B1 MAPPING NEAR METALLIC IMPLANTS

这个子项目是利用这些资源的众多研究子项目之一

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)