Two schemes for quantitative photoacoustic tomography based on Monte Carlo simulation

Area of Science:

• Biomedical Optics
• Medical Imaging
• Computational Modeling

Background:

• Accurate determination of optical absorption coefficients in biological tissues is crucial for various medical imaging and diagnostic applications.
• Conventional quantitative photoacoustic tomography (PAT) methods often rely on diffusion approximation, which can be inaccurate in highly scattering or absorbing tissues.
• Monte Carlo (MC) simulation offers a more accurate way to model photon transport but is computationally intensive and not easily integrated into standard PAT reconstruction.

Purpose of the Study:

• To develop and validate novel quantitative photoacoustic tomography (PAT) methods for determining the optical absorption coefficient of biological tissues.
• To integrate Monte Carlo (MC) simulation with conventional PAT reconstruction to improve accuracy, especially in challenging optical conditions.
• To address the limitations of diffusion approximation in quantitative PAT by employing more robust photon transport modeling.

Main Methods:

• Proposed two quantitative photoacoustic tomography (PAT) methods that combine conventional PAT with Monte Carlo (MC) simulation.
• The methods were theoretically and experimentally validated using simulations, tissue-mimicking phantoms, ex vivo, and in vivo tests.
• Investigated performance with objects of varying absorption contrasts and in high-absorption media where diffusion approximation fails.

Main Results:

• Reconstructions demonstrated quantitative accuracy in target location, size, and optical properties.
• Off-center error for circular targets was less than 0.1 mm.
• Errors in reconstructed sizes ranged from 0% to 26%, and errors in optical properties ranged from 0% to 12.5%.

Conclusions:

• The developed methods can quantitatively reconstruct absorbing objects of diverse sizes and optical contrasts.
• These techniques are effective even when the diffusion approximation fails to accurately describe photon propagation in biological tissues.
• The study successfully resolved intrinsic difficulties in quantitative PAT associated with combining conventional PAT with diffusion approximation or radiation transport modeling.