Nau W H, Diederich C J, Burdette E C
Department of Radiation Oncology, University of California, San Francisco 94143-0226, USA.
Med Phys. 2001 Jul;28(7):1525-34. doi: 10.1118/1.1381550.
Catheter-cooled (CC) interstitial ultrasound applicators were evaluated for their use in high-temperature coagulative thermal therapy of tissue. Studies in ex vivo beef muscle were conducted to determine the influences of applied electrical power levels (5-20 W per element), catheter flow rate (20-60 ml min(-1)), circulating water temperature (7-40 degrees C), and frequency (7-9 MHz) on temperature distribution and thermal lesion geometry. The feasibility of using multiple interstitial applicators to thermally coagulate a predetermined volume of tissue was also investigated. Results of these studies revealed that the directional shape of the thermal lesions is maintained with increasing time and power. Radial depths of the thermal lesions ranged from 10.7 +/- 0.7 mm after heating for 4 min with an applied power level of 5 W, to 16.2 +/- 1.4 mm with 20 W. The axial length of the thermal lesions is controlled tightly by the number of active transducers. A catheter flow rate of 20 to 40 ml min(-1) (52.2 +/- 5.5 kPa at 40 ml min(-1)) with 22 degrees C water was determined to provide sufficient cooling of the transducers for power levels used in this study. In vivo temperatures measured in the center of a 3-cm-diam peripheral implant of four applicators in pig thigh muscle reached 89.3 degrees C after 4 min of heating, with boundaries of coagulation clearly defined by applicator position and directivity. Conformability of heating in a clinically relevant model was demonstrated by inserting two directional CC applicators with a 2 cm separation within an in vivo canine prostate, and generating a thermal lesion measuring 3.8 cm x 2.2 cm in cross section while directing energy away from, and protecting the rectum. Maximum measured temperatures at midgland exceeded 90 degrees C within 20 min of heating. The results of this study demonstrate the utility of single or multiple CC applicators for conformal thermal coagulation and high temperature thermal therapy, with potential for clinical applications in sites such as prostate, liver, breast, or uterus.
对导管冷却（CC）组织间超声探头在组织高温凝固热疗中的应用进行了评估。在离体牛肉肌肉中进行了研究，以确定施加的电功率水平（每个元件5 - 20 W）、导管流速（20 - 60 ml min⁻¹）、循环水温（7 - 40℃）和频率（7 - 9 MHz）对温度分布和热损伤几何形状的影响。还研究了使用多个组织间探头对预定体积的组织进行热凝固的可行性。这些研究结果表明，随着时间和功率的增加，热损伤的定向形状得以保持。热损伤的径向深度范围为：施加功率水平为5 W加热4分钟后为10.7±0.7 mm，20 W时为16.2±1.4 mm。热损伤的轴向长度由有源换能器的数量严格控制。确定在水温22℃时，20至40 ml min⁻¹（40 ml min⁻¹时为52.2±5.5 kPa）的导管流速可为该研究中使用的功率水平的探头提供足够的冷却。在猪大腿肌肉中植入四个探头形成直径3 cm的外周植入物，加热4分钟后，其中心部位的体内温度达到89.3℃，凝固边界由探头位置和方向性清晰界定。通过在犬体内前列腺内插入两个间距为2 cm的定向CC探头，并在将能量导向远离直肠并保护直肠的同时产生横截面尺寸为3.8 cm×2.2 cm的热损伤，证明了在临床相关模型中加热的适形性。加热20分钟内，腺体中部测得的最高温度超过90℃。本研究结果证明了单个或多个CC探头在适形热凝固和高温热疗中的实用性，在前列腺、肝脏、乳腺或子宫等部位具有临床应用潜力。
