MR-Guided RF Ablation ofthe Liver

射频消融（RFA）是一种有效的图像引导微创治疗方法， 替代手术治疗癌症肿瘤。RFA似乎非常适合不可切除的肝脏肿瘤。 消融过程高度依赖于这些组织的电导率，然而， 预测电流路径或电流在肿瘤上的集中程度的方法。例如，骨和 脂肪囊可以保护肿瘤免受消融电流的影响。因此，可重复的消融体积是 很难生产。 我们的目标是通过使用MRI系统来增强肿瘤消融的计划，控制和效果， 在消融期间标测电极局部的RF消融电流并标测热变化。RF电流 地图将显示电力正在沉积的位置，MR温度测量将显示热量在 消融术我们的方法利用了一种新的MRI技术，估计组织中的RF电流密度。的 消融电极可以以MRI扫描器的谐振频率注入RF电流，并且可以 也可以作为MRI接收器。核磁共振扫描仪可以直接成像相关的强磁场 与消融电流，然后导出流向组织的局部电极电流。在我们的初步工作中， 我们已经可视化了MR兼容消融电极中的电流。这些测试 证明脂肪组织有效地绝缘和阻断消融电流。而且目前 通路本身照亮高传导性组织并产生医学上显著的对比度。 为了充分利用这一能力，我们将合并射频电流标测与磁共振测温和消融 器械，以形成用于射频消融的综合介入MRI系统。增强的射频硬件，脉冲 将开发序列和重建。完成后，我们将进行离体组织样本 和体内动物研究，以证明该系统的临床潜力。

Radiofrequency ablation (RFA) is emerging as an effective image-guided minimally invasive therapeutic alternative to surgical treatment of cancer tumors. RFA appears well suited to nonresectable tumors in liver. The ablation process is highly dependent on the electrical conductivity of these tissues yet there is no easy way to predict the current pathways or how focused the current will be on the tumor. For example, bone and fatty pockets can shield tumor from ablation currents. Consequently, repeatable ablation volumes are difficult to produce. Our goal is to enhance the planning, control and efficacy of tumor ablation by using an MRI system that can map RF ablation currents local to the electrodes during ablation and map thermal changes. RF current maps will show where power is being deposited, and MR thermometry will show where heat flowed during the ablation. Our approach exploits a new MRI technique that estimates RF current density in tissue. The ablation electrode can be injected with RF currents at the resonant frequency of the MRI scanner, and can also act as an MRI receiver. The MRI scanner can directly image the intense magnetic fields associated with the ablation current, and then derive the local electrode current flow to tissue. In our preliminary work, we have already visualized the current flow in an MR compatible ablation electrode. These tests demonstrated that fatty tissue effectively insulates and blocks the ablation current. Moreover, the current pathway itself lights up high conductivity tissue and creates a medically significant contrast. To fully exploit this capability, we will merge RF current mapping with MR thermometry and ablation devices to form a comprehensive interventional MRI system for RF ablation. Enhanced RF hardware, pulse sequences and reconstructions will be developed. Upon completion, we will perform ex-vivo tissue sample and in-vivo animal studies to demonstrate the clinical potential of this system.