(A) study on dynamic imaging and motion artefact reduction techniques in nuclear magnetic resonance tomography

Abstract

The development of NMR (uncelear 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 thchnique such as SSFP(Steady state free precession) and FLASH (fast low angle shot), and partly sucessul in obatining near real time flow dynamics of heart. For the dynamic study, i.e., high resoultion imaging of moving organs, the reductions of reriodic motion artefact, i.e., the cardiac and the respiratory motion artefacts, and the correcton 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 respiratiory syscles are essential. Obtaining of these physiological parameter with external ECG(electrocardiogram) gating device are, however, usually disturbed by several factros in NMR imaging such as the stactic magnetic field, gradient field, and RF excitation in system. In this thesis, the new techinques 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 respiratiory motion artefact reudction of the abdomical 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 r...