in WKY (n=12) and SHRSP (n=15) rats.
- DWI and PWI images were acquired at 4 hours post-stroke, with final infarct volume determined at 24 hours on T2-weighted scans.
- Penumbra was calculated using volumetric mismatch (perfusion deficit volume minus ADC lesion volume), spatial mismatch assessment on each slice, and retrospective ADC lesion expansion.
Main Results:
- At 1 hour post-MCAO, volumetric mismatch underestimated penumbra volumes in both SHRSP and WKY rats compared to spatial assessment and ADC lesion expansion.
- While not statistically significant, spatial assessment demonstrated a trend towards more informative penumbra volume detection.
- Spatial assessment effectively utilizes both diffusion and perfusion data, avoids negative mismatch issues, and allows for anatomical localization of the penumbra.
Conclusions:
- Spatial assessment of PWI/DWI mismatch appears to be the most informative method for evaluating penumbra in acute stroke models.
- This method overcomes limitations of volumetric approaches by incorporating anatomical location and avoiding negative mismatch.
- Further validation is warranted, but spatial assessment offers a promising approach for accurate penumbra quantification and characterization in stroke research.
