Safe Ultrasonic Transmission Lines for MRI Catheters

描述（由申请人提供）：与外科手术相比，基于导管的微创介入治疗由于减少了手术时间、患者不适、住院时间和手术相关风险而成为首选方法。虽然X射线透视被广泛用作微创手术的成像引导，例如阻塞性冠状动脉疾病、外周动脉粥样硬化和动脉瘤以及结构性或先天性心脏病的治疗，但磁共振成像（MRI）可以提供上级软组织对比度，同时消除这些手术中患者和操作者的电离辐射暴露。MRI还提供多切片成像，并允许生理测量，如血流、温度、灌注和运动。MRI引导介入的一个重要问题是，大多数传统的介入器械（导管、导丝等）或者不可见或者不适合在MRI下使用。在导管轴上使用小线圈或偶极天线以在MRI下检测用于器械位置和/或方向的RF信号的有源仅接收器械使用长导电传输线。这些方法存在问题，因为在进行临床试验之前，需要解决器械长导体组件上的RF感应加热问题。尽管通过失谐、RF扼流圈或变压器在RF感应加热问题方面取得了有希望的改善，但这些技术都无法提供具有临床可接受机械性能的有源器械设计。在本申请中，我们的目标是开发一种临床级有源导管器械，该器械不需要长导体传输线即可在MRI下实现有源器械可视化。有源导管设计包含远端环形线圈，其电连接到具有可比轮廓的超声换能器。该超声换能器在沿有源导管轴沿着延伸的介电光纤的远端处以拉莫尔频率感应超声波。该光纤用作传输线而不是导体，消除了RF感应加热。超声换能器产生的应变将使用光学干涉测量法通过使用声光效应在光纤近端耦合激光来测量。纤维 嵌入式布拉格反射器光栅将用于此目的。将设计、制造有源器械并将其纳入临床级导管原型。原型将在MRI下进行测试：使用专门制备的体模进行体外测试，并在NHLBI机构的大型动物中进行体内测试。

DESCRIPTION (provided by applicant): Catheter based minimally invasive interventions are becoming a preferred method as compared to surgical procedures due to the reduction of operation time, patient discomfort, hospitalization time, and procedure related risks. While X-ray fluoroscopy is widely used as a imaging guidance for the minimally invasive procedures such as treatment of obstructive coronary artery disease, peripheral artery atherosclerosis and aneurysm, and structural or congenital heart disease, magnetic resonance imaging (MRI) can provide superior soft tissue contrast while eliminating the ionization radiation exposure on both patient and operator in these procedures. MRI also provides multi slice imaging and allows physiological measurements such as blood flow, temperature, perfusion and motion. A significant issue with MRI guided interventions is that most traditional interventional devices (catheters, guidewires etc.) either invisible or not suitable for use under MRI. Active receive-onl devices using small coils or dipole antennae on the catheter shaft to detect the RF signals for device location and/or orientation under MRI use long conductive transmission lines. These approaches are problematic as RF induced heating over long conductor components of the devices needs to be addressed before moving on clinical trials. Although promising improvements in terms of RF induced heating problem have been achieved by detuning, RF chokes or transformers, none of these techniques can offer active device design that can have clinically acceptable mechanical performance. In this application, we aim to develop a clinical-grade active catheter device that does not need long conductor transmission lines for active device visualization under MRI. The active catheter design incorporates a distal loop coil that is electrically connected to an ultrasonic transducer having a comparable profile. This ultrasonic transducer induces ultrasonic waves at the Larmor frequency at the distal end of a dielectric optical fiber that runs along the active catheter shaft. This optical fiber serves as the transmission line instead of a conductor, eliminating the RF induced heating. The strain generated by the ultrasound transducer will be measured using optical interferometry by coupling a laser at the proximal end of the optical fiber using the acousto-optical effect. A fiber embedded Bragg reflector grating will be used for this purpose. The active devices will be designed, fabricated and incorporated into clinical grade catheter prototypes. The prototypes will be tested under MRI: in-vitro using specially prepared phantoms and in-vivo in large animals at NHLBI facilities.