title: Section 7--discussion of the mechanical index and other exposure parameters. American Institute of Ultrasound in Medicine.
abstract: There have been long-term efforts to identify a threshold pressure for the onset of inertial cavitation under conditions relevant to ultrasound in medicine. Before the introduction of the output display standard [AIUM/NEMA, 1992a], quantities such as the spatial peak pulse average intensity (I(SPPA)), and, earlier, Im, the spatial peak intensity averaged over the largest half-cycle, were used to give a measure of the potential of a cavitation-based bioeffect due to an acoustic field. Relatively early in the Output Display Standard development effort, the Food and Drug Administration indicated a need for a superior indicator for the potential for cavitation-related bioeffects, initiating a search for such an index. The following paragraphs give an outline of the steps used to develop the Mechanical Index, its relevance as a potential bioeffects indicator, and some information on other exposure parameters involved in bioeffects research.
mesh_terms: D000162:Acoustics; D000818:Animals; D005740:Gases; D006801:Humans; D011312:Pressure; D014159:Transducers; D014465:Ultrasonics / Q000009:adverse effects
chemical_list: D005740:Gases