The development of NMR (unclear magnetic resonance) imaging promises many important medical applications such as the imaging of moving organs like heart. Recently, the dynamic imaging of heart has been studied and applied to the patient using many new techniques, i.e., the gradient echo technique such as SSFP(Steady state free precession) and FLASH (fast low angle shot), and partly successful in obtaining near real time flow dynamics of heart. For the dynamic study, i.e., high resolution imaging of moving organs, the reductions of periodic motion artefact, i.e., the cardiac and the respiratory motion artefacts, and the correction of flow artefacts are another important areas for the further study.
For the most of the dynamic imaging applications such as heart, abdominal imaging, and the flow artefact reduction in the head, the information on the cardiac and respiratory cycles are essential. Obtaining of these physiological parameter with external ECG(electrocardiogram) gating device are, however, usually disturbed by several factors in NMR imaging such as the static magnetic field, gradient field, and RF excitation in system.
In this thesis, the new techniques which effectively extract both cardiac and respiratory cycles directly from projection data has been developed and theoretically frame work of the method has been studied. These extracted basic physiological parameters have been applied successfully in the dynamic imaging of heart, the respiratory motion artefact reduction of the abdominal imaging, and the flow artefact reduction in the head. In section II, the basic concepts of the periodic cycle extraction from the projection data are described. In the section III, the dynamic imaging of heart using the extracted cardiac cycle is described. In section IV, the motion artefacts affected by respiratory and flow motion are analyzed and the existing reduction methods of motion artefacts are explained, respectively. In section V, motion and flow artefacts reduction using the extracted respiratory and cardiac cycles are described. In section VI, the experimental results are obtained to demonstrate the usefulness of the proposed techniques.
