Ultra-high-field Clinical Magnetic Resonance Imaging—Challenges and Excitement
physiologic interferences, including cardiac pulsation, respiration, peristalsis, and swallowing, cause unwanted fluctuations of signal intensity and phase that are much more severe than in lower-field-strength conventional MRI. B0 fluctuations in body imaging can be induced by susceptibility changes during respiration attributed to movements of the chest and diaphragm and by variations in the oxygen concentration. The overall imaging field of view and the size of the coils are much larger in comparison with neuroimaging. The tissues within the field of view or the target imaging areas are also much more heterogeneous than those in CNS and MSK imaging. With the development of improved RF coils to overcome problems of B1 inhomogeneity and the advent of multichannel transmit systems to reduce SAR, UHF body imaging is becoming possible. Preliminary results show the feasibility of UHF
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Conclusion
UHF MRI is likely to continue to play an exciting role in the near future as more UHF units are installed and more clinical results are available for public investigation. As technical advances and cost reductions continue to occur, the cost-effectiveness of UHF MRI will likely continue to improve in the near future. Ultimately, the future of UHF MR will be determined by technical advances, success in identifying the optimal field strength, and, perhaps most importantly, the cost-effectiveness—particularly under the scrutiny of the current cost-containment-conscious healthcare environment. n
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