he potential importance of ultrasound-induced bioeffects in the context of patient imaging is an important and as of yet unresolved matter. Although there is no question that the introduction of acoustic energy into a patient has the potential to induce a biological response, the specific mechanisms involved and the underlying physics of energy transfer in a complex biological medium such as tissue remain under investigation. Although there are reports in the scientific literature of observable effects in animal and tissue culture models, reproducible data regarding the response of humans to ultrasound exposure are more difficult to find. Certainly, ultrasound is used for therapeutic applications involving hyperthermia, so it is obvious that at sufficiently high levels a biological effect can be produced. Thus, the dilemma arises: what level is high enough to produce an observable effect? This situation is further complicated by the definition of what the observable effect is. Although heating and charring of tissue is certainly an observable effect, there are other effects occurring primarily on the microscopic, cellular, or subcellular level. Additionally, some effects may not be morphologic but represent alterations in cellular metabolism, blood flow, or neurologic function. There is active research under way trying to elucidate these questions. As results are published in the peer-reviewed literature, we gain a broader overview of the relative risk and potential for harm. It is important that published findings be repeatable and comprehensible in the larger context of previous work. Additionally, it is important that published study designs clearly indicate what was measured and how, so others may both benefit from the results and place them into a reasonable perspective of assessing the importance of the findings. Such precision in information is particularly challenging in the ultrasound bioeffects arena. Although the basic physics of ultrasound interaction are reasonably well understood in simple models, the complexity of biological tissues leaves current models wanting. Well-equipped laboratories having all manner of instrumentation may be hard pressed to make measurements of sufficient precision to accurately reflect true energy deposition and mechanical effects. A greater challenge exists for less well-equipped laboratories having more limited measurement resources. The situation is even more daunting for clinical imaging facilities conducting research involving their human patients for whom a biological effect is observed or a longitudinal study is designed to detect possible effects. Current ultrasonic scanners provide very limited information regarding energy transfer and deposition. In part, this is because such information is hard to come by in a particular experimental configuration or patient from returning echo intensity information. Furthermore, this is complicated by the complexity and nuances of how acoustic energy interacts with the patient in the first place. Because the underlying tissue is heterogeneous, accurate estimation of energy deposition is difficult, particularly when accommo-