Jensh R P, Lewin P A, Poczobutt M T, Goldberg B B, Oler J, Brent R L
Department of Anatomy, Jefferson Medical College of Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
Radiat Res. 1994 Nov;140(2):284-93.
The examination of pregnant women using diagnostic ultrasound has increased greatly over past decades in the United States. As sonography techniques have been altered and refined, there has been renewed interest concerning possible effects on the developing fetus, since exposures in mid-gestation occur during the sensitive period of brain development. The present study is concerned with possible neonatal functional deficits due to exposure of the fetus to ultrasound. An ultrasound exposure tank was designed specifically for controlled studies of bioeffects. Thirty-six pregnant rats were anesthetized, immersed to the axilla in a water tank and exposed on the 15th, 17th and 19th days of gestation. Twelve rats were exposed to 5.0 MHz pulsed ultrasound of effective pulse duration equal to approximately 0.170 microseconds, pulse repetition rate 1 kHz, and a spatial peak, temporal peak intensity (ISPTP) of 500 W/cm2, representing a clinically relevant exposure level. The spatial peak, pulse average intensity (ISPPA), spatial peak temporal average intensity (ISPTA) and maximum intensity (Im) were determined to be 100 W/cm2, 24 mW/cm2 and 230 W/cm2, respectively. The maximum rarefaction pressure, pr, was measured as 12.5 x 10(5) Pa, and the total power was 2.5 mW. Twelve other rats were exposed to 1500 W/cm2, ISPTP (ISPPA, 350 W/cm2; ISPTA, 58 mW/cm2; Im, 600 W/cm2). Twelve additional rats were sham-exposed. Since the focal area was about 0.5 cm2, computer-controlled stepper motors moved the rats through the ultrasound field to assure uniform exposure of the abdominal/pelvic region. Total exposure time was 35 min. Additionally, a miniature thermocouple was implanted in a few rats to verify that no significant increase in body temperature took place during exposure. All neonates were subjected to five reflex tests and observed for four physiological parameters. Postnatal growth also was monitored. Analyses of the data indicate there were no significant alterations in neonatal development or postnatal growth due to exposure to 5.0 MHz ultrasound below an intensity (ISPTP) of 1500 W/cm2. Studies continue to be completed at higher exposure levels to determine the margin of safety, and the animals will continue to be monitored and evaluated through young adulthood to determine if there are long-term behavioral effects due to fetal exposure to ultrasound.
在美国，过去几十年间，使用诊断性超声对孕妇进行检查的情况大幅增加。随着超声检查技术的改变与完善，人们对其可能对发育中的胎儿产生的影响重新产生了兴趣，因为孕中期的暴露发生在大脑发育的敏感期。本研究关注的是胎儿暴露于超声后可能出现的新生儿功能缺陷。专门设计了一个超声暴露槽用于生物效应的对照研究。36只怀孕大鼠被麻醉后，将其腋窝以下部位浸入水槽，并在妊娠第15、17和19天进行暴露。12只大鼠暴露于频率为5.0 MHz的脉冲超声，有效脉冲持续时间约为0.170微秒，脉冲重复频率为1 kHz，空间峰值、时间峰值强度（ISPTP）为500 W/cm²，这代表了临床相关的暴露水平。空间峰值、脉冲平均强度（ISPPA）、空间峰值时间平均强度（ISPTA）和最大强度（Im）分别测定为100 W/cm²、24 mW/cm²和230 W/cm²。最大稀疏压力pr测量为12.5×10⁵ Pa，总功率为2.5 mW。另外12只大鼠暴露于1500 W/cm²的ISPTP（ISPPA为350 W/cm²；ISPTA为58 mW/cm²；Im为600 W/cm²）。还有12只大鼠进行假暴露。由于聚焦区域约为0.5 cm²，计算机控制的步进电机将大鼠移动通过超声场，以确保腹部/盆腔区域均匀暴露。总暴露时间为35分钟。此外，在几只大鼠体内植入了微型热电偶，以验证暴露期间体温没有显著升高。所有新生大鼠都接受了五项反射测试，并观察了四项生理参数。还监测了出生后的生长情况。数据分析表明，暴露于强度（ISPTP）低于1500 W/cm²的5.0 MHz超声下，新生大鼠的发育或出生后的生长没有显著变化。仍在继续完成更高暴露水平的研究以确定安全边际，并且这些动物将在成年前继续接受监测和评估，以确定胎儿暴露于超声是否存在长期行为影响。
