Prevention of Ground Pad During Radiofrequency Tumor Ablation

描述（由申请人提供）：射频（RF）消融是一种有前景的微创热消融方法，用于消融肝癌、肾癌、骨癌和肺癌。在成像引导下，将电极插入肿瘤中，并将射频电流施加到电极上，从而导致离子搅动和组织加热。一旦肿瘤达到>50 ℃，就会被凝固性坏死破坏。射频消融的主要优点之一是它可以以微创方式应用，从而使患者恢复迅速，发病率低。最初的射频器械使用25 W功率并创建直径为1.5 cm的凝固区，而当前器械使用200 - 250 W功率并创建直径为4-6 cm的凝固区。当前RF装置的一个主要限制是由于凝固区的尺寸不足而不能用单次消融治疗甚至中等尺寸的肿瘤（> 3cm）。因此，未来的器械可能会继续向更高的发生器功率和多个电极发展，以增加凝固区的大小并减少治疗时间。采用更高功率的射频发生器和增加凝固区的主要障碍是接地垫加热，这在严重情况下可能导致三度皮肤烧伤。目前，严重皮肤烧伤（2度或3度）的接地垫皮肤烧伤发生率为0.1 - 3.2%，轻度皮肤烧伤发生率为5- 33%。由于接地垫下方的RF电流分布不均匀，最靠近电极的边缘是最有可能发生最高皮肤温度和灼伤的地方。在临床消融手术中，2 - 4个接地垫与消融电极等距放置，通常在大腿周围。在离电极更远的地方添加额外的接地垫将仅提供最小的改进，因为RF电流优先行进到最近的垫。到目前为止，减少接地垫相关发热的尝试仅限于优化垫放置、垫形状和垫的冷却。我们建议通过顺序激活接地垫并在垫下方添加一层导电凝胶来调制每个垫下方的RF电流和相关加热。因此，RF电流均匀地分布在多个焊盘之间，减少了相关的加热，并且焊盘可以任意放置，而没有与RF电极相距相同距离的电流限制。这种方法将实现更高的发生器功率，并降低皮肤烧伤的可能性。该项目与公共卫生的相关性：该项目的成功完成将使肝癌得到更有效的治疗。医生将能够治疗更大的肿瘤，治疗时间将减少，成功率可能会增加。

DESCRIPTION (provided by applicant): Radiofrequency (RF) ablation is a promising, minimally invasive heat-based method used to ablate cancer of the liver, kidney, bone, and lung. Under imaging guidance, an electrode is inserted into the tumor, and radiofrequency current is applied to the electrode resulting in ionic agitation and tissue heating. The tumor is destroyed by coagulative necrosis once it reaches >50 ¿C. One of the major advantages of RF ablation is that it can be applied in a minimally invasive fashion, resulting in rapid patient recovery and low morbidity. Initial RF devices used 25 W power and created 1.5 cm diameter coagulation zones, while current devices use 200 - 250 W power and create 4-6 cm diameter coagulation zones. One major limitation of current RF devices is the inability to treat even moderate size tumors (> 3 cm) with a single ablation due to insufficient size of the coagulation zone. Therefore future devices will likely continue the trend towards higher generator power and multiple electrodes to increase the size of coagulation zone and decrease treatment times. A major obstacle in employing higher power RF generators and enabling increased coagulation zones is ground pad heating, which can lead to 3rd degree skin burns in severe cases. The current incidence of ground pad skin burns ranges from 0.1 - 3.2 % for severe skin burns (2nd or 3rd degree), with mild skin burns ranging between 5-33 %. Due to inhomogeneous distribution of RF current below the ground pads, the edge closest to the electrode is where the highest skin temperatures and burns are most likely occur. In clinical ablation procedures, two-to-four ground pads are placed equidistant from the ablation electrode, usually around the thighs. Adding additional ground pads further away from the electrode will only provide minimal improvement, since RF current travels preferentially to the closest pads. Attempts in reducing ground pad related heating so far have been limited to optimizing pad placement, pad shape, and cooling of the pads. We propose to modulate the RF current and associated heating below each pad by sequentially activating ground pads, and adding a layer of electrically conductive gel below the pads. Thereby RF current is distributed evenly among multiple pads, related heating is reduced, and pads can be placed arbitrarily without the current limitation of being at the same distance from the RF electrode. This method will enable higher generator power, and reduce the likelihood of skin burns. Relevance of this project to public health: Successful completion of this project will enable more effective treatment of liver cancer. Physicians will be able to treat larger tumors, treatment times will be reduced, and success rates may increase.