title: Should the mechanical index be revised for ARFI imaging?
abstract: The mechanical index (MI) quantifies the likelihood that exposure to diagnostic ultrasound will produce an adverse biological effect by a nonthermal mechanism. The current formulation of the MI is based on inertial cavitation thresholds in two liquids, water and blood, as calculated by a formalism assuming very short pulse durations. Although tissue contains a high proportion of water, it is not a liquid but a viscoelastic solid. Further, acoustic radiation force impulse imaging employs high-intensity pulses up to several hundred acoustic periods long. The effect of these differences was studied in water, blood and five representative tissues.
authors.affiliation: National Center for Physical Acoustics and Department of Physics, The University of Mississippi University, MS 38677.
authors.forename: Charles C
authors.initials: CC
authors.lastname: Church
authors.affiliation: National Center for Physical Acoustics and Department of Physics, The University of Mississippi University, MS 38677.
authors.forename: Cecille
authors.initials: C
authors.lastname: Labuda
authors.affiliation: Department of Biomedical Engineering, Duke University, Durham, NC 27708.
authors.forename: Kathryn
authors.initials: K
authors.lastname: Nightingale
keywords: ARFI; Acoustic Radiation Force Imaging; MI; bioeffects; inertial cavitation; mechanical index