How safe is diagnostic sonar?

Abstract

Following several reports on the possibility of harmful effects from sonar diagnosis, a detailed study has been effected to attempt to ensure the safety of clinical procedure. The emphasis in this work was with obstetric applications, such as diagnosis of pregnancy and foetal cephalometry, in which the developing foetus may be harmed. Mice were chosen as suitable experimental animals because of their large litter size, which allows good statistical analysis, and short gestation period. The range of peak ultrasonic intensities used was from 20 W cm−2 to 490 Wcm−2, mostly being well above that commonly used in clinical practice. Other dose parameters, such as time-average intensity, pulse length and total radiation time, were also vastly increased. Despite the use of these large doses no significant hazard, such as high incidence of abnormality rate, was found.