Acousto-optical RF field sensors for safer diagnostic and interventional MRI

尽管与MRI相关的不良事件很少见，但由于射频致热引起的安全性问题具有显著的 对临床使用的影响，特别是对越来越多的植入医疗植入物的患者。现行规定 基于估计的全身吸收率（SAR）对RF功率水平施加了不必要的限制， 有时会降低诊断效率，而即使是这些低水平也会产生特定的安全性问题。 患者具有局部电场和温度测量能力的微型传感器 在扫描过程中可以减轻这些限制，同时提高安全性。这些传感器也会产生影响 在介入性MRI应用中，有源标记物，基本上是局部测量RF的微型线圈， 信号，提供最佳的设备可视性。然而，这些标记物在传导性上遭受RF感应加热， 传输线，这是一个在更高场MR系统中加剧的问题，目前还没有解决方案。 满足所有机械和电气约束的解决方案。我们最近开发了一种微型声学- 光学（AO）RF场传感器，其检测RF信号并通过光纤而不是导电的来传输RF信号 因此，它完全不受射频感应加热和电磁干扰的影响。的 同一器械有可能测量温度以及局部E/H场，用于SAR评价， 再加上设计合理的天线在这个应用中，我们的目标是优化AO传感器的设计 在0.55T、1.5T和3 T系统的拉莫尔频率下使用光纤的独特机械共振， 利用微加工技术制造具有薄膜压电换能器的器件。我们还提出了一个新的 将这些AO RF场传感器嵌入套管中的包装策略， 可用的MRI兼容导管，以显著增加介入性MRI的器械选择。这些 有源标记和多参数E/H场传感器将根据最新的MRI安全标准进行严格测试 标准，并在体内评价了几种具有挑战性的心血管介入MRI程序。 成功证明AO传感器作为有源MRI标记（带非导电传输线） 将是更有效、更高效、更安全、新型、无辐射介入治疗的重大发展， 程序.用于局部RF剂量测定的组合定量RF场和温度感测能力具有 通过扩大MRI安全范围以及促进 基本了解耦合效应，如B场耦合、驻波和梯度线圈效应 在当地搜救

Although adverse events related to MRI are rare, safety concerns due to RF induced heating have a significant impact in clinical use especially for a growing number of patients with medical implants. Current regulations based on estimated whole body absorption rate (SAR) impose unnecessary restrictions on RF power levels, sometimes reducing the diagnostic efficacy, while even these low levels can create safety issues for specific patients. Miniature sensors with local E-field and temperature measurement capability on individual patients during the scans can alleviate these limitations while improving safety. These sensors can also have an impact on interventional MRI applications where active markers, essentially miniature coils that locally measure the RF signal, provide the best device visibility. These markers, however suffer from RF induced heating over conductive transmission lines, an issue that gets exacerbated in higher field MR systems and does not currently have a solution that satisfies all mechanical and electrical constraints. We recently developed a miniature acousto- optical (AO) RF field sensor which detects and transmits the RF signal over an optical fiber instead of conductive transmission lines, and therefore is totally free of RF induced heating and electromagnetic interference. The same device has the potential to measure temperature as well as the local E/H field for SAR evaluation when coupled with a properly designed antenna. In this application, we aim to optimize the design of the AO sensor using unique mechanical resonances of optical fibers at Larmor frequencies of 0.55T, 1.5T and 3T systems and use microfabrication techniques to make device with thin film piezoelectric transducers. We also propose a novel packaging strategy to embed these AO RF field sensors in sleeves that can conform to any commercially available MRI compatible catheter, to significantly increase the device options for interventional MRI. These active markers and multi-parameter E/H field sensors will be rigorously tested according to the latest MRI safety standards and evaluated in vivo for several challenging cardiovascular interventional MRI procedures. Successful demonstration of the AO sensor as an active MRI marker with a non-conducting transmission line will be a significant development for more effective, more efficient, safer, novel, and radiation-free interventional procedures. The combined quantitative RF field and temperature sensing capability for local RF dosimetry has the potential to impact clinical practice by broadening the MRI safety envelope as well as contributing to the fundamental understanding of coupling effects such as B-field coupling, standing waves and gradient coil effects on local SAR.