Heterogeneity evaluation of multi-high b-value apparent diffusion coefficient on cerebral ischemia in MCAO rat

Liwei Shi; Bo Yu; Qiuyan Chen; Tianxiu Zheng; Peiqiu Xing; Dingtai Wei

doi:10.3389/fnins.2022.1048429

Heterogeneity evaluation of multi-high b-value apparent diffusion coefficient on cerebral ischemia in MCAO rat

Front Neurosci. 2022 Dec 20:16:1048429. doi: 10.3389/fnins.2022.1048429. eCollection 2022.

Authors

Liwei Shi^{1

2

3}, Bo Yu^{2

3}, Qiuyan Chen^{2

3}, Tianxiu Zheng^{2

3}, Peiqiu Xing^{2

3}, Dingtai Wei^{1

2

3}

Affiliations

¹ The Third Clinical Medical College, Fujian Medical University, Fuzhou, Fujian, China.
² Department of Radiology, Ningde Municipal Hospital of Ningde Normal University, Ningde, Fujian, China.
³ Functional and Molecular Imaging Laboratory for Cerebral Vascular Diseases, Ningde Municipal Hospital of Ningde Normal University, Ningde, Fujian, China.

Abstract

Purpose: To assess brain damage in a rat model of cerebral ischemia based on apparent diffusion coefficient (ADC) data obtained from multi-high b-values and evaluate the relationship between Aquaporin 4 (AQP4) expression and ADC.

Methods: Thirty eight male Sprague-Dawley rats were randomized into two groups: (1) sham controls (n = 6) and (2) cerebral ischemia (successful model, n = 19). All rats underwent diffusion-weighted imaging (DWI) with both standard b-values and multi-high b-values (2,500-4,500 s/mm²) using a 3.0-T device. Standard ADC (ADC_st) maps and multi-high b-value ADCs (ADC_mh) were calculated, respectively. Aquaporin 4 expression was quantified using Western blot. Relative values of ADC_st and ADC_mh, AQP4 expression were compared between the sham group and the ischemia group. Correlations between ADC values and AQP4 expression were evaluated.

Results: At 0.5 h after suture insertion, the value of ADC_mh on the lesion was obviously decreased, and there was no difference in lesion volume when compared with ADC_st. After reperfusion, besides similar regions where ADC_st values decreased, we also found additional large values on ADC_mh within the cortex of the ipsilateral side or surrounding the lesion. The lesion evolution of the large value on ADC_mh was quite different from other indicators. But the total ADC_mh values were still significantly associated with ADC_st. The AQP4 protein expression level was appreciably increased after middle cerebral artery occlusion (MCAO), but there was no correlation between AQP4 expression either with ADC_mh or ADC_st.

Conclusion: We found the large values on ADC_mh during the progression of cerebral infarction is varied, but there was no correlation between ADC_mh values and AQP4 expression. ADC_mh may indicate the heterogeneity of ischemia lesions, but the underlying pathological basis should be further explored.

Keywords: Aquaporin 4; MRI; diffusion; ischemia; rat.