Evaluation of biological effects induced by diagnostic ultrasound in the rat foetal tissues

Abstract

In recent years, there has been growing interest in estimating the degree of heating caused by the diagnostic ultrasound in clinical practice. Both theoretical and experimental methods have been suggested for estimating the heating potential, or thermal hazard, of diagnostic ultrasound. Aim of this study was to evaluate in vivo effects of ultrasound exposure of variable duration (from 10 up to 20 min) with commercially available imaging systems commonly used for diagnostic imaging. Numerical results related to the thermal effect are obtained by simulation program based on B-mode (scanning) and Doppler (non-scanning). To investigate the biological effects of the ultrasound exposure to the brain and liver tissues, the antioxidant enzyme activity and thiobarbituric acid reactive substances (TBARS) of the tissues were evaluated. In liver tissue, as a lipid peroxidation index, TBARS levels very significantly increase in Doppler group compared to control. However, in B-mode, TBARS levels are the same with the control group. Use of B-mode in foetal tissue is more reliable than Doppler mode because temperature rise is very small compared to the Doppler mode. On the other hand, the antioxidant enzyme activities tend to increase in B-mode and Doppler groups compared to the control group as a defensive mechanism. In the brain tissue, lipid peroxidation is increased slightly in B-mode compared to the control group. This situation is related to the molecular structure of the brain tissue because of its high lipid concentration. In brain tissue, the antioxidant enzyme activities and lipid peroxidation were significantly increased, such as liver tissue in Doppler groups. Doppler ultrasound may produce harmful effects in rat foetus liver and brain tissues as a result of the high temperature rises.

Potential Adverse Ultrasound-related Biological Effects

“…Conversely, antioxidant enzyme activity decreased in the fetal brain tissue due to its higher lipid concentration after B-mode ultrasound exposure (4 MHz). 64 Interestingly, these paradoxic results were achieved with outputs within Food and Drug Administration limits. Heatshock proteins are constitutively expressed in neural cells, prevent or correct polypeptide folding, and may protect neurons against injury.…”

The Role of Ultrasound as a Diagnostic and Therapeutic Tool in Experimental Animal Models of Stroke: A Review

“…Considering these studies, the range of 12–16 MHz frequencies to be safe for imaging in the animal brain. However, other frequencies of ultrasound, such as 20 MHz, were shown to initiate cellular injury by inactivating several enzymes and causing free radical production in the brain [ 63 ], and ultrasound exposure of 3 MHz increased antioxidant enzyme activities in the rat brain [ 64 ]. Therefore, demonstrating safety at the 12–16 MHz frequency range does not directly lead to safety at lower frequencies.…”

Mechanical and Biological Effects of Ultrasound: A Review of Present Knowledge

“…In addition to the thermal effect of ultrasound, pulsed and continuous-wave ultrasound can affect reproduction and prenatal development of the embryo and fetus (Jensh and Brent 1999;Sikov 1986). Notable ultrasound effects such as increased malformation rates and weight changes have been observed in some studies, whereas others do not report any firm exposure-related effects in either dam or child (Brown et al 2004;Carnes et al 1991;Devi et al 1995;Fisher et al 1994Fisher et al , 1996Gu et al 2002;Devi 1992, 1995;Jia et al 2005;Karag€ oz et al 2007;Norton et al 1991;Oh et al 1999;Ryo et al 2001;Tarantal et al 1993). These studies used different endpoints, pregnancy ages, species and ultrasonic exposure conditions, making direct comparisons of results problematic.…”