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 90 degrees RF pulses with short repetition time, we have obtained a coronary angiogram around the heart including the coronary arteries and veins. The cine NMR imaging technique is also 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 postprocessing. The final 3-D angiogram is then formed by stacking the 2-D images and contrast is further enhanced by the maximum ray tracing algorithm.

A new echo-time-encoded chemical-shift imaging technique applicable to dual-peak spectroscopic imaging with large magnetic field inhomogeneity is proposed and studied. The basic concept and its applications to modest field homogeneity (approximately 3.0 ppm) as well as to relatively large field inhomogeneity (approximately 10.5 ppm) are discussed. Actual pulse sequences are given and some experimental results on human volunteers obtained with a 2.0-T KAIS NMR system are also presented.

A simple and new flow velocity measurement technique using conventional spin-echo sequence is proposed and its applications to a preclinical result are presented. This technique utilizes the phase velocity encoding effect due to 180 degrees rf and its corresponding selection gradient. This phase encoding and its phase velocity relations have been obtained by numerical solution of the Bloch equation. A flow velocity measurement obtained with a volunteer using this proposed technique indicates close agreement with other previously measured values.

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A new nuclear magnetic resonance (NMR) flow-velocity-imaging method applied to the study of the fluid dynamics is introduced. In the proposed technique, a selection gradient is used for the phase encoding, and since the selection gradient is relatively small compared with the conventional gradient for phase encoding it allows the measurement of high-velocity flow. To obtain the phase-velocity relationship, the Bloch equation is solved numerically and establishes the quantitative phase-velocity relationship of the flow under the slice selection gradient and echo radio frequency pulse. The flow effect compensation in the directions other than the slice selection direction is achieved by applying additional flow coding gradients similar to the conventional flow phase coding. The experimental NMR flow images obtained with the new technique are compared with the velocity measurements made with a laser Doppler velocimeter, and are found to be in close agreement.