Real-time device tracking under MRI using an acousto-optic active marker.

This work aims to demonstrate the use of an “active” acousto-optic marker with enhanced visibility and reduced RF induced heating for interventional MRI. The acousto-optic marker was fabricated using bulk piezoelectric crystal and π-phase shifted fiber Bragg grating (FBGs) and coupled to a distal receiver coil on an 8F catheter. The received MR signal is transmitted over an optical fiber to mitigate RF induced heating. A photodetector converts the optical signal into electrical signal, which is used as the input signal to the MRI receiver plug. Acousto-optic markers were characterized in phantom studies. RF induced heating risk was evaluated according to ASTM 2182 standard. In vivo real-time tracking capability was tested in an animal model under a 0.55T scanner. SNR levels suitable for real-time tracking were obtained by utilizing high sensitivity FBG and piezoelectric transducer with resonance matched to Larmor frequency. Single and multiple marker coils integrated to 8F catheters were readout for position and orientation tracking by a single acousto-optic sensor. RF induced heating was significantly reduced compared to a coax cable connected reference marker. Real time distal tip tracking of an active device was demonstrated in an animal model with a standard real-time cardiac MR sequence. Acousto-optic markers provide sufficient SNR with a simple structure for real time device tracking. RF induced heating is significantly reduced compared to conventional active markers. Also, multiple RF receiver coils connected on an acousto-optic modulator can be used on a single catheter for determining catheter orientation and shape.

这项工作旨在展示一种用于介入式磁共振成像（MRI）的“有源”声光标记物的使用，该标记物具有更高的可视性以及更低的射频（RF）致热效应。 声光标记物是利用块状压电晶体和π相移光纤布拉格光栅（FBG）制成的，并与8F导管上的远端接收线圈耦合。接收到的磁共振信号通过光纤传输以减少射频致热。光电探测器将光信号转换为电信号，该电信号用作磁共振成像接收器插头的输入信号。在体模研究中对声光标记物进行了特性分析。根据ASTM 2182标准评估了射频致热风险。在0.55T扫描仪下的动物模型中测试了体内实时跟踪能力。 通过使用高灵敏度的光纤布拉格光栅以及共振频率与拉莫尔频率匹配的压电换能器，获得了适合实时跟踪的信噪比（SNR）水平。集成在8F导管上的单个和多个标记线圈可由单个声光传感器读出以进行位置和方向跟踪。与连接同轴电缆的参考标记物相比，射频致热显著降低。在动物模型中，利用标准的实时心脏磁共振序列展示了有源设备的远端实时跟踪。 声光标记物结构简单，可为设备实时跟踪提供足够的信噪比。与传统的有源标记物相比，射频致热显著降低。此外，连接在声光调制器上的多个射频接收线圈可用于单个导管上，以确定导管的方向和形状。