Wildermuth S, Dumoulin C L, Pfammatter T, Maier S E, Hofmann E, Debatin J F
Institute of Diagnostic Radiology, University Hospital Zürich, Switzerland.
Cardiovasc Intervent Radiol. 1998 Sep-Oct;21(5):404-10. doi: 10.1007/s002709900288.
Magnetic resonance (MR)-guided percutaneous vascular interventions have evolved to a practical possibility with the advent of open-configuration MR systems and real-time tracking techniques. The purpose of this study was to assess an MR-tracking percutaneous transluminal angioplasty (PTA) catheter with regard to its safety profile and functionality.
Real-time, biplanar tracking of the PTA catheter was made possible by incorporating a small radiofrequency (RF) coil in the catheter tip and connecting it to a coaxial cable embedded in the catheter wall. To evaluate potentially hazardous thermal effects due to the incorporation of the coil, temperature measurements were performed within and around the coil under various scanning and tracking conditions at 1.5 Tesla (T). Catheter force transmission and balloon-burst pressure of the MR-tracking PTA catheter were compared with those of a standard PTA catheter. The dilatative capability of the angioplasty balloon was assessed in vitro as well as in vivo, in an isolated femoral artery segment in a swine.
The degree of heating at the RF coil was directly proportional to the power of the RF pulses. Heating was negligible with MR tracking, conventional spin-echo and low-flip gradient-echo sequences. Sequences with higher duty cycles, such as fast spin echo, produced harmful heating effects. Force transmission of the MR-tracking PTA catheter was slightly inferior to that of the standard PTA catheter, while balloon-burst pressures were similar to those of conventional catheters. The MR-tracking PTA catheter functioned well both in vitro and in vivo.
The in vivo use of an MR-tracking PTA catheter is safe under most scanning conditions.
随着开放式磁共振（MR）系统和实时跟踪技术的出现，MR引导下的经皮血管介入治疗已发展成为一种切实可行的方法。本研究的目的是评估一种MR跟踪经皮腔内血管成形术（PTA）导管的安全性和功能。
通过在导管尖端安装一个小型射频（RF）线圈并将其连接到嵌入导管壁的同轴电缆，实现了PTA导管的实时双平面跟踪。为了评估由于线圈的加入可能产生的有害热效应，在1.5特斯拉（T）的各种扫描和跟踪条件下，对线圈内部和周围进行了温度测量。将MR跟踪PTA导管的导管力传递和球囊破裂压力与标准PTA导管进行了比较。在体外以及在猪的离体股动脉段体内评估了血管成形术球囊的扩张能力。
RF线圈处的加热程度与RF脉冲的功率成正比。在MR跟踪、传统自旋回波和低翻转梯度回波序列下，加热可忽略不计。具有较高占空比的序列，如快速自旋回波，会产生有害的热效应。MR跟踪PTA导管的力传递略逊于标准PTA导管，而球囊破裂压力与传统导管相似。MR跟踪PTA导管在体外和体内均功能良好。
在大多数扫描条件下，MR跟踪PTA导管的体内使用是安全的。
