Ahmadi Farzaneh, McLoughlin Ian Vince
Annu Int Conf IEEE Eng Med Biol Soc. 2013;2013:1964-7. doi: 10.1109/EMBC.2013.6609913.
Low frequency ultrasound has a diverse set of industrial and medical applications ranging from high power industrial ultrasound equipment through to various therapeutic medical applications. In recent years, several speech interface applications have also been developed which exploit the low ultrasonic frequency region to augment human-computer interfacing. These devices tend to operate just above the threshold of human hearing where signals can be generated and detected using off-the-shelf audio hardware components. Mechanical index has long been one of the main criteria used for determining safety limits for human exposure to ultrasound, however it is known to be inaccurate below about 500 kHz. This paper revisits the mathematical and physical foundations of the mechanical index, in particular transient cavitation, and applies these to the low-frequency ultrasound region. Simulations are performed to evaluate the effects on both blood and water. From the results, a new mechanical index formulation is proposed, which extends down to significantly lower frequencies. The aim is to provide a gauge for determining bio-effects of emerging and future low frequency ultrasonic applications operating around 20 kHz to 100 kHz.
低频超声有一系列不同的工业和医学应用，从高功率工业超声设备到各种治疗性医学应用。近年来，还开发了几种语音接口应用，这些应用利用低超声频率区域来增强人机交互。这些设备往往在略高于人类听力阈值的频率下运行，在这个频率范围内可以使用现成的音频硬件组件来生成和检测信号。长期以来，机械指数一直是确定人类超声暴露安全限度的主要标准之一，然而已知在约500kHz以下它并不准确。本文重新审视了机械指数的数学和物理基础，特别是瞬态空化，并将其应用于低频超声区域。进行了模拟以评估对血液和水的影响。根据结果，提出了一种新的机械指数公式，该公式可延伸到显著更低的频率。目的是为确定围绕20kHz至100kHz运行的新兴和未来低频超声应用的生物效应提供一种衡量标准。
