Title : Quantitative analysis of 7.04T magnetic resonance images in the formation of white matter lesion in chronic hypertensive model rat
The preclinical diagnosis of hypertensive cerebral vascular dementia (CVD) is important in an aging society. Cerebral white matter lesions (CWMLs) accompanied by hypertension are often visualized by magnetic resonance imaging (MRI) in the early stage, but after the onset of cognitive dysfunction. For an earlier diagnosis and the prevention of CVD, we aimed to detect white matter changes earlier than those conventional identified by MRI. To address this issue, we quantitatively analyzed MR images using Deoxycorticosterone acetate (DOCA)-salt-treated male rats. One week after hemi-nephrectomy, the rats were randomly divided into two groups: DOCA-salt-treated rats received a weekly subcutaneous injection of DOCA (40 mg/kg) and 1% NaCl in drinking water; Control rats received a weekly subcutaneous injection of vehicle and tap water (n=3 in each). Systolic blood pressure (sBP) was measured in a conscious rat by the tail-cuff method. After 0, 2, 3, or 4 weeks (n=3 for each group) of DOCA-salt treatment and control, all rats were subjected to 7.04T MRI under anesthesia. T2-weighted images (T2WI) were acquired using the following parameters: fast spin echo sequence, echo time = 50 ms, repetition time = 2000 ms, field of view = 2.5×2.5 cm2, matrix = 512×512 with zero-filling, and slice thickness 1 mm. MR images were quantified based on their signal to noise ratio (SNR) using aerial-noise method. After MRI, brain tissue was subjected to histochemical study. Our results indicated that sBP was gradually increased after DOCA treatment and the mean value of the SNR of DOCA-salt-treated rats also increased over time. It is of note that a significant increase of SNR was observed in the DOCA-salt-treated rats at 2 weeks (DOCA-2W), when CWMLs and état criblé had yet to be observed. Histochemical changes including CWMLs, hemorrhage, and vascular impairment were clearly observed in DOCA-3W and -4W. Taken together, these results suggest that quantitative analysis of T2WI can detect preclinical vascular changes. Now, we perform cell biological study to understand the mechanisms for CWML formation.
Audience take away:
- Deoxycorticosterone acetate (DOCA)-salt-treated rats were used to detect early hypertensive white matter changes.
- Quantification of T2WI on 7.04T MRI by aerial-noise method could detect signal elevation prior to white matter hyperintensity or état criblé.
- Applying our finding to clinical use may improve preclinical diagnosis of hypertensive vascular dementia.