Conclusions regarding biological effects of ultrasound for diagnostically relevant exposures.

The Bioeffects Committee of the AlUM held a second AlUM Bioeffects Conference at Snowbird Resort, Utah on August 1~18, 1992 (the first AlUM Bioef· fects Conference was held at Stowe, Vermont in 1987). The conference was organized by a subcommittee consisting of Leon Frizzell (chair), Edwin Carstensen, Frederick I<remkau, Wesley Nyborg, William O'Brien, Jr., Melvin Stratmeyer, and James Zagzebski. Conference attendees included committee members and other experts on the biological effects of ultrasound. Prior to the meeting drafts were prepared of conclusions and background material regarding our current understanding of the biological effects of ultrasound. Conference attendees reworked the con· elusions and suggested changes to the extensive background documentation. After modification and approval by the Bioeffects Committee and the Board of Governors, the complete report titled "Bioeffects and Safety of Diagnostic Ultrasound" was published by the AlUM in 1993. Copies of the report may be obtained from the AlUM, 14750 Sweitzer Lane, Suite 100, Laurel, MD 20707-5906. The book is $12 for AlUM members and $24 for nonmembers. The conclusions from the report are reproduced following this introduction. They directly address the role of gas bodies and heat in the production of biological effects. In addition they provide data on the acoustic output of commercial instrumentation, describe tissue models for relating acoustic quantities measured in water to estimates of those existing in tissue, and provide a revised in vivo statement. These conclusions and supporting material contained within the report were developed primarily for the clinical user of diagnostic ultrasound, not just for scientists. The conclusions are directly relevant to essentially all areas of ultrasound, and the clinical user should become familiar with them and what they may mean for his or her specialty. The in vivo statement can assist the clinical user in putting experimental data in perspective, but it should not be misconstrued to represent safety limits for exposure during diagnostic exams. It is helpful in arriving at recommendations for wise use of ultrasound in medicine. However, the statement does not, in itself, imply specific advice on "safe levels" which might be universally valid. Determination of recommended maximum levels will require consideration of such difficult topics as: adequacy of present knowledge of bioeffects, expected reliability of equipment specifications, assessment of patient benefits, and others. The output levels of current diagnostic equipment may exceed the conditions described in the statement. In such situations, the user should be aware of alternative equipment settings and conditions which might be employed to decrease acoustic exposure.