Static and dynamic imaging using magnetic field gradients = Jingtai yu dongtai heci chengxiang : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Physics at Massey University

Abstract

The theory and techniques of NMR imaging are described together with a detailed description of the Filtered Back Projection (FBP) technique used in an existing NMR imaging system. The existing 'static' NMR imaging system has been modified to be capable of performing 'dynamic' NMR imaging experiments, as well as better 'static' NMR imaging experiments. The potential of NMR microscopy in the imaging of both the static spin distribution P(rₒ) and the dynamic spin correlation function P(rₒ|r,t)has been investigated. Both homogeneous and inhomogeneous systems have been studied. Detailed theoretical analysis and experimental considerations of dynamic imaging experiments have been given. A transverse resolution of 15 µm for a 1 mm slice thickness is obtained from a static imaging experiment of a phantom using the modified system. The rabbit trachea imaging experiment has revealed the asymmetrical collapse of tracheas under negative pressures, a collapse which had previously been considered as symmetrical process. The Poiseuille flow experiment has involved the first simultaneous measurement of flow and diffusion at the microscopic level. Maps of two dimensional distribution functions of flow and diffusion are given by this experiment, highlighting this totally non-invasive dynamic imaging technique. As an example of dynamic imaging, the wheat grain experiment has displayed the flow and diffusion maps within a single wheat grain in vivo.