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SUMMARY:Photoacoustic Tomography: Ultrasonically Breaking through the Opti
 cal Diffusion Limit - Wang\, LV (Washington University)
DTSTART:20110823T130500Z
DTEND:20110823T135500Z
UID:TALK32463@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:We develop photoacoustic tomography (PAT) for functional and m
 olecular imaging by physically combining optical and ultrasonic waves via 
 energy transduction.  Key applications include early-cancer and functional
  imaging. Light provides rich tissue contrast but does not penetrate biolo
 gical tissue in straight paths as x-rays do.  Consequently\, high-resoluti
 on pure optical imaging (e.g.\, confocal microscopy\, two-photon microscop
 y\, and optical coherence tomography) is limited to depths within one opti
 cal transport mean free path (~1 mm in the skin).  Ultrasonic imaging\, on
  the contrary\, provides good image resolution but suffers from poor contr
 ast in early-stage tumors as well as strong speckle artifacts.  PAT-embodi
 ed in the forms of computed tomography and focused scanning-overcomes the 
 above problems because ultrasonic scattering is ~1000 times weaker than op
 tical scattering. In PAT\, a pulsed laser beam illuminates the tissue and 
 generates a small but rapid temperature rise\, which induces emission of u
 ltrasonic waves due to thermoelastic expansion.  The short-wavelength ultr
 asonic waves are then detected to form high-resolution tomographic images.
  PAT broke through the diffusion limit for penetration and achieved high-r
 esolution images at depths up to 7 cm in tissue. Further depths can be rea
 ched by thermoacoustic tomography (TAT) using microwaves or RF waves inste
 ad of light for excitation.\n
LOCATION:Seminar Room 1\, Newton Institute
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