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Quantitative evaluation of microvascular density after stroke in rats using MRI
Asamoah Bosomtwi1, Quan Jiang, Guang L Ding
1Department of Neurology, Henry Ford Hospital, Detroit, Michigan 48202, USA.
Abstract:
We investigated vascular changes after stroke using magnetic resonance imaging (MRI) microvascular density (MVD) measurement. T(2) and T(2)(*) were measured in eight rats before and after injecting an intravascular superparamagnetic iron oxide contrast agent to derive the corresponding transverse relaxation shift. Reliability of MRI for measurement of MVD was compared with corresponding sections immunostained with von Willebrand factor (vWF) 2 weeks after stroke. The intracorrelation coefficient (ICC) and its 95% lower bound (LB) was high in the ischemic recovery region (ICC=0.753), moderate in the contralateral area of normal brain tissue (ICC=0.70), and low in the ischemic core (ICC=0.24). A very good agreement (ICC=0.85) and correlation (r=0.90) were observed using only the recovery region and normal contralateral hemisphere (ICC=0.85; 95% LB=0.78; P<0.05). The mean MRI MVD in the center of the core lesion (26+/-9 per mm(2)) was lower than in the recovery region (209+/-60 per mm(2)) or contralateral normal hemisphere (313+/-32 per mm(2)). However, large errors in MRI MVD were encountered in the ischemic core. Our data demonstrate that MRI MVD measurements can quantitatively evaluate microvascular changes in the brain tissue after stroke, if the MVD is not extremely low as in the ischemic core.
Insights
Magnetic resonance imaging (MRI) can measure microvascular density (MVD) after stroke. MRI reliably assesses MVD in recovery areas, but not in the ischemic core.
Area of Science:
- Neuroscience
- Radiology
- Biomedical Engineering
Background:
- Stroke significantly impacts brain microvasculature.
- Accurate measurement of microvascular density (MVD) is crucial for understanding stroke recovery.
- Magnetic resonance imaging (MRI) offers a non-invasive method for assessing MVD.
Purpose of the Study:
- To evaluate the reliability of MRI for measuring microvascular density (MVD) in rat brains following induced stroke.
- To compare MRI-derived MVD measurements with immunohistochemical staining (von Willebrand factor).
- To determine the accuracy of MRI MVD in different brain regions: ischemic core, recovery zone, and contralateral hemisphere.
Main Methods:
- Eight rats underwent MRI T(2) and T(2)(*) measurements before and after injecting a superparamagnetic iron oxide contrast agent.
- Transverse relaxation shifts were calculated to derive MVD.
- Post-stroke brain sections were immunostained for von Willebrand factor (vWF) for comparison.
- Intraclass correlation coefficients (ICC) and Pearson correlation (r) were used to assess reliability and agreement.
Main Results:
- High reliability (ICC=0.753) was found for MVD measurement in the ischemic recovery region.
- Moderate reliability (ICC=0.70) was observed in the contralateral normal brain tissue.
- Low reliability (ICC=0.24) was noted in the ischemic core.
- Excellent agreement (ICC=0.85, r=0.90) was achieved when analyzing only the recovery and contralateral regions.
- Mean MRI MVD was significantly lower in the ischemic core (26±9/mm²) compared to the recovery region (209±60/mm²) and contralateral hemisphere (313±32/mm²).
Conclusions:
- MRI-based MVD measurement is a reliable quantitative tool for assessing microvascular changes post-stroke in brain regions with sufficient vascularity.
- MRI MVD is highly accurate in the ischemic recovery region and contralateral hemisphere.
- MRI MVD measurements are unreliable in the ischemic core due to extremely low microvascular density.
