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Grueneisen relaxation photoacoustic microscopy
  • Published Date:
    Oct 20 2014
  • Source:
    Phys Rev Lett. 113(17):174301.
Filetype[PDF - 1.23 MB]


Details:
  • Pubmed ID:
    25379919
  • Pubmed Central ID:
    PMC4287460
  • Funding:
    DP1 EB016986/DP/NCCDPHP CDC HHS/United States
    DP1 EB016986/EB/NIBIB NIH HHS/United States
    R01 CA159959/CA/NCI NIH HHS/United States
    R01 CA159959/CA/NCI NIH HHS/United States
    R01 CA186567/CA/NCI NIH HHS/United States
    R01 CA186567/CA/NCI NIH HHS/United States
  • Document Type:
  • Collection(s):
  • Description:
    The temperature-dependent property of the Grueneisen parameter has been employed in photoacoustic imaging mainly to measure tissue temperature. Here we explore this property using a different approach and develop Grueneisen relaxation photoacoustic microscopy (GR-PAM), a technique that images nonradiative absorption with confocal optical resolution. GR-PAM sequentially delivers two identical laser pulses with a microsecond-scale time delay. The first laser pulse generates a photoacoustic signal and thermally tags the in-focus absorbers. When the second laser pulse excites the tagged absorbers within the thermal relaxation time, a photoacoustic signal stronger than the first one is produced, owing to the temperature dependence of the Grueneisen parameter. GR-PAM detects the amplitude difference between the two colocated photoacoustic signals, confocally imaging the nonradiative absorption. We greatly improved axial resolution from 45  μm to 2.3  μm and, at the same time, slightly improved lateral resolution from 0.63  μm to 0.41  μm. In addition, the optical sectioning capability facilitates the measurement of the absolute absorption coefficient without fluence calibration.