B1 MAPPING NEAR METALLIC IMPLANTS

这个子项目是利用资源的许多研究子项目之一。 由NIH/NCRR资助的中心拨款提供。对子项目的主要支持 子项目的首席调查员可能是由其他来源提供的， 包括美国国立卫生研究院的其他来源。为子项目列出的总成本可能 表示该子项目使用的中心基础设施的估计数量， 不是由NCRR赠款提供给次级项目或次级项目工作人员的直接资金。 在测试植入金属的MR兼容性时，功率或特定吸收率(SAR)的估计是重要的 物体。通过翻转角度图进行B1映射，是一种常用的实验确定SAR的工具。作为数量的 在矫形外科手术中使用的金属植入物增加了[1]，因此需要准确和安全的成像 技术。脉冲序列的最新进展，如SEMAC[2]，通过以下方式使金属植入物附近的MRI成为可能 校正存在的图像伪影并允许改善图像质量。尽管取得了这些进展，但更多的实验 需要执行，以确保新的序列符合SAR限制[3]，并且不会导致过热 纸巾。 在核磁共振成像中，射频激励场的测量是一个具有挑战性的问题。此外，B0的不均匀性使得B1映射接近 金属植入物尤其困难。目前可用的基于梯度回波和自旋的B1映射方法 回声技术[4，5]还没有被成功地用于金属植入物。这主要是由于信号丢失造成的 金属附近的敏感度和成像伪影增加。 要了解卢卡斯中心正在进行的其他项目，请访问http://rsl.stanford.edu/(卢卡斯年度报告和 ISMRM 2011年摘要)

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Power or specific absorption rate (SAR) estimations are important when testing the MR compatibility of implanted metallic objects. B1 mapping through flip angle maps, is a tool often used to determine SAR experimentally. As the number of metallic implants used during orthopedic surgeries increases [1], there is a need for an accurate and safe imaging technique. Recent developments in pulse sequences such as SEMAC [2], has enabled MRI near metallic implants by correcting image artifacts present and allows for improved image quality. Despite these advancements, more experiments need to be carried out to make sure that the new sequences comply with SAR limits [3] and do not cause overheating of tissues. In MRI, the measurement of RF excitation fields is challenging. Futhermore, B0 inhomogeneities make B1 mapping near metallic implants especially difficult. Currently available B1 mapping methods that are based on gradient echo and spin echo techniques [4,5] have not been successfully used around metallic implants. This is mostly due to signal loss from increased susceptibility and imaging artifacts near metal. To read about other projects ongoing at the Lucas Center, please visit http://rsl.stanford.edu/ (Lucas Annual Report and ISMRM 2011 Abstracts)