title: Thermal safety of vibro-acoustography using a confocal transducer.
abstract: Vibro-acoustography (VA) is an imaging method that forms a two-dimensional (2-D) image by moving two cofocused ultrasound beams with slightly different frequencies over the object in a C-scan format and recording acoustic emission from the focal region at the difference frequency. This article studies tissue heating due to a VA scan using a concentric confocal transducer. The three-dimensional (3-D) ultrasound intensity field calculated by Field II is used with the bio-heat equation to estimate tissue heating due to ultrasound absorption. Results calculated with thermal conduction and with blood perfusion, with conduction and without perfusion and without conduction and without perfusion are compared. Maximum heating due to ultrasound absorption occurs in the transducer's near-field and maximum temperature rise in soft tissue during a single VA scan is below 0.05 degrees C for all three attenuation coefficients evaluated: 0.3, 0.5 and 0.7 dB/cm/MHz. Transducer self-heating during a single VA scan measured by a thermocouple is less than 0.27 degrees C.
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN 55905, USA. chen.shigao@mayo.edu
authors.forename: Shigao
authors.initials: S
authors.lastname: Chen
authors.forename: Wilkins
authors.initials: W
authors.lastname: Aquino
authors.forename: Azra
authors.initials: A
authors.lastname: Alizad
authors.forename: Matthew W
authors.initials: MW
authors.lastname: Urban
authors.forename: Randall
authors.initials: R
authors.lastname: Kinnick
authors.forename: James F
authors.initials: JF
authors.lastname: Greenleaf
authors.forename: Mostafa
authors.initials: M
authors.lastname: Fatemi
mesh_terms: D054459:Elasticity Imaging Techniques / Q000379:methods*; D006801:Humans; D012449:Safety; D013817:Thermography; D014159:Transducers; D014465:Ultrasonics