MR Study On The Mechanism Of Hypertension Related Cerebral Small Vessel Disease And Its Clinical Evaluation

Part Ⅰ Study on normal-appearing white matter perfusion of mild to moderate hypertension using 3D pseudo-continuous arterial spin labelingBackground and Purpose White matter (WM) is the particularly relevant and potentially indicative area of cerebral small vessel disease (CSVD) in hypertensive patients. It was hypothesized that abnormal cerebral blood flow (CBF) in WM appeared at early stage of hypertension; hence, our objective was to investigate the hemodynamic changes of normal-appearing white matter (NAWM) in hypertension, using 3D pseudo-continuous arterial spin labeling (3D pCASL) technique.Materials and Methods Seventy-three subjects, including a patient group (n=41; 30 males; age=47.7±8.3 years; test-time blood pressure (BP)=155±23/98±11mmHg) and an age-matched control group (n=32; 14 males; age=46±8.3 years; test-time BP=117±8/76±10 mmHg), were recruited and scanned on a 3.0T MRI system using T2 FLAIR,3D FSPGR and 3D pCASL sequences. The CBF values in NAWM (bilateral centrum semiovale, anterior and posterior horns of periventricular WM, genu and splenium of corpus callosum (CC)), gray matter, cingulate gyrus, amygdala, pallidum, putamen and thalamus were extracted. Unpaired t test and one-way ANOVA were performed to evaluate the significance of the inter-group difference in CBF modifications.Results Compared to healthy volunteers, CBF values in global GM (P=0.005), centrum semiovale (R:P=0.000, L:P=0.000), anterior horns of periventricular WM (R: P=0.002, L:P=0.001), posterior horns of periventricular WM (R:P=0.000, L: P=0.000) and splenium of CC (P=0.003) were found to be lower in hypertensive patients, except for genu of CC, cingulate gyrus, amygdala, pallidum, putamen and thalamus (P>0.05). Furthermore, compared to control group, mild hypertensive patients showed significantly reduced CBF in centrum semiovale (R:P=0.011, L:P=0.011), L anterior horn of periventricular WM(L:P=0.048), posterior horns of periventricular WM(R:P=0.002, L:P=0.01) and splenium of CC (P=0.021), but no inter-group differences in GM, R anterior horn of periventricular WM, genu of CC (P>0.05), while moderate hypertension showed significantly reduced CBF in all ROIs (P<0.05). However, it was observed that, between mild and moderate hypertensive patients, there was no statistically significant difference in CBF values except for genu of CC (P<0.05).Conclusion 3D pCASL has the ability to detect subtle WM hemodynamic abnormalities even at the early stage of hypertension, even when these WM regions appeared normal in conventional MR images. Furthermore, the observed reduction in CBF clustered in several specific WM regions of hypertensive subjects, indicating a potential risk of cerebral small vessel complications, as a result it could serve as an early imaging marker of hypertension-related CSVD.Part Ⅱ Comparative study on susceptibility of 3D pCASL and DTI on normal-appearing white matter changes in patients with hypertensionBackground and Purpose The identification of imaging biomarkers of hypertension is urgent for its early diagnosis. It was known that noninvasive and accurate quantification of regional cerebral blood perfusion and fractional anisotropy (FA) can study the subtle changes in white matter blood flow and microstructure. Our objective was to compare the susceptibility of 3D pseudo-continuous arterial spin labeling (3D pCASL) and diffusion tensor imaging (DTI) techniques in detecting WM changes in hypertensive patients.Materials and Methods Sixty-three subjects including a hypertensive group (n,31; male,24; age,48.4±8.2 years, test-time BP,153±25/96±12mmHg) and an age-matched control group (n,32; male,14; age,46±8.3 years; test-time BP,117±8/76±10 mmHg), were recruited and scanned using 3D pCASL and DTI sequences on 3.0T MR. The CBF data were manually obtained from bilateral centrum semiovale, periventricular WM and genu and splenium of corpus callosum (CC), DTI data were calculated from the similar location including bilateral superior, anterior and posterior corona radiate with FSL. Unpared t-test was performed to compare the significance of the inter-group difference in CBF and FA modifications.Results Compare to healthy volunteers, CBF values were reduced in various WM regions (P<0.05) except for genu of CC (P>0.05), whereas FA values were only declined in the similar location of bilateral anterior corona radiate (P<0.05), but also tended to be decreased in bilateral superior and posterior corona radiate, although those results were not statistically significant.Conclusion 3D pCASL is more susceptibility to detect the WM changes at the early stage of hypertension compared to DTI technique. It can be used as an early imaging marker of hypertension-related CSVD.