Natural Brain Tissue Pulsatility measurement: A pilot study in older depressed patients

It was shown that natural brain displacement is composed of a cardiac component of low amplitude and short duration and a slower respiratory component with high-amplitude. During the systolic phase, the cardiac component consists of a rapid displacement followed by a slow return to the initial configuration during diastole. Tissue Pulsatility Imaging (TPI) is a new ultrasound technique used to assess natural brain tissue displacement. The aim of this study was to use TPI technique to find a potential correlation between Brain Tissue Pulsatility (BTP) and elderly depression in patients with cardiovascular risk factors. In fact, there are growing evidences that depression in the elderly is associated with cerebrovascular abnormalities. BTP of depressed and non depressed diabetic patients was compared. 25 diabetic patients were then recruited and underwent a clinical examination by a psychiatric. They were classified into two groups. A group of 11 diabetic depressed patients diagnosed (mean age 62±7 years) and a group of 14 diabetic patients without depressive symptoms (mean age 66±7 years). Ultrasound (US) recordings were realized using a medical US Siemens Scanner (Antares). Transcranial acquisitions were performed with a 2 MHz phased array probe through the right temporal bone window. A direct access to the beamformed radiofrequency (RF) signals is allowed by a User's Interface Research mode installed on the Scanner. The acquisition of six cardiac cycles was realized on each patient with 25 frames/s. Off-line estimation of displacements was performed by 1D correlation methods on the RF lines of the collected 2D data. With this configuration, the measured displacements correspond to the medial component (on the ultrasound beam axis) of the total displacement. Displacement was then filtered around the cardiac frequency to remove the respiratory component. The displacement was found to be greater around wall arteries and diminish away from them. It results probably from arteries pulsations and its magnitude is linked to their properties (distensibility and compliance). A significant decrease in BTP magnitude was observed in the group of depressed patients (45±7 µm) compared to the group of non depressed patients (70±15 µm).