Aoyagia Ryosuke, Nakamura Hirohumi, Azuma Takashi, Yoshinaka Kiyoshi, Takeuchi Hideki, Fujiwara Keisuke, Itani Kazunori, Sasaki Akira, Takagi Shu, Matsumoto Yoichiro
Annu Int Conf IEEE Eng Med Biol Soc. 2013;2013:6273-6. doi: 10.1109/EMBC.2013.6610987.
High intensity focused ultrasound (HIFU) treatment is one minimally invasive treatment method for cancer. Visualizing the internal treatment area of a body during HIFU treatment is required in order to achieve appropriate beam positioning and HIFU dosage. The objective of this work is to develop an ultrasound monitoring system for thermally induced coagulation. Localized motion imaging (LMI) is a monitoring method used to detect a localized mechanical response that is dependent on changes in tissue stiffness caused by thermal coagulation. In LMI, amplitude modulated HIFU causes oscillation of tissues in the HIFU focal area. The elastic modulus at a coagulated area increases and can be detected as an area with decreased oscillation amplitude., Localized control of the oscillation by changing the modulation frequency was conducted to increase the detection sensitivity for small coagulated areas in porcine liver. 2 and 7.5 MHz transducers were employed for HIFU and imaging, respectively. The amplitude modulation frequency was changed in the range from 50 to 200 Hz. The acoustic intensity of HIFU was 2.0 kW/cm2 at the focus and the exposure time was 45 s. The decrease in the amplitude of tissue oscillation at the focal point was detected within 5-10 s of HIFU exposure at the highest modulation frequency. The detected amplitude was decreased to 0.2, which indicates that for LMI, a high modulation frequency is suitable for the detection of small coagulation areas or areas of initial coagulation.
高强度聚焦超声（HIFU）治疗是一种癌症微创治疗方法。为了实现适当的波束定位和HIFU剂量，在HIFU治疗期间需要可视化身体的内部治疗区域。这项工作的目的是开发一种用于热诱导凝固的超声监测系统。局部运动成像（LMI）是一种监测方法，用于检测依赖于热凝固引起的组织硬度变化的局部机械响应。在LMI中，调幅HIFU会导致HIFU焦点区域的组织振荡。凝固区域的弹性模量增加，可以检测为振荡幅度减小的区域。通过改变调制频率对振荡进行局部控制，以提高对猪肝中小凝固区域的检测灵敏度。分别使用2MHz和7.5MHz的换能器进行HIFU和成像。调制频率在50至200Hz范围内变化。HIFU在焦点处的声强为2.0kW/cm2，暴露时间为45秒。在最高调制频率下，HIFU暴露5至10秒内即可检测到焦点处组织振荡幅度的降低。检测到的幅度降至0.2，这表明对于LMI，高调制频率适用于检测小凝固区域或初始凝固区域。
