Study of direct fourier transform NMR tomography and its applications

Abstract

NMR imaging is derived from NMR spectroscopy with the addition of field gradients. The deliberately added magnetic field gradients together with the multiple or composite frequency r.f. pulse makes NMR tomography different from the conventional NMR spectroscopy. The paper deals with NMR tomography using the Direct Fourier transform methods. An indepth study of the direct Fourier reconstruction (DFR) and Hutchison-KWE (Kumar-Welti-Ernst) method is presented. Since the methods are direct Fourier transform methods, they do not require backprojection operation, and therefore reconstruction can be performed with greater speed and simplicity. In addition, image bluring in NMR tomography due to the chemical shift has been predicted and experimentally observed. We have analysed this chemical shift effects on image and made computer simulations of the effects both in the projection type of reconstruction and direct Fourier imaging. The effects have been systematically studied in various situation and possible correction schemes have been deduced.