Advanced MRI Technology in Safety & Intervention

描述（由申请人提供）：这项MRI“技术发展”资助（R01 RR15396）由NCRR作为生物工程研究资助，现在角色转移到NIBIB。最初的拨款推动了当时的多通道高速MRI新技术，包括临床首台32通道平行MRI；局部梯度强度和速度增加~10倍；优化信噪比（SNR）检测器；条带探测器的发明；在1.5特斯拉（1.5 t）的速度和性能上实现了数量级的提升。同时，临床3T MRI扫描仪已经到来，这一更集中的更新要求扩展了测温和探测器优化，以解决射频加热和剂量学的核心安全问题，以及3T内部探测器的安全性和潜在性能提升。这是为了应用于动脉粥样硬化的高分辨率成像而开发的。特别是，我们提供了新的初步体内和体外实验和理论数据，表明信号噪声比（SNR）提高了近四倍，3T时视场（FOV）面积增加了约10倍，血管壁分辨率提高了80-1505m。虽然3T提供更高的信噪比，但在MRI期间沉积的射频功率，比吸收率（SAR, W/kg）从1.5T到3T增加了四倍，所有其他方面都是相同的，这引起了真正的安全问题，从根本上限制了3T扫描仪的操作。然而，在评估新的MRI技术、调查MRI引起的射频烧伤、建立可靠的SAR水平以评估设备安全性或医学物理学家进行常规MRI质量评估时，目前还没有独立的方法来测量MRI期间的SAR，以确保符合FDA和/或IRB指南。主要的安全问题在Aim 1中得到解决，Aim 1开发了首个用于临床头部和身体MRI的SAR剂量计，并将其应用于烧伤报告后的扫描仪SAR评估和设备测试。目标2开发新的高信噪比内部检测器，解决3T时增加的加热和解耦问题，并将该技术应用于动脉粥样硬化动物模型。Aim 3将其扩展到一种新的MRI方法，该方法固有地锁定在内部检测器上，创造了真正的MRI内窥镜。内窥镜提供了直接从探头角度的显微成像，因为它是先进的，避免了用扫描仪询问探头位置的低效率。并在动脉粥样硬化模型上进行了实验。目标4回到剂量学，将我们的测温工作扩展到更高的潜力，在3T下对内部金属探测器进行射频加热，使用探测器本身作为独立的射频辐射计。这些生物工程方面的进步将广泛地造福于多个使用MRI的NIH研究所，并对这一关键模式的安全性做出重要贡献。公共卫生相关性：该资助为独立评估MRI射频功率沉积以监测其安全操作和评估植入设备的安全性提供了新技术。它将提供新的内部MRI探针，有望为局部高分辨率成像和MRI内窥镜提供更高的灵敏度和分辨率，在血管疾病和易损斑块的评估和治疗方面具有潜在的应用前景。

DESCRIPTION (provided by applicant): This MRI "technology development" grant (R01 RR15396) was funded by the NCRR as a Bioengineering Research grant, a role now shifted to NIBIB. The initial grant advanced the then new technologies of multi- channel high-speed MRI, including the first clinical 32-channel parallel MRI; local gradients with ~10-fold increases in strength and speed; optimized signal-to-noise ratio (SNR) detectors; the invention of strip detectors; and thermometry, achieving order-of-magnitude gains in speed and performance at 1.5 Tesla (1.5T). Meanwhile, clinical 3T MRI scanners have arrived, and this more-focused renewal request, extends thermometry and detector optimization to address core safety issues of RF heating and dosimetry, and the safety and potential performance gains of internal detectors at 3T. These are developed for applications to high-resolution imaging in atherosclerosis. In particular, we provide new preliminary in vivo and in vitro experimental and theoretical data suggesting a nearly quadrupling of signal-to-noise ratio (SNR), a ~10-fold gain in field-of-view (FOV) area at 3T, and 80-1505m resolution of vessel walls. While 3T delivers higher SNR, the RF power deposited during MRI, the specific absorption rate (SAR, W/kg), quadruples from 1.5T to 3T, all else being the same, raising genuine safety concerns that fundamentally limit 3T scanner operation. Yet, there are currently no independent means of measuring SAR during MRI for ensuring compliance with FDA and/or IRB guidelines when evaluating new MRI techniques, investigating RF burns caused by MRI, establishing reliable SAR levels for assessing device safety, or for routine MRI quality assessment by Medical Physicists. The central safety issue is addressed in Aim 1 which develops the first SAR dosimeter for clinical head and body MRI and applies it to assessing scanner SAR following burn reports, and to device testing. Aim 2 develops new high-SNR internal detectors, solving the increased heating and decoupling problems at 3T, and applying the technology to an animal model of atherosclerosis. Aim 3 extends this to a new MRI method that is inherently locked to the internal detector, creating a true MRI endoscope. The endoscope provides micro- imaging directly from the view-point of the probe as it is advanced, avoiding the inefficiencies of interrogating probe location with the scanner. It is also tested on the atherosclerosis model. Aim 4 returns to dosimetry, extending our thermometry work to the much higher potential for RF heating of internal metallic detectors at 3T, using the detector itself as an independent RF radiometer. These bio-engineering advances will broadly benefit the multiple NIH institutes that utilize MRI, and contribute importantly to the safety of this key modality. PUBLIC HEALTH RELEVANCE: This grant provides novel technology for independently assessing RF power deposition in MRI for monitoring its safe operation, and for evaluating the safety of implanted devices. It will provide new internal MRI probes that promise large sensitivity and resolution gains for local high-resolution imaging and MRI endoscopy, with potential applications to the assessment and treatment of vascular disease and vulnerable plaque.