Barnett S B, Rott H D, ter Haar G R, Ziskin M C, Maeda K
Ultrasonics Laboratory, CSIRO, Chatswood, Australia.
Ultrasound Med Biol. 1997;23(6):805-12. doi: 10.1016/s0301-5629(97)00027-6.
Mammalian tissues have differing sensitivities to damage by physical agents such as ultrasound. This article evaluates the scientific data in terms of known physical mechanisms of interaction and the impact on pre- and postnatal tissues. Actively dividing cells of the embryonic and fetal central nervous system are most readily disturbed. As a diagnostic ultrasound beam envelopes a small volume of tissue, it is possible that the effects of mild disturbance may not be detected unless major neural pathways are involved. There is evidence that ultrasound can be detected by the central nervous system; however, this does not necessarily imply that the bioeffect is hazardous to the fetus. Biologically significant temperature increases can occur at or near to bone in the fetus from the second trimester, if the beam is held stationary for more than 30 s in some pulsed Doppler applications. In this way, sensory organs that are encased in bone may be susceptible to heating by conduction. Reports in animals and humans of retarded growth and development following frequent exposures to diagnostic ultrasound, in the absence of significant heating, are difficult to explain from the current knowledge of ultrasound mechanisms. There is no evidence of cavitation effects occurring in the soft tissues of the fetus when exposed to diagnostic ultrasound; however, the possibility exists that such effects may be enhanced by the introduction of echo-contrast agents.
哺乳动物组织对超声等物理因素造成的损伤具有不同的敏感性。本文根据已知的相互作用物理机制以及对产前和产后组织的影响来评估科学数据。胚胎和胎儿中枢神经系统中活跃分裂的细胞最容易受到干扰。由于诊断超声束包围着一小部分组织，除非涉及主要神经通路，否则轻度干扰的影响可能无法检测到。有证据表明中枢神经系统能够检测到超声；然而，这并不一定意味着这种生物效应会对胎儿有害。在某些脉冲多普勒应用中，如果波束在胎儿骨骼处或其附近静止超过30秒，从孕中期开始胎儿骨骼处或其附近可能会出现具有生物学意义的温度升高。这样一来，包裹在骨骼中的感觉器官可能会因传导而易于受热。在没有明显发热的情况下，动物和人类频繁接触诊断超声后出现生长发育迟缓的报告，从目前对超声机制的了解来看很难解释。没有证据表明胎儿软组织在暴露于诊断超声时会发生空化效应；然而，引入超声造影剂可能会增强这种效应。
