A Magnetic Resonance Imaging Study of the Brain and the Spinal Cord During Ischemia

Abstract

Nuclear magnetic resonance (NMR) is a physical method that has been used mainly as an analytical method by chemists to determine the structure of molecules in solution. There are two main applications of NMR in biomedical research and clinical practice: magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) (1). MRI has been restricted mainly to ¹ H owing to the superior sensitivity and abundance of this nucleus. The “mapping” of the protons takes advantage of the fact that relaxation times of the protons vary according to their environment. The spin-spin relaxation times (T₂) of protons in the white matter are 80–90 ms and of protons in the gray matter they are 90–100 ms. This provides discrimination between the protons of different tissues and yields high resolution images (2). Magnetic resonance imaging is very well established as a clinically useful diagnostic tool which helps establishing diagnosis and prognosis after brain and spinal cord injuries (3,4,5). The different MRI methods have been developed to improve the possibilities for studying the central nervous system pathology e.g. T₁ and T₂ weighted images (2), diffusion weighted images (6), echo-planar imaging (7) and combined imaging and spectroscopy (2).