Fetal Thermal Effects of Diagnostic Ultrasound

Abstract

rocesses that can produce a biological effect with some degree of heating (ie, about 1°C above the physiologic temperature) act via a thermal mechanism. Investigations with laboratory animals have documented that pulsed ultrasound can produce elevations of temperature and damage in biological tissues in vivo, particularly in the presence of bone (intracranial temperature elevation). Acoustic outputs used to induce these adverse bioeffects are within the diagnostic range, although exposure times are usually considerably longer than in clinical practice. Conditions present in early pregnancy, such as lack of perfusion, may favor bioeffects. Thermally induced teratogenesis has been shown in many animal studies, as well as several controlled human studies; however, human studies have not shown a causal relationship between diagnostic ultrasound exposure during pregnancy and adverse biological effects to the fetus. All human epidemiologic studies, however, were conducted with commercially available devices predating 1992, that is, with acoustic outputs not exceeding a spatial-peak temporal-average intensity of 94 mW/cm 2 . Current limits in the United States allow a spatial-peak temporal-average intensity of 720 mW/cm 2 for fetal applications. The synergistic effect of a raised body temperature (febrile status) and ultrasound insonation has not been examined in depth. Available evidence, experimental or epidemiologic, is insufficient to conclude that there is a causal relationship between obstetric diagnostic ultrasound exposure and obvious adverse thermal effects to the fetus. However, very subtle effects cannot be ruled out and indicate a need for further research, although research in humans may be extremely difficult to realize.

Effects of diagnostic ultrasound on HSP70 expression in chorionic villi in rats during early pregnancy and the role of HSP70 in apoptosis in chorionic villi

“…A study on human chorionic villi indicated that the cleavage products of active caspase-3 and cytochrome c release were significantly increased in a time-dependent manner when exposed to transvaginal ultrasound in the first trimester of pregnancy (14). Moreover, the degree of damage diagnostic ultrasound has on the embryo differ at various developmental stages and tissues, in which embryo pre-implantation and the nervous system are the most sensitive stage and tissue, respectively (2,15,16).…”

Safety Practices of Sonographers and Their Knowledge of the Biologic Effects of Sonography

“…The correct answer to this question was in the first and third trimesters. [13][14][15][16] Therefore, any combination of answers, which included at least one of the two answers, was given a score of 0.5. If neither answer was selected, a score of zero was given.…”

Knowledge of Togolese Doctors on Biological Effects of Ultrasound and Their Attitudes towards the Ultrasonographic Explorations Performed in Lome (Togo)

“…In fact, the TI evaluate the risk of thermic effect occurring and the MI the mechanic one. The thermic effect is shown by a temperature increase due to the transformation of acoustic energy of ultrasound in thermic energy [11]. The ultrasounds can provoke tissue heating of some Celsius degrees.…”