Celik Haydar, Ulutürk Asli, Tali Turgut, Atalar Ergin
Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey.
Magn Reson Med. 2007 Dec;58(6):1224-31. doi: 10.1002/mrm.21419.
To conduct interventional procedures in MRI, reliable visualization of interventional devices such as catheters is necessary. For this purpose, the use of inductively-coupled radio frequency (ICRF) coils has been proposed. Without a wired connection, the signal around the ICRF coil is amplified, enabling catheters to be visualized. The wireless connection allows easy handling of catheters, in some pulse sequences, however, it might be difficult to differentiate the catheters from anatomical background information. In this work, a novel ICRF coil visualization method, which allows separation of the catheter and the anatomical information by using the reverse and forward polarization modes of a coil, is proposed. This method allows images of the anatomy and the catheter to be combined into a color-coded image. First, an ICRF coil with decoupling diodes was constructed; we call this a receive-coupled RF (RCRF) coil. The RF safety profile of the RCRF coil is shown to be better than the ICRF coil. Second, to demonstrate the feasibility of this method, a receive-only birdcage coil without a hybrid coupler was constructed and then connected to a scanner as a two-channel phased-array coil. MR signals acquired from two channels were added after phase adjustments to create the reverse and forward polarization mode images. The reverse polarization mode image contained signal only from the RCRF coil, but the forward polarization mode displayed both anatomical information and the RCRF coil. The performance of this novel tracking method was tested in phantom and animal experiments. Color-coded images demonstrate the feasibility of the method to track catheters using RCRF coils.
要在磁共振成像（MRI）中进行介入操作，导管等介入设备的可靠可视化是必要的。为此，有人提出使用电感耦合射频（ICRF）线圈。在没有有线连接的情况下，ICRF线圈周围的信号会被放大，从而使导管能够被可视化。无线连接便于导管的操作，然而，在某些脉冲序列中，可能难以将导管与解剖背景信息区分开来。在这项工作中，提出了一种新颖的ICRF线圈可视化方法，该方法通过使用线圈的反向和正向极化模式来分离导管和解剖信息。这种方法允许将解剖结构和导管的图像组合成彩色编码图像。首先，构建了一个带有去耦二极管的ICRF线圈；我们将其称为接收耦合射频（RCRF）线圈。结果表明，RCRF线圈的射频安全特性优于ICRF线圈。其次，为了证明该方法的可行性，构建了一个没有混合耦合器的纯接收鸟笼线圈，然后将其作为双通道相控阵线圈连接到扫描仪上。在进行相位调整后，将从两个通道采集的磁共振信号相加，以创建反向和正向极化模式图像。反向极化模式图像仅包含来自RCRF线圈的信号，而正向极化模式则同时显示了解剖信息和RCRF线圈。在体模和动物实验中测试了这种新颖跟踪方法的性能。彩色编码图像证明了使用RCRF线圈跟踪导管的方法的可行性。
