Safe Ultrasonic Transmission Lines for MRI Catheters

描述(申请人提供)：由于减少了手术时间、患者不适、住院时间和与手术相关的风险，基于导管的微创介入治疗正成为比外科手术更受欢迎的方法。虽然X射线透视被广泛用于微创手术，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)可以提供优越的软组织对比度，同时消除这些手术中患者和操作员的电离辐射暴露。核磁共振还提供多层成像，并允许进行生理测量，如血流、温度、灌注和运动。MRI引导介入的一个重要问题是，大多数传统的介入设备(导管、导丝等)要么隐形，要么不适合在磁共振下使用。有源接收器使用导管轴上的小线圈或偶极天线来检测射频信号，以便在MRI下进行设备定位和/或定向，使用长传导传输线。这些方法是有问题的，因为在进行临床试验之前，需要解决设备的长导体组件上的射频感应加热问题。尽管已经通过失谐、射频扼流圈或变压器实现了在射频感应加热问题方面有希望的改善，但这些技术都不能提供具有临床可接受机械性能的有源设备设计。在这一应用中，我们的目标是开发一种临床级的有源导管装置，它不需要很长的导线传输线来在MRI下进行有源装置的可视化。有源导管设计包括一个远端环状线圈，该线圈与具有类似外形的超声换能器电连接。这种超声换能器在沿着有源导管轴延伸的介质光纤的远端处感应拉莫尔频率的超声波。这种光纤作为传输线而不是导体，消除了射频感应加热。超声换能器产生的应变将使用光学干涉测量法测量，方法是利用声光效应在光纤近端耦合激光。一种纤维 为此，将使用嵌入式布拉格反射光栅。有源设备将被设计、制造并整合到临床级导管原型中。原型将在核磁共振下进行测试：使用专门准备的体模进行体外测试，并在NHLBI设施的大型动物体内进行测试。

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.