Prevention of Ground Pad During Radiofrequency Tumor Ablation

描述（由申请人提供）：射频（RF）消融是一种很有前途的微创热基方法，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，射频电流施加到电极上，导致离子搅拌和组织加热。肿瘤一旦达到50℃就被凝固性坏死破坏。射频消融的主要优点之一是它可以以微创方式应用，导致患者快速恢复和低发病率。最初的射频设备使用25 W功率，产生1.5 cm直径的凝固区，而目前的设备使用200 - 250 W功率，产生4-6 cm直径的凝固区。当前射频设备的一个主要限制是，由于凝血区大小不足，单次消融无法治疗中等大小的肿瘤（bb0 - 3cm）。因此，未来的设备可能会继续朝着更高的发电机功率和多个电极的趋势发展，以增加混凝区的大小并减少处理时间。使用高功率射频发生器和增加凝血区域的主要障碍是地面垫加热，在严重的情况下可能导致三度皮肤烧伤。目前，严重皮肤烧伤（二度或三度）的地面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%。由于射频电流在地垫下的不均匀分布，最靠近电极的边缘是最高皮肤温度和最可能发生烧伤的地方。在临床消融术中，两到四个地垫与消融术电极等距放置，通常在大腿周围。在远离电极的地方增加额外的接地垫只能提供最小的改进，因为射频电流优先流向最近的接地垫。到目前为止，减少地面垫相关加热的尝试仅限于优化垫的位置、垫的形状和垫的冷却。我们建议通过顺序激活地垫，并在垫下添加一层导电凝胶，来调制每个垫下的射频电流和相关加热。从而射频电流在多个焊盘之间均匀分布，减少了相关的发热，并且可以任意放置焊盘，而不受与射频电极处于相同距离的电流限制。这种方法可以提高发电机的功率，减少皮肤烧伤的可能性。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，治疗时间将缩短，成功率可能会提高。

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.