Development and validation of quantitative MRI techniques for CNS tissue

点击翻译按钮获取中文摘要

Magnetic Resonance Imaging (MRI) is one of the most versatile imaging techniques for studying fundamental properties of tissue. Of particular significance are quantitative MRI techniques that can measure physical parameters, which can provide more accurate and objective way of characterizing tissue properties of interest. A number of quantitative MRI (qMRI) techniques have been successfully applied to study CNS tissue, most notably: diffusion MRI, quantitative T2 MRI, Quantitative Susceptibility Mapping (QSM), and more recently inhomogeneous Magnetization Transfer (ihMT). In the current application we propose to further develop, test and validate these qMRI techniques to allow better characterization of biophysical properties of the rodent CNS tissue. Long term objective of the proposed research programme is the development, validation and application of quantitative MRI techniques to study biophysical properties of CNS tissue in animals. Short term objectives of the proposed research are: 1. To study fundamental characteristics and limitations of inhomogeneous Magnetization Transfer (ihMT) in rodent CNS tissue. We will establish the dependence of ihMT ratio values on the temperature, T1d filtering and orientation with regards to the magnetic field, both in vivo and ex vivo. We will also study the effect of tissue fixation on ihMT measurements by studying the effect of fixation time on the ihMT ratio values. 2. To carry out a combined MWI + ihMT measurements in rat spinal cord. We will optimize a pulse sequence that combines both quantitative T2 and ihMT methods. This will allow measurement of ihMT effect separately on myelin and intra-/extra-axonal water compartments. These measurements will be carried out in normal and injured rat spinal cords both in-vivo and ex-vivo. 3. To compare MWI, QSM, diffusion MRI, and ihMT in their ability to measure myelin content and distinguish between functional myelin and myelin debris. The measurements will be carried in in normal and injured rat spinal cords, both in-vivo and ex-vivo, and the MRI results will be correlated with histology and Transmission Electron Microscopy (TEM). Significance of the proposed research: The proposed programme aims to further expand research capabilities in the area of non-invasive studies of CNS tissue in animals in vivo. Quantitative, non-invasive imaging technology developed throughout this programme will help to broaden our understanding of animal CNS biology and physiology. In addition this programme will provide excellent opportunities for training graduate students and post-doctoral fellows in an interdisciplinary environment.