(A) study of 3-dimensuinal NMR imaging method andalgorithms and their applications

Abstract

3-Dimensional NMR imaging methods and algorithms and their applications are studied. Among others, multislice line-integral projection method, flow velocity imaging, and parameter extraction from image data are discussed. Line-integral projection reconstruction (LPR) in NMR imaging was found to be useful for certain cases, namely such as short $T_1$ imaging and data acquisition where compensation of phase fluctuations are needed due to the system instability. By use of encoding technique in conjunction with LPR method it is possible to excite a large volume which is found to be efficient because this leads to high SNR multislice regional imaging. Among many multislice LPR imaging methods, two basic forms using line-integral projection reconstruction are studied in this thesis, i.e., Fourier and Hadamard-like encoding methods. In addition, an optimization study of the imaging condition for a more accurate parameter extraction is studied. Next, a new NMR flow velocity imaging method for high speed flow is proposed and discussed. In the proposed technique, a selection gradient allows us to measure high velocity flow. To find the useful phase-velocity relation of flow under the selection gradient and echo RF pulse, the Bloch equation is numerically solved. Flow effect compensation other than slice selection direction is achieved by additional flow coding gradients similar to conventional flow phase coding. Computer simulations as well as experiments were carried out and the results are presented. Applications of the methods to the experimental NMR imaging show good agreement with predicted behavier.