Direct fourier transform 3-D image reconstruction with modified concentric square sampling

Abstract

This thesis consists of two parts; NMR algorithm in part 1 and RF coil/coupler design in part 2 respectively. In part 1, a 2 and 3-D image reconstruction algorithm, using direct Fourier transform technique along with a new projection scheme and Fourier domain interpolation, is proposed. The new proposed method does not require backprojection procedure unlike the conventional Fourier convolution backprojection method so that reconstruction can be performed with greater speed and simplicity. Further we have investigated possibility of applying the new method to NMR tomographic imaging in which some advantages were found. Some unique features of the new imaging method when applied to NMR tomography have been studied, especially advantages and disadvantages of the method compared with Fourier convolution backprojection method. In part 2, an RF coil and coupler unit for 1 KG (corresponding to Lamor frequency of 4.257 MHz) static magnetic field has been designed and analyzed. This unit transmits the high RF power to the object without any significant impact on receiver, and also receives the nuclear signal in the form of FID which is induced by RF coil. We have considered various factors in designing the RF coil/coupler scheme suitable for k KG NMR imaging experiment of human head section. A frame supporting the RF coil has also been designed and installed. Overall operations and performances are tested and experimented.