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Stroke penumbra defined by an MRI-based oxygen challenge technique: 2. Validation based on the consequences of
Craig A Robertson1, Christopher McCabe, Lindsay Gallagher
1Glasgow Experimental MRI Centre, Institute of Neuroscience and Psychology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK. c.robertson.1@research.gla.ac.uk
Abstract:
Magnetic resonance imaging (MRI) with oxygen challenge (T(2)(*) OC) uses oxygen as a metabolic biotracer to define penumbral tissue based on CMRO(2) and oxygen extraction fraction. Penumbra displays a greater T(2)(*) signal change during OC than surrounding tissue. Since timely restoration of cerebral blood flow (CBF) should salvage penumbra, T(2)(*) OC was tested by examining the consequences of reperfusion on T(2)(*) OC-defined penumbra. Transient ischemia (109 ± 20 minutes) was induced in male Sprague-Dawley rats (n=8). Penumbra was identified on T(2)(*)-weighted MRI during OC. Ischemia and ischemic injury were identified on CBF and apparent diffusion coefficient maps, respectively. Reperfusion was induced and scans repeated. T(2) for final infarct and T(2)(*) OC were run on day 7. T(2)(*) signal increase to OC was 3.4% in contralateral cortex and caudate nucleus and was unaffected by reperfusion. In OC-defined penumbra, T(2)(*) signal increased by 8.4% ± 4.1% during ischemia and returned to 3.25% ± 0.8% following reperfusion. Ischemic core T(2)(*) signal increase was 0.39% ± 0.47% during ischemia and 0.84% ± 1.8% on reperfusion. Penumbral CBF increased from 41.94 ± 13 to 116.5 ± 25 mL per 100 g per minute on reperfusion. On day 7, OC-defined penumbra gave a normal OC response and was located outside the infarct. T(2)(*) OC-defined penumbra recovered when CBF was restored, providing further validation of the utility of T(2)(*) OC for acute stroke management.
Insights
Magnetic resonance imaging with oxygen challenge (T(2)(*) OC) identifies penumbra, the brain tissue at risk during stroke. Restoring blood flow successfully salvaged this penumbra, validating T(2)(*) OC for acute stroke management.
Area of Science:
- Neuroimaging
- Stroke Research
- Biophysics
Background:
- Magnetic resonance imaging with oxygen challenge (T(2)(*) OC) utilizes oxygen as a metabolic biotracer.
- Penumbra, the tissue at risk during stroke, exhibits a distinct T(2)(*) signal change during oxygen challenge compared to surrounding tissue.
- Timely restoration of cerebral blood flow (CBF) is crucial for salvaging penumbral tissue.
Purpose of the Study:
- To investigate the consequences of reperfusion on T(2)(*) OC-defined penumbra.
- To validate the utility of T(2)(*) OC for acute stroke management by assessing penumbra recovery after blood flow restoration.
Main Methods:
- Transient ischemia was induced in male Sprague-Dawley rats.
- Penumbra was identified using T(2)(*)-weighted MRI during oxygen challenge (OC).
- Cerebral blood flow (CBF) and apparent diffusion coefficient maps were used to identify ischemia and ischemic injury, respectively. Scans were repeated after reperfusion, with final infarct and T(2)(*) OC assessments on day 7.
Main Results:
- In OC-defined penumbra, the T(2)(*) signal increase during ischemia (8.4% ± 4.1%) returned to baseline levels (3.25% ± 0.8%) after reperfusion, indicating recovery.
- Reperfusion significantly increased penumbral CBF (from 41.94 ± 13 to 116.5 ± 25 mL per 100 g per minute).
- On day 7, the OC-defined penumbra was located outside the infarct and showed a normal OC response, while the ischemic core showed minimal T(2)(*) signal change.
Conclusions:
- T(2)(*) OC-defined penumbra recovered when cerebral blood flow was restored.
- The findings provide further validation for the use of T(2)(*) OC in acute stroke management.
- This technique aids in identifying salvageable brain tissue during stroke.
