Ultrasound two main categories of biological effects commonly discussed

Ultrasound imaging is commonly thought of in association with pregnant women and images of their fetuses. Although this is true diagnostic medical ultrasound is also used for other imaging purposes all over the body. Throughout the years the procedures, protocols and equipment used during scans have become more efficient and made the process of scanning more comfortable and safe. During this time there have also been studies done to get a better insight into the effects ultrasound imaging may have on the body. Some studies were done on animals and but have taken into consideration the differences between animals and human beings to provide reliable conclusions on the possible biological effects on humans. This is possible partly due to the fact that the goal of the studies was to observe the effects of ultrasound scanning on tissues and organs not the animal as a whole. Other studies have taken a look at the results of various sources to compile their own conclusions on the effects of ultrasound imaging. The two main categories of biological effects commonly discussed among them all are the mechanical and thermal effects. According to Dalecki, “Through both thermal and nonthermal mechanisms, ultrasound can produce a variety of biological effects in tissues…”(2004). Mechanical biological effects refer to the biological effects that are produced due to mechanical forces independent of thermal effects (Shankar, 2011). Thermal biological effects are the effects on the body due to heat. The general consensus of these studies is there are very few risks associated with the routine imaging ultrasounds that are commonly performed on humans. Many of the bioeffects can be prevented during routine scans.            There are a few mechanical biological effects that have come up during studies done on ultrasound imaging. One of which is acoustic cavitation. Acoustic cavitation is “a potential biological effect of ultrasonography, marked by large-amplitude oscillations of microscopic gas bubbles” (Mosby’s Medical Dictionary, 2009).  According to Shankar, “Gas- containing structures (e.g.  ,lungs, intestines) are most susceptible to the effects of acoustic cavitation” (2011).  In addition to acoustic cavitation, “petechial hemorrhages have been seen to have developed on the mucosal surface of the intestines after ultrasound exposure although this happened at exposure at or above typical diagnostic frequencies” (Shankar, 2011). It is important to note Shankar states that this happens at exposures higher than those typically used during ultrasound scans. Although acoustic cavitation is possible it is very unlikely to happen during a routine scan. Some of the studies done have looked at the effects of ultrasound on fetuses in utero. One study showed “…the incidence of dyslexia was modestly increased in children exposed to in utero ultrasound” (Shankar, 2011). However, they go on to say that subsequent studies failed to confirm these initial findings along with other reported mechanical effects.            Thermal effects of sonography are effects on the body due to heat produced during ultrasound scans. Shankar states that “As much as 70% of the total temperature increase associated with ultrasound occurs within the first minute of exposure, but temperature does continue to rise as exposure time is prolonged”(2011). As time goes on and the machine is in continued use the transducer continues to produce a gradually increasing amount of heat. It is possible that if a scan goes on for too long that the transducer may become hot enough to become uncomfortable for the patient. There are different factors that affect the temperature produced by the transducer. “Ultrasound frequency, focusing, pulse duration, exposure time, and absorption coefficient are the primary determinants of temperature increase during ultrasound exposure” (Shankar, 2011). If all of these factors are kept low, particularly exposure time and frequency, the possible biological effects can be greatly reduced. Other things can be done to decrease any thermal effects. “Whereas ultrasound intensity and exposure duration cause direct increases in tissue temperature, a wider beam width reduces the rate and extent of temperature rise by permitting the energy to be distributed over a larger perfusion territory” (Shankar, 2011).  Despite all of the different methods to avoid thermal injury the best way to prevent it is to reduce scan time as much as possible. Although an adult may not be bothered by the initial heat produced during scanning some research shows that things may be different for fetuses. In a fetus “diagnostic ultrasound is capable of raising the temperature in fetal tissues to an extent that depend on the scanning mode, exposure duration, and tissue being scanned (2004). This source also later mentions that these results are unlikely to occur during common ultrasound scans and occurs after prolonged exposure.            Although these studies show that there are negative biological effects that are possible during ultrasound imaging there is also evidence showing how those negative biological effects can be prevented. Throughout the years ultrasound techs have come up with protocols for ultrasound scanning that takes into consideration these biological effects. These protocols help to reduce exposure time which was said to be the most important factor when considering these biological effects, particularly the thermal effects. Studies done on ultrasound and fetal tissue show that in a clinical setting today there is very little to no risk involved. The journal of ultrasound in medicine states that “There is no epidemiologic support for a causal relationship between the use of diagnostic ultrasound during pregnancy and adverse biological effects to the fetus” (2004).Based on the research done on the Biological Effects of ultrasound imaging I feel comfortable allowing myself to be scanned in the lab. I am also confident enough in the research to feel comfortable scanning on other students.