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Diffusion-weighted arterial spin labeling MRI to investigate mannitol-induced blood brain barrier disruption
Yash Vardhan Tiwari1, Eric R Muir2, Zhao Jiang3
1Department of Radiology, Albert Einstein College of Medicine and Montefiore Medical Center, Bronx, NY, USA.
Purpose:
Diffusion-weighted arterial spin labeling (DW-ASL) MRI has been proposed to determine the rate of water exchange (Kw) across the blood brain barrier (BBB). This study aims to further evaluate Kw MRI by comparing it with standard dynamic contrast-enhanced (DCE) MRI and histology in association with mannitol-induced disruption of the BBB.
Methods:
DW-ASL was measured using a multiple b-value MRI protocol in normal rats at three post-labeling delays (N = 19), before and after intra-carotid injection of mannitol to disrupt BBB in one hemisphere (N = 13). An approach using only two b-values to detect mannitol-induced changes was also tested. DCE MRI and Evans blue histology were performed on the same animals. Quantitative analysis and pixel-by-pixel correlation were performed amongst Kw, DCE MRI and Evans blue histology.
Results:
Kw in the grey matter in the normal rat brain was 252 ± 38 min-1 (±standard error of the mean). The two b-value approach provided reasonable approximation of multiple-b DW-ASL parameters, reducing acquisition time. Kw is sensitive to mannitol-induced changes in BBB permeability and was reduced to 89 ± 17 min-1 in the affected hemisphere compared to 191 ± 22 min-1 in the unaffected hemisphere (P < 0.05). Regions with abnormality in Kw maps were in general agreement with DCE and Evans blue maps, although there are some distinct differences in location and the change in values.
Conclusion:
Kw is sensitive to mannitol-induced changes in the BBB, with BBB disruption confirmed by DCE MRI and Evans blue histology.
Insights
Diffusion-weighted arterial spin labeling (DW-ASL) MRI measures water exchange (Kw) across the blood-brain barrier (BBB). This study shows Kw MRI effectively detects BBB disruption, correlating with other imaging methods.
Area of Science:
- Neuroimaging
- Biophysics
Background:
- The blood-brain barrier (BBB) regulates substance passage into the brain.
- Diffusion-weighted arterial spin labeling (DW-ASL) MRI is a non-invasive technique to assess BBB water exchange rate (Kw).
Purpose of the Study:
- To evaluate the efficacy of Kw MRI in detecting mannitol-induced BBB disruption.
- To compare Kw MRI findings with dynamic contrast-enhanced (DCE) MRI and Evans blue histology.
Main Methods:
- DW-ASL MRI was performed on rats using multiple b-values before and after mannitol infusion to disrupt the BBB.
- A simplified two b-value approach was tested for faster acquisition.
- DCE MRI and Evans blue histology were used for comparative analysis.
Main Results:
- Normal Kw in rat grey matter was 252 ± 38 min⁻¹.
- The two b-value approach approximated multi-b-value DW-ASL parameters.
- Mannitol-induced BBB disruption significantly reduced Kw (89 ± 17 min⁻¹ vs. 191 ± 22 min⁻¹), confirmed by DCE MRI and histology.
Conclusions:
- Kw MRI is sensitive to BBB permeability changes.
- DW-ASL provides a viable method for assessing BBB integrity, comparable to DCE MRI and histology.
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