Percutaneous cardiac HIFU ablation with multimodal image guidance

描述（由申请人提供）：心房颤动（AF）是最常见的心律失常类型，在一般人群中估计患病率为0.4%至1%，随着年龄的增长而增加（80岁以上人群为8%）。除药物治疗外，基于电生理的治疗方式，如消融治疗被广泛用于心律失常。治疗房颤最常见的解剖目标是肺静脉入口及其周围组织。目前，射频（RF）能量通常用于消融心脏中所描述的部位。使用射频消融术很难控制消融模式，在产生深部病变方面也有局限性。如果不能实现心脏组织的完全电隔离，则复发的可能性很大。高强度聚焦超声（HIFU）方法最近被尝试用于肺静脉隔离，主要是为了创造深度和可控的消融模式。然而，这些尝试由于缺乏直接的成像指导而遭受损失，因此对膈神经和食道等周围组织造成附带损伤。射频消融方法众所周知的缺点和早期HIFU结果所呈现的局限性清楚地表明，需要一种将图像引导与有效和良好控制的消融方法相结合的系统。我们建议开发设备和系统来解决总结的问题。在我们提出的方案中，常规超声成像用于解剖指导和目标识别，HIFU用于组织消融，光声成像用于监测病变形成。该装置基于电容式微机械超声换能器技术。与具有高内部介电损耗的压电器件不同，cmut在连续波工作中具有最小的自热。这种压电换能器的自热是早期心脏HIFU尝试中所经历的附带损伤的部分原因。CMUTs也可以在适合双重成像/治疗操作的大型阵列中实现。提出的工作具体目标如下：1)开发用于初步可行性研究的大型原型（15mm占地面积）CMUT阵列，以及临床适用的小型（7mm占地面积）CMUT阵列，集成支持前端电路和后端系统，能够结合超声和光声成像进行HIFU输送。2)利用系统子组件对离体组织样本和体内开胸、开大腿动物模型进行初步可行性研究，确定HIFU消融和光声成像的最佳参数。3)在猪模型中进行心脏研究，使用小型化集成探头（占地7毫米），利用封闭的胸部，微创模型通过肋间隙的小切口插入探头。

DESCRIPTION (provided by applicant): Atrial fibrillation (AF) is the most common type of cardiac arrhythmia, with an estimated prevalence of 0.4% to 1% in the general population, increasing with age (8% for people over 80). In addition to drug treatments, electrophysiology-based treatment modalities such as ablation treatment are wide employed for arrhythmias. To treat the AF the most common anatomical target for ablation is the entrance of pulmonary veins and the surrounding tissue. Currently, radio-frequency (RF) energy is generally used to ablate the described sites in the heart. It is difficult to control the ablation pattern using RF ablation which also has limitations in creating deep lesions. If the total electrical isolation in cardiac tissue cannot be achieved, recurrence becomes highly likely. High-intensity focused ultrasound (HIFU) methods have been attempted lately for pulmonary vein isolation, mainly motivated by the promise of creating deep and controlled ablation patterns. However, these attempts suffered from a lack of direct imaging guidance and consequently collateral damage in surrounding tissues such as the phrenic nerve and the esophagus. The well-known shortcomings of RF ablation methods and the limitations presented by the early HIFU results clearly indicate the need for a system that integrates image guidance with effective and well-controlled ablation methods. We propose to develop devices and systems to address the summarized issues. In our proposed scheme, conventional ultrasound imaging is used for anatomical guidance and target identification, HIFU for tissue ablation, and photoacoustic imaging for monitoring lesion formation. The proposed device is based on the capacitive micromachined ultrasonic transducer (CMUT) technology. CMUTs are proven to have minimal self-heating in continuous wave operation, unlike their piezoelectric counterparts with high internal dielectric losses. This self-heating of piezoelectric transducers was partly responsible for the collateral damage experienced in early cardiac HIFU attempts. CMUTs can also be implemented in large arrays that are suitable for dual imag- ing/therapeutic operation. The specific aims of the proposed work are as follows: 1) Develop a large-scale prototype (15-mm footprint) CMUT array for use in initial feasibility studies and a clinically suitable, small-scale (7-mm footprint) CMUT array integrated with supporting frontend circuits and backend systems, capable of HIFU delivery combined with ultrasound and photoacoustic imaging. 2) Conduct initial feasibility studies on ex-vivo tissue samples and in-vivo open-chest and open-thigh animal models using system subcomponents to determine optimal parameters for both HIFU ablation and photoacoustic imaging. 3) Conduct cardiac studies in the porcine model utilizing the miniaturized integrated probe (7-mm footprint) utilizing a closed chest, minimally invasive model for insertion of the probe through a small incision through the intercostal space.