Kinsey Adam M, Diederich Chris J, Tyreus P Daniel, Nau William H, Rieke Viola, Pauly Kim Butts
Thermal Therapy Research Group, Department of Radiation Oncology, University of California, San Francisco, California 94115-1708, USA.
Med Phys. 2006 May;33(5):1352-63. doi: 10.1118/1.2184443.
Dynamic angular control of thermal ablation and hyperthermia therapy with current interstitial heating technology is limited in capability, and often relies upon nonadjustable angular power deposition patterns and/or mechanical manipulation of the heating device. The objective of this study was to investigate the potential of multisectored tubular interstitial ultrasound devices to provide control of the angular heating distribution without device manipulation. Multisectored tubular transducers with independent sector power control were incorporated into modified versions of internally cooled (1.9 mm OD) and catheter-cooled (2.4 mm OD) interstitial ultrasound applicators in this work. The heating capabilities of these multisectored devices were evaluated by measurements of acoustic output properties, measurements of thermal lesions produced in ex vivo tissue samples, biothermal simulations of thermal ablation and hyperthermia treatments, and MR temperature imaging of ex vivo and in vivo experiments. Acoustic beam measurements of each applicator type displayed a 35 degrees -40 degrees acoustic dead zone between each independent sector, with negligible mechanical or electrical coupling. Thermal lesions produced in ex vivo liver tissue with one, two, or three sectors activated ranged from 13-18 mm in radius with contiguous zones of coagulation between active sectors. The simulations demonstrated the degree of angular control possible by using variable power levels applied to each sector, variable duration of applied constant power to individual sectors, respectively, or a multipoint temperature controller to vary the power applied to each sector. Despite the acoustic dead zone between sectors, the simulations also showed that the variance from the maximum lesion radius with three elements activated is within 4%-13% for tissue perfusions from 1-10 kg m(-3) s(-1). Simulations of hyperthermia with maximum tissue temperatures of 45 degrees C and 48 degrees C displayed radial penetration up to 2 cm of the 40 degrees C steady-state contour. Thermal characterizations of trisectored applicators in ex vivo and in vivo muscle, using real-time MR thermal imaging, reinforced angular controllability and negligible radial variance of the heating pattern from the applicators, demonstrated effective heating penetration, and displayed MR compatibility. The multisectored interstitial ultrasound applicators developed in this study demonstrated a significant degree of dynamic angular control of a heating pattern without device manipulation, while maintaining heat penetration consistent with previously reported results from other interstitial ultrasound applicators.
利用当前的间质加热技术对热消融和热疗进行动态角度控制的能力有限，并且通常依赖于不可调节的角度功率沉积模式和/或加热设备的机械操作。本研究的目的是探讨多扇区管状间质超声设备在不进行设备操作的情况下控制角度加热分布的潜力。在这项工作中，将具有独立扇区功率控制的多扇区管状换能器集成到内部冷却（外径1.9毫米）和导管冷却（外径2.4毫米）间质超声 applicator 的改进版本中。通过测量声学输出特性、测量离体组织样本中产生的热损伤、热消融和热疗的生物热模拟以及离体和体内实验的磁共振温度成像，评估了这些多扇区设备的加热能力。每种 applicator 类型的声束测量显示，每个独立扇区之间存在35度 - 40度的声学盲区，机械或电耦合可忽略不计。在离体肝组织中，激活一个、两个或三个扇区产生的热损伤半径在13 - 18毫米之间，活跃扇区之间有连续的凝固区域。模拟结果表明，通过分别对每个扇区施加可变功率水平、对单个扇区施加恒定功率的可变持续时间或使用多点温度控制器来改变施加到每个扇区的功率，可以实现角度控制的程度。尽管扇区之间存在声学盲区，但模拟结果还表明，对于1 - 10 kg m(-3) s(-1)的组织灌注，激活三个元件时与最大损伤半径的偏差在4% - 13%以内。对最高组织温度为45摄氏度和48摄氏度的热疗模拟显示，40摄氏度稳态轮廓的径向穿透深度可达2厘米。使用实时磁共振热成像对离体和体内肌肉中的三分扇区 applicator 进行热特性分析，增强了加热模式的角度可控性和可忽略不计的径向偏差，证明了有效的加热穿透，并显示出磁共振兼容性。本研究中开发的多扇区间质超声 applicator 在不进行设备操作的情况下，对加热模式具有显著程度的动态角度控制，同时保持与先前其他间质超声 applicator 报道结果一致的热穿透。
