Miller Douglas L
Department of Radiology, University of Michigan, Ann Arbor, MI 48109-0553, USA.
Semin Ultrasound CT MR. 2008 Apr;29(2):156-64. doi: 10.1053/j.sult.2007.12.003.
Safety assurance for diagnostic ultrasound in obstetrics began with a tacit assumption of safety allowed by a federal law enacted in 1976 for then-existing medical ultrasound equipment. The implementation of the 510(k) pre-market-approval process for diagnostic ultrasound resulted in the establishment of guideline upper limits for several examination categories in 1985. The obstetrical category has undergone substantial evolution from initial limits (ie, 46 mW/cm2 spatial peak temporal average [SPTA] intensity) set in 1985. Thermal and mechanical exposure indices, which are displayed onscreen according to an Output Display Standard, were developed for safety assurance with relaxed upper limits. In 1992, with the adoption of the Output Display Standard, the allowable output for obstetrical ultrasound was increased in terms of both the average exposure (eg, to a possible 720 mW/cm2 SPTA intensity) and the peak exposure (via the Mechanical Index). There has been little or no subsequent research with the modern obstetrical ultrasound machines to systematically assess potential risks to the fetus using either relevant animal models of obstetrical exposure or human epidemiology studies. The assurance of safety for obstetrical ultrasound therefore is supported by three ongoing means: (1) review of a substantial but uncoordinated bioeffect research literature; (2) the theoretical evaluation of diagnostic ultrasound exposure in terms of thermal and nonthermal mechanisms for bioeffects; and (3) the skill and knowledge of professional sonographers. At this time, there is no specific reason to suspect that there is any significant health risk to the fetus or mother from exposure to diagnostic ultrasound in obstetrics. This assurance of safety supports the prudent use of diagnostic ultrasound in obstetrics by trained professionals for any medically indicated examination.
产科诊断超声的安全保障始于1976年颁布的一项联邦法律对当时现有医用超声设备所默认的安全假设。1985年，诊断超声510(k)上市前批准程序的实施，导致为几个检查类别确立了指导上限。产科类别的上限自1985年设定的初始限制（即46毫瓦/平方厘米空间峰值时间平均[SPTA]强度）以来经历了重大演变。根据输出显示标准在屏幕上显示的热暴露和机械暴露指数，是为了在放宽上限情况下进行安全保障而制定的。1992年，随着输出显示标准的采用，产科超声的允许输出在平均暴露（例如，可能达到720毫瓦/平方厘米SPTA强度）和峰值暴露（通过机械指数）方面都有所增加。对于现代产科超声机器，几乎没有后续研究使用相关的产科暴露动物模型或人类流行病学研究来系统评估对胎儿的潜在风险。因此，产科超声的安全保障通过三种持续的方式得到支持：(1) 对大量但不协调的生物效应研究文献进行审查；(2) 根据生物效应的热机制和非热机制对诊断超声暴露进行理论评估；(3) 专业超声检查人员的技能和知识。目前，没有具体理由怀疑产科诊断超声暴露会对胎儿或母亲造成任何重大健康风险。这种安全保障支持经过培训的专业人员在产科为任何医学指征检查谨慎使用诊断超声。
