Deardorff D L, Diederich C J
TxSonics, Inc., Hartland, WI 53029, USA.
IEEE Trans Ultrason Ferroelectr Freq Control. 2000;47(1):170-8. doi: 10.1109/58.818759.
A multi-element, direct-coupled ultrasound (US) applicator with internal water cooling was investigated for axial control of interstitial thermal coagulation. A prototype implantable applicator was constructed with a linear array of three tubular PZT ultrasound transducers (each 2.5 mm OD, 10 mm length, 360 degrees emittance). Acoustic beam distributions from each element were measured and found to be collimated within the transducer length. The internally cooled applicator could sustain high levels of applied power to each transducer (0 to 40 W) and maintain acceptable applicator surface temperatures (<100 degrees C). Thermal performance of the applicator was investigated through heating trials in vivo (porcine thigh muscle and liver) and in vitro (bovine liver). The radial depth of thermal lesions produced was dependent on the applied power and sonication time and was controlled independently with power levels to each transducer element. With 18 W per element (applied electrical power) for 3 min, cylindrical thermal lesions were produced with a diameter of 3 cm and a length ranging from 1.2 cm (with one element) to 3.5 cm (three elements). Higher powers (24 to 30 W) for 3 to 5 min provided increased depths of coagulation (4 cm diameter lesions). Analysis of axial lesion shapes demonstrated that individual variation of power to each transducer element provided control of axial heating and depth of coagulation (for custom lesion shapes); lesion lengths corresponded to the number of active transducers. This ability to control the heating distribution dynamically along the length of the applicator has potential for improved target localization of thermal coagulation and necrosis in high temperature thermal therapy.
研究了一种带有内部水冷装置的多元素直接耦合超声（US）施加器，用于间质热凝固的轴向控制。构建了一个原型可植入式施加器，它由三个管状压电超声换能器的线性阵列组成（每个外径2.5毫米，长度10毫米，360度发射角）。测量了每个元件的声束分布，发现其在换能器长度范围内是准直的。内部冷却的施加器能够维持施加到每个换能器的高功率水平（0至40瓦），并保持施加器表面温度在可接受范围内（<100摄氏度）。通过在体内（猪大腿肌肉和肝脏）和体外（牛肝脏）的加热试验研究了该施加器的热性能。产生的热损伤的径向深度取决于施加的功率和超声处理时间，并可通过对每个换能器元件的功率水平独立控制。每个元件施加18瓦（施加电功率）持续3分钟，产生了直径约3厘米、长度范围从1.2厘米（一个元件）到3.5厘米（三个元件）的圆柱形热损伤。更高的功率（24至30瓦）持续3至5分钟可增加凝固深度（直径约4厘米的损伤）。对轴向损伤形状的分析表明，对每个换能器元件的功率进行单独变化可控制轴向加热和凝固深度（用于定制损伤形状）；损伤长度与有源换能器的数量相对应。这种沿着施加器长度动态控制加热分布的能力在高温热疗中对于改善热凝固和坏死的目标定位具有潜力。
