Thermal characteristics of non-biological vessel phantoms for treatment of varicose veins using high-intensity focused ultrasound

The ultrasonic treatment of varicose veins uses high-intensity focused ultrasound, in which a blood vessel is contracted by converting acoustic energy into thermal energy. In this study, we propose a phantom of varicose veins that can be applied for the efficient evaluation of ultrasonic treatment in varicose veins. The proposed phantom consisted of glycerol base tissue equivalent material, vessel mimic tube, and blood mimic substances. The vessel mimic tube was placed inner glycerol phantom and it was filled with blood mimic substances. Blood-mimicked substances are prepared by adjusting the concentration of the glycerol solution to be similar to the acoustic properties of the blood, and vessel-mimicking materials are selected by measuring acoustic properties and thermal shrinkage of various materials in a heat-shrinkable tube. The blood vessels surrounding the tissue are replaced with the phantom similar to glycerol-based organization, and venous blood flow is implemented using a DC motor. The heating characteristics according to the ultrasonic wave using the manufactured varicose veins phantom were evaluated. As the sound wave irradiation time and power increased, the contractility of the vessel mimicking materials and the temperature of the surrounding tissues were increased. When the blood-mimicking material was circulated, the highest temperature in the focused region and the contractility of vessel mimicking materials were reduced under the same conditions as used for sonication. The manufactured phantom may contribute to the treatment of varicose veins and can be used to predict the ultrasonic therapeutic efficiency of varicose veins.静脉曲张超声治疗采用高强度聚焦超声（high-intensity focused ultrasound），通过将声能转化为热能使血管收缩。本研究提出一款可用于静脉曲张超声治疗高效评估的静脉曲张体模（phantom）。该体模由甘油基组织等效材料、血管模拟管与血液模拟物质组成：血管模拟管置于甘油基体模内部，并填充血液模拟物质。血液模拟物质通过调节甘油溶液浓度，使其声学特性与血液相近制得；血管模拟材料则通过测量热缩管中多种材料的声学特性与热收缩性能筛选得到。本研究以该甘油基组织等效体模替代组织周边血管，并通过直流电机实现静脉血流模拟。利用制备的静脉曲张体模，评估了超声作用下的加热特性：随着声波辐照时长与功率提升，血管模拟材料的收缩率及周围组织温度均显著升高。在相同超声辐照条件下，当血液模拟物质处于循环状态时，聚焦区域的最高温度与血管模拟材料的收缩率均有所降低。本研究所制备的体模可为静脉曲张治疗提供技术支撑，并可用于预测静脉曲张的超声治疗效果。