Tyréus Per Daniel, Nau William H, Diederich Chris J
Thermal Therapy Research Group, Radiation Oncology Department, UCSF Mt. Zion Cancer Center, San Francisco, California 94115, USA.
Med Phys. 2003 Jul;30(7):1855-63. doi: 10.1118/1.1584125.
High temperature ultrasound thermal therapy using interstitial and external approaches is becoming increasingly acceptable as a minimally invasive clinical treatment for cancerous and benign disease. The diameter of an interstitial applicator can influence its clinical practicality and effectiveness as well as application site. The purpose of this study was to determine whether the use of larger ultrasound transducers and the inherent increase in applicator size could be justified by potentially producing larger lesion diameters. Four applicator configurations and sizes were studied using ex vivo tissue experiments in liver and beef and using acoustic and biothermal simulations. Catheter-cooled and internally cooled applicators with outer diameters between 2.2 and 4.0 mm produced 3.5 to 5.0 cm diameter lesions in ex vivo liver and 3.0 to 3.5 cm lesions in ex vivo beef muscle with 20-40 W/cm applied for 10 min. Larger applicators produced lesions with radial penetration depths superior to their smaller counterparts at power levels in the 20-40 W/cm range. The higher cooling rates along the outer surface of the larger diameter applicators due to their greater surface area was a dominant factor in increasing lesion size. The higher cooling rates pushed the maximum temperature farther from the applicator surface and reduced the formation of high acoustic attenuation tissue zones. Applicator configuration and frequency (6.7-8.2 MHz) had less influence on lesion size than diameter in the ranges studied. Acoustic and biothermal simulations matched the experimental data well and were applied to model these applicators within sites of clinical interest such as prostate, uterine fibroid, brain, and normal liver. Lesions of 3.9 to 4.7 cm diameter were predicted for moderately perfused tissues such as prostate and fibroid and 2.8 to 3.2 cm for highly perfused tissues such as normal liver. In sites such as uterine fibroid where larger applicators placed using an endoscopic approach could be tolerated, treatment volume increases of 37% were predicted for an applicator diameter increase from 2.4 to 4.0 mm.
使用间质和外部方法的高温超声热疗法作为一种针对癌症和良性疾病的微创临床治疗方法正越来越被接受。间质施源器的直径会影响其临床实用性、有效性以及应用部位。本研究的目的是确定使用更大的超声换能器以及施源器尺寸的固有增加是否能通过潜在地产生更大的病变直径而得到合理证明。使用肝脏和牛肉组织的离体实验以及声学和生物热模拟研究了四种施源器配置和尺寸。外径在2.2至4.0毫米之间的导管冷却式和内部冷却式施源器，在离体肝脏中产生了直径为3.5至5.0厘米的病变，在离体牛肉肌肉中产生了直径为3.0至3.5厘米的病变，施加20 - 40瓦/平方厘米的功率持续10分钟。在20 - 40瓦/平方厘米的功率水平下，较大的施源器产生的病变其径向穿透深度优于较小的施源器。由于较大直径施源器的表面积更大，其外表面的冷却速率更高，这是增加病变尺寸的一个主导因素。更高的冷却速率将最高温度推离施源器表面，并减少了高声衰减组织区域的形成。在所研究的范围内，施源器配置和频率（6.7 - 8.2兆赫兹）对病变尺寸的影响小于直径。声学和生物热模拟与实验数据匹配良好，并被应用于对前列腺、子宫肌瘤、脑和正常肝脏等临床感兴趣部位的这些施源器进行建模。对于中等灌注组织如前列腺和肌瘤，预测病变直径为3.9至4.7厘米，对于高灌注组织如正常肝脏，预测病变直径为2.8至3.2厘米。在子宫肌瘤等部位，使用内窥镜方法放置较大的施源器是可以耐受的，预计施源器直径从2.4毫米增加到4.0毫米时，治疗体积将增加37%。
