title: Photoacoustic ultrasound.
abstract: Differential absorption has been detected and localized in three-dimensions by recording the photoacoustic pulses that were produced when short-duration (approximately 1 microsecond) pulses of electromagnetic energy were absorbed regionally within a turbid medium. These absorption sites were localized with a spatial resolution of approximately 6 mm within a 20 x 20 x 7.5-cm3 volume of 0.3% Liposyn solution, a highly scattering medium. A Xenon flashlamp, delivering a nominal 1 microsecond pulse of broadband light, was used to irradiate the Liposyn solution. Photoacoustic echoes were recorded with a focused, ultrasonic transducer, tuned to a nominal frequency of 0.5 MHz. The spatial resolution that was demonstrated is consistent with the expected ultrasonic properties of the transducer. Improved spatial resolution can be expected with shorter-duration radiation exposure and higher-frequency transducer designs. The technique is generalizable to any electromagnetic energy range (including long-wavelength microwaves) that penetrates the medium and produces differential, regional absorption of energy.
authors.affiliation: Radiology Department, Indiana University Medical Center, Indianapolis 46202-5111.
authors.forename: R A
authors.initials: RA
authors.lastname: Kruger
mesh_terms: D000162:Acoustics / Q000295:instrumentation*; D055592:Biophysical Phenomena; D001703:Biophysics; D055590:Electromagnetic Phenomena; D006801:Humans; D008027:Light; D008961:Models, Structural; D008962:Models, Theoretical; D055095:Optics and Photonics / Q000295:instrumentation*; D012542:Scattering, Radiation; D014465:Ultrasonics