TRD4 - Ultrahigh Field Engineering and Safety

点击翻译按钮获取中文摘要

PROJECT SUMMARY/ ABSTRACT The overall objective of TRD4 is to develop innovative engineering solutions required to support the other TRDs and various collaborative and service projects in this P41 Center. One of the most important issues that needs to be addressed, particularly while developing new ultra-high field MR technologies, is to ensure the overall MR related safety of the technology. We demonstrated the feasibility of accurately predicting temperature increase in anesthetized animals due to power deposition from antenna arrays at 10.5 T and will expand on this work and explore true safety limits of transmit arrays by investigating in-vivo absolute temperature change. We also propose a novel approach to monitor surface temperatures with IR cameras integrated into coil housings. Another significant technological barrier for the larger MR community is how to address the safety issues and imaging artifacts associated with metallic implants and deep brain stimulator leads. The use of MRI for measuring tissue structure and function in the presence of implanted leads is also critically important for research aimed at understanding the mechanisms and evaluating the impact of neuromodulation. Yet, most individuals with such metallic implants cannot undergo MR imaging because of severe, RF-induced image artifacts and tissue heating. Therefore, novel MRI strategies that minimize a priori the occurrence of artifacts and tissue heating are desperately needed. We propose to develop parallel RF transmission strategies expanding on the previous methods that were developed to predict and/or reduce heating around implants. The increased SNR available at UHF (7 T and 10.5 T), in combination with newly developed optimized RF coil designs, offers the potential of achieving unprecedented high-resolution images of the brain. However, as image resolution increases, the problem of head motion during acquisition causing artifacts and blurring becomes more substantial. To address this problem, improved motion detection and correction approaches are necessary. We propose to develop novel sensor hardware and to translate existing external software developments for improved motion detection and correction. The data provided by these sensors can also be used for other purposes such as safety monitoring. Finally, we plan to expand on our extensive UHF technology expertise and propose optimized transmit arrays and receive array combinations for head and body that combine proton and multinuclear imaging applications. Using ultrahigh dielectric constant materials (uHDC) in conjunction with multinuclear coils has been shown to potentially decrease RF power requirements while simultaneously increasing SNR and reducing SAR. The optimal permittivity is dependent on the resonant frequency of interest, which depends on the field strength and nucleus under investigation. The increase in the 10.5T operating frequencies for X-nuclei is expected to allow use of lower loss dielectrics with the potential of additional gains in SNR beyond the supralinear SNR increase due to the field strength.