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

尽管与核磁共振相关的不良事件很少，但射频加热引起的安全问题有很大的影响 对临床使用的影响，特别是对越来越多的医用植入物患者。现行法规 基于估计的全身吸收率(SAR)对射频功率水平施加不必要的限制， 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问题 病人。具有局部电场和温度测量能力的微型传感器，可用于个别患者 在扫描过程中可以缓解这些限制，同时提高安全性。这些传感器也可以产生影响 关于介入MRI的应用，其中有源标记，本质上是局部测量RF的微型线圈 信号，提供最佳的设备可见性。然而，这些标记受到射频感应过导热的影响。 传输线，这一问题在高场磁共振系统中会加剧，目前没有 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音响- 光学(AO)射频场传感器，检测并通过光纤而不是传输线传输射频信号 这是一种新型的传输线，因此完全不会受到射频感应加热和电磁干扰。这个 相同的设备有可能测量温度以及用于SAR评估的局部E/H场 再加上一个设计得当的天线。在这个应用中，我们的目标是优化声光传感器的设计 使用0.55T、1.5T和3T系统的Larmor频率下光纤的独特机械共振 利用微细加工技术制作薄膜压电换能器器件。我们还提出了一部小说 将这些声光射频场传感器嵌入到套筒中的包装策略，可以符合任何商业用途 提供与MRI兼容的导管，大大增加了介入MRI的设备选择。这些 活动标记物和多参数E/H场传感器将根据最新的MRI安全性进行严格测试 标准，并在体内评估了几种具有挑战性的心血管介入性磁共振检查程序。 利用非导电传输线成功演示了AO传感器作为有源MRI标记的作用 将是更有效、更高效、更安全、新颖和无辐射介入的重大发展 程序。用于局部射频剂量测量的组合定量射频场和温度传感能力 通过扩大MRI安全范围来影响临床实践的潜力以及有助于 基本了解耦合效应，如B场耦合、驻波和梯度线圈效应 在当地的特别行政区。

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.