(A) study on fast NMR imaging by spiral scanning method

Abstract

In this thesis, a new fast NMR imaging method using Spiral Scanning Imaging (SSI) technique is proposed and experimented with KAIS 1.5 KGauss resistive magnet system. By SSI technique whole spatial frequency domain data is obtained by scanning along the Archimedes spiral curve with time varying oscillating gradients. No abrupt changes in gradient waveforms make it advantageous for the transient effect because of the gradient coils inductance. The proposed new method is compared to the other fast NMR imaging algorithms. No serious one-directional degradation by $T_2^\star$ decay is observed and found to be a characteristic for the proposed method. Transient responses of oscillating gradient waveforms for given gradient coils is analyzed and its compensation schemes are proposed. As a suggested method, an improved version of SSI, which is named "Butterfly pulse sequence" was tested in an attempt to eliminate $T_2^\star$ decay effect during data aquisition.