A Novel MRA-Based Framework For Detecting Correlation Between Cerebrovascular Changes and Mean Arterial Pressure

Abstract

Systemic hypertension is a significant contributor for strokes and cognitive impairment and is a leading cause of mortality in the USA. Changes in cerebral vascular diameter and cerebral perfusion pressure have been reported to precede elevation of systemic blood pressures. A novel, non-invasive Time-of-Flight - Magnetic Resonance Angiography (TOF-MRA) based framework for detection of cerebrovascular changes is presented. The proposed framework analyzes brain TOF-MRA data to quantify changes in cerebral vascular diameter and cerebral perfusion pressure. The framework has three major steps: 1) Adaptive segmentation to extract large and small diameter cerebral vessels from TOF-MRA images using both appearance and 3-D spatial information of the vascular system; 2) Estimation of the Cumulative Distribution Function (CDF) of the 3-D distance map of the cerebral vascular system, which represents the changes in diameter of the 3-D vascular system; and 3) Statistical and correlation analysis that measured the effect of Mean Arterial Pressure (MAP) on blood vessels' diameter changes. The efficacy of the framework was evaluated using MRA images and blood pressure (BP) measurements obtained from 15 patients (M=8, F=7, Age $= 49. 2 \pm 7.3$ years) on Day 0 and Day 700. The framework had a dice similarity coefficient of 92.23%, a sensitivity of 94. 8% and a specificity of $\sim 99$% in detecting elevated vascular pressures compared to ground truth. Statistical analysis demonstrated an inverse relationship between blood vessels diameters and MAP. This correlation was valid for both upper (above the circle of Willis) and lower (circle of Willis and below) sections of the brain. The proposed methodology may be used to quantify changes in cerebral vasculature and cerebral perfusion pressure non-invasively through MRA image analysis, which may be a useful tool for clinicians to optimize medical management of pre-hypertension and hypertension.