The basic principles of NMR flow imaging is generally discussed to help understanding the concept of the NMR flow imaging and the angiography technique, especially of the coronary angiography. Two categories of flow imaging method, i.e., phase sensitive method (velocity sensitive method) and in-flow sensitive method (time-of-flight method) are given for flow imaging and angiography. Early study of the phase sensitive techniques such as flow velocity map are presented together with the improved high-speed NMR flow-velocity measurement technique using a differential phase-encoding.
In this thesis, coronary vessel angiography which uses 3-D NMR angiography method with 2-D planar image scanning is suggested and its potential is shown by its experimental results for healthy volunteer. On the basis of the principles of the time-of-flight method and the 3-D angiogram obtained by the 2-D planar image scanning technique using glow rehased gradient echo sequence with 90˚ RF pulse and short repetition time a coronary angiogram has been attempted, In this technique in order to obtain the maximum contrast between heart wall and blood flow a 90˚ RF flip angle SSFP technique has been used in conjunction with thin slice selection. In addition, the cine NMR imaging technique is incorporated in synchronizing ECG R waves to reduce the motion artifact and at the same time to induce the saturation effect on the static samples. Images of the large bulk blood flow corresponding to the heart chamber and descending aorta are further removed by the postprocessing using boundary detection and segmentation. The final 3-D angiogram is then formed by stacking the 2-D images with and contrast is further enhanced by maximum ray tracing algorithm.
Scan time reduction of 3-D magnetic resonance angiography using a 2-D planar image scanning technique based on the time-of flight method and the time-multiplexed multislice acquisition technique is also proposed. The procedure involves the sequentially contiguous and simultaneous data acquisition of the two thin (1.2mm) 2-D planar slices by dividing imaging region into two part in the slice-selection direction. The 90˚RF pulse with short repetition time($
