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Figure 1. Two safety indices, thermal index and mechanical index, related to the likelihood of thermal and nonthermal effects, must be displayed on the screen of all commercially available machines.
(Figure omitted. See article PDF.)
Figure 2. MRI of the fetal brain. Fetal MRI has been used for more than 25 years and is a proven, well-established imaging modality for evaluating fetal anomalies.
(Figure omitted. See article PDF.)
Figure 3. The specific absorption rate displayed on the technical console monitor. To avoid potential risks to the fetus specific absorption rate value must not exceed 2 W/kg whole body average.
(Figure omitted. See article PDF.)
Fetal ultrasound
"Diagnostic ultrasound studies of the fetus are generally considered safe during pregnancy,"reports Practice Guideline for the Performance of Obstetric Ultrasound Examinations published by the American Institute of Ultrasound in Medicine (AIUM) in 2007. On the other hand, there are numerous publications warning that, "although diagnostic ultrasound has had an excellent safety record -laboratory studies in animals have shown serious harm if the intensity is sufficiently high"[1]. In a review of epidemiologic studies of human exposure to ultrasound, there were no effects noted on childhood cancer, dyslexia, speech development or congenital anomalies [2]. However, there is very limited evidence that the frequent exposure of the human fetus to ultrasound waves may be associated with a nonsignificant decrease in newborn body weight [3], a reduction in the frequency of right-handedness [4-6] and delayed speech [7]. What is the truth? Is fetal ultrasound totally safe, as generally considered, or do we need to be careful not to harm the fetus? The question still seems to be particularly important facing the number of fetal ultrasound scans performed worldwide [8,9]. Assuming that it was only in 2010 that the number of births all over the world was approximately 130,000,000, and in the developed countries approximately 80% of pregnant females undergo at least one ultrasound scan in pregnancy, the scale is undisputable.
What kind of potential risks to the fetus may be carried by ultrasound? Ultrasound scans may induce adverse effects by either thermal or nonthermal means. For the end user, the indices providing information on potential adverse effects are the thermal index (TI), which gives some indication of potential temperature increase and thus...