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Updated: Mar 28, 2026
A Magnetic Resonance Imaging Protocol for Stroke Onset Time Estimation in Permanent Cerebral Ischemia
Published on: September 16, 2017
T2*-weighted fMRI time-to-peak of oxygen challenge in ischemic stroke
Qiang Shen1, Shiliang Huang2, Timothy Q Duong3
1Research Imaging Institute, University of Texas Health Science Center, San Antonio, TX, USA Department of Ophthalmology, University of Texas Health Science Center, San Antonio, TX, USA Department of Radiology, University of Texas Health Science Center, San Antonio, TX, USA shenq3@uthscsa.edu duongt@uthscsa.edu.
Abstract:
T2 (*)-weighted MRI of transient oxygen challenge (OC) showed exaggerated OC percent changes in the ischemic tissue at risk compared to normal tissue. One ambiguity is that regions with high vascular density also showed exaggerated OC percent changes. This study explored time-to-peak (TTP) of the OC percent changes to improve the utility of T2 (*)-weighted OC MRI. Experiments were performed longitudinally at 30 min, 150 min and 24 h after transient (60-min) stroke in rats. Ischemic core, normal, and mismatch tissue were classified pixel-by-pixel based on apparent diffusion coefficient and cerebral blood flow. Major findings were: (i) Delayed OC TTP was localized to and corresponded well with the perfusion-diffusion mismatch. (ii) By contrast, the exaggerated OC percent changes were less localized, with changes not only in the at-risk tissue but also in some areas of the contralesional hemisphere with venous vessel origins. (iii) The OC time-course of the mismatch tissue was biphasic, with a faster initial increase followed by a slower increase. (iv) At-risk tissue with delayed TTP and exaggerated OC was normal after reperfusion and the at-risk tissue was mostly (83 ± 18%) rescued by reperfusion as indicated by normal 24-h T2. OC TTP offers unique information toward better characterization of at-risk tissue in ischemic stroke.
Insights
Time-to-peak analysis of oxygen challenge MRI improves stroke characterization. Delayed TTP identifies at-risk tissue, aiding reperfusion rescue assessment in ischemic stroke patients.
Area of Science:
- Neuroimaging
- Ischemic Stroke Research
- Biomedical Engineering
Background:
- T2(*)-weighted MRI with oxygen challenge (OC) shows exaggerated changes in ischemic tissue.
- High vascular density regions also exhibit exaggerated OC percent changes, creating ambiguity.
- Improving the diagnostic utility of OC MRI is crucial for stroke management.
Purpose of the Study:
- To explore the time-to-peak (TTP) of OC percent changes to enhance T2(*)-weighted OC MRI for stroke characterization.
- To differentiate at-risk ischemic tissue from normal tissue and identify perfusion-diffusion mismatch.
- To assess the effectiveness of reperfusion in rescuing at-risk tissue.
Main Methods:
- Longitudinal T2(*)-weighted MRI experiments in rats at 30 min, 150 min, and 24 h post-transient stroke.
- Pixel-by-pixel classification of ischemic core, normal, and mismatch tissue using apparent diffusion coefficient and cerebral blood flow.
- Analysis of OC TTP and percent changes in different tissue types.
Main Results:
- Delayed OC TTP was localized to perfusion-diffusion mismatch regions.
- Exaggerated OC percent changes were less localized, appearing in at-risk and some normal tissues.
- Mismatch tissue showed a biphasic OC time-course.
- At-risk tissue with delayed TTP was rescued by reperfusion, indicated by normal 24-h T2.
Conclusions:
- OC TTP provides unique information for better characterization of at-risk tissue in ischemic stroke.
- Delayed TTP is a reliable marker for perfusion-diffusion mismatch.
- T2(*)-weighted OC MRI with TTP analysis can assess reperfusion effectiveness and guide stroke treatment.
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