Rappaport C
Department of Electrical and Computer Engineering, Northeastern University, Boston, MA 02115, USA.
Int J Hyperthermia. 2004 Nov;20(7):769-80. doi: 10.1080/02656730412331286885.
The common condition of atrial fibrillation is often treated by cutting diseased cardiac tissue to disrupt abnormal electrical conduction pathways. Heating abnormal tissue with electromagnetic power provides a minimally invasive surgical alternative to treat these cardiac arrhythmias. Radio frequency ablation has become the method of choice of many physicians. Recently, microwave power has also been shown to have great therapeutic benefit in medical treatment requiring precise heating of biological tissue. Since microwave power tends to be deposited throughout the volume of biological media, microwave heating offers advantages over other heating modalities that tend to heat primarily the contacting surface. It is also possible to heat a deeper volume of tissue with more precise control using microwaves than with purely thermal conduction or RF electrode heating. Microwave Cardiac Ablation (MCA) is used to treat heart tissue that allows abnormal electrical conduction by heating it to the point of inactivation. Microwave antennas that fit within catheter systems can be positioned close to diseased tissue. Specialized antenna designs that unfurl from the catheter within the heart can then radiate specifically shaped fields, which overcome problems such as excessive surface heating at the contact point. The state of the art in MCA is reviewed in this paper and a novel catheter-based unfurling wide aperture antenna is described. This antenna consists of the centre conductor of a coaxial line, shaped into a spiral and insulated from blood and tissue by a non-conductive fluid filled balloon. Initially stretched straight inside a catheter for transluminal guiding, once in place at the cardiac target, the coiled spiral antenna is advanced into the inflated balloon. Power is applied in the range of 50-150 W at the reserved industrial, scientific and medical (ISM) frequency of 915 MHz for 30-90 s to create an irreversible lesion. The antenna is then retracted back into the catheter for removal. Simulated and experimental measurements on phantoms, in vitro animal organ tissue and living animals have shown that these microwave applicators deliver the intended therapeutic lesions that are both wider and deeper than those generated by RF ablation or other recently reported microwave applicators.
心房颤动这种常见病症通常通过切除患病的心脏组织来破坏异常的电传导通路进行治疗。利用电磁能量加热异常组织为治疗这些心律失常提供了一种微创手术替代方案。射频消融已成为许多医生的首选方法。最近，微波能量在需要精确加热生物组织的医学治疗中也显示出巨大的治疗益处。由于微波能量倾向于沉积在生物介质的整个体积中，与其他主要加热接触表面的加热方式相比，微波加热具有优势。与单纯的热传导或射频电极加热相比，使用微波还可以更精确地控制加热更深层的组织体积。微波心脏消融（MCA）用于治疗允许异常电传导的心脏组织，通过将其加热到失活点来实现。适合导管系统的微波天线可以放置在患病组织附近。然后，从心脏内的导管展开的专门天线设计可以辐射出特定形状的场，从而克服诸如接触点处过度表面加热等问题。本文综述了MCA的技术现状，并描述了一种基于导管的新型展开式宽孔径天线。该天线由同轴线的中心导体组成，形状为螺旋形，并通过充满非导电流体的气球与血液和组织绝缘。最初在导管内伸直以进行腔内引导，一旦在心脏靶点就位，盘绕的螺旋天线就推进到膨胀的气球中。在915MHz的预留工业、科学和医疗（ISM）频率下，以50 - 150W的功率施加30 - 90秒，以形成不可逆的损伤。然后将天线缩回导管以便取出。在体模、体外动物器官组织和活体动物上进行的模拟和实验测量表明，这些微波施加器产生的预期治疗损伤比射频消融或其他最近报道的微波施加器产生的损伤更宽更深。
