B1 MAPPING NEAR METALLIC IMPLANTS

这个子项目是许多利用资源的研究子项目之一 由NIH/NCRR资助的中心拨款提供。子项目的主要支持 而子项目的主要调查员可能是由其他来源提供的， 包括其它NIH来源。 列出的子项目总成本可能 代表子项目使用的中心基础设施的估计数量， 而不是由NCRR赠款提供给子项目或子项目工作人员的直接资金。 当测试植入金属的MR兼容性时，功率或比吸收率（SAR）估计很重要 对象B1映射通过翻转角映射，是一种经常用于实验确定SAR的工具。 的数量 骨科手术中使用的金属植入物增加[1]，需要准确和安全的成像 法脉冲序列（如SEMAC [2]）的最新发展已使MRI接近金属植入物， 校正存在的图像伪影并允许改进的图像质量。尽管有这些进步，更多的实验 确保新序列符合SAR限值[3]，并且不会导致 组织中 在MRI中，RF激励场的测量具有挑战性。Fu，B 0不均匀性使B1映射接近 金属植入物尤其困难。基于梯度回波和自旋的当前可用B1标测方法 回波技术[4，5]尚未成功地用于金属植入物周围。这主要是由于信号丢失， 金属附近增加的敏感性和成像伪影。 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)