Recent Problems of Electromagnetic Technology in MRI

Issei MORI  Yoshinori HAMAMURA  Hiromi KAWAMOTO  

IEICE TRANSACTIONS on Communications   Vol.E78-B   No.6   pp.809-817
Publication Date: 1995/06/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Medical Applications of Electromagnetic Techniques)
MRI,  gradient coil,  RF,  SAR,  NMR,  

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Though the electromagnetic technology has been contributing to the evolution of MRI, there are remaining problems to be worked out. With some introduction, this paper explains such problems focusing on the gradient coil design, RF coil design and RF safety consideration. For accurate, high-speed control of the gradient field, a new technology, shielded gradient coil has started playing an important role. The efficient design of such a coil requires a robust and efficient optimization tool that still has room for improvement. We propose to use the stored energy as the most important optimization parameter that may make the optimization process more efficient. Phased array RF coil, that widens the field of view while maintaining high SNR of a small RF coil, is a recent technology. For this, the system needs to have high capacity to acquire and process the data. To mitigate this problem, we are working on the combination of rather conventional QD technology with phased array. RF shielding between gradient coil and RF coil is becoming a serious problem with the evolution of high speed imaging techniques, and a complete solution is not yet demonstrated. We also discuss the difficulty of rigorous control of RF heating in patients. Practical method to predict local SAR needs to be developed.