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30 May 1995 Photon migration within the P3 approximation
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The diffusion approximation to the photon transport equation is the simplest model for photon migration. The applicability of the diffusion approximation, however, is limited. For example, it is strictly valid only when the absorption coefficient is small compared to the scattering coefficient and the source modulation frequency is small compared to the scattering rate. In this contribution we establish the theoretical range of validity of the diffusion approximation, review a frequency-dependent solution of the transport equation within the P3 approximation, and establish the significance of the P3 solution using Monte Carlo computer simulations. We find that the P3 approximation, in most cases, permits a more accurate determination of the optical properties of highly absorbing media as well as from data obtained at modulation frequencies greater than 3 GHz. Interestingly, for highly anisotropic scattering (g equals 0.9), we find that diffusion theory and the P3 approximation predict approximately the same values for the reduced scattering coefficient.
© (1995) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
David A. Boas, Hanli Liu, Maureen A. O'Leary, Britton Chance, and Arjun G. Yodh "Photon migration within the P3 approximation", Proc. SPIE 2389, Optical Tomography, Photon Migration, and Spectroscopy of Tissue and Model Media: Theory, Human Studies, and Instrumentation, (30 May 1995);

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