LOCAL B1 SHIMMING FOR PROSTATE IMAGING//TRANSCEIVER ARRAYS AT 7 TESLA

这个子项目是许多利用 由NIH/NCRR资助的中心赠款提供的资源。子项目及 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 用收发器获得高质量的前列腺图像 在执行受试者相关局部传输后，在7 T下的阵列 B1（B1）匀场，以最大限度地减少破坏性 干扰B1匀场通过改变 各个RF通道的输入相位基于相对 B1相位图在体内快速获得的每个通道的 八元件带状线线圈。相对发射相位 需要在有限的区域内最大限度地提高B1的一致性 前列腺周围的组织与线圈指示的组织有很大不同 几何学，并且高度依赖于学科。一组发射 由B1匀场确定的相位提供了发射增益 效率4.2 2.7前列腺中， 由线圈几何形状确定的标准发射相位。这 效率的提高大大减少了所需的射频 前列腺中给定翻转角的功率，当考虑 在建模研究中， 局部特定吸收率。此外，B1垫片 前列腺内B1不均匀性降低， （二十四） 9%）至（5 4%）。这项研究表明， 快速局部B1相位匀场对永磁同步电机磁场影响 现场身体成像

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. High-quality prostate images were obtained with transceiver arrays at 7T after performing subject-dependent local transmit B1 (B1 ) shimming to minimize B1 losses resulting from destructive interferences. B1 shimming was performed by altering the input phase of individual RF channels based on relative B1 phase maps rapidly obtained in vivo for each channel of an eight-element stripline coil. The relative transmit phases needed to maximize B1 coherence within a limited region around the prostate greatly differed from those dictated by coil geometry and were highly subject-dependent. A set of transmit phases determined by B1 shimming provided a gain in transmit efficiency of 4.2 2.7 in the prostate when compared to the standard transmit phases determined by coil geometry. This increased efficiency resulted in large reductions in required RF power for a given flip angle in the prostate which, when accounted for in modeling studies, resulted in significant reductions of local specific absorption rates. Additionally, B1 shimming decreased B1 nonuniformity within the prostate from (24 9%) to (5 4%). This study demonstrates the tremendous impact of fast local B1 phase shimming on ultrahigh magnetic field body imaging.