Towards Quantitative Evaluation of Tissue Absorption Coefficients Using Light Fluence Correction in Optoacoustic Tomography

Abstract

Optoacoustic tomography is a fast developing imaging modality, combining the high contrast available from optical excitation of tissue with the high resolution and penetration depth of ultrasound detection. Light is subject to both absorption and scattering when traveling through tissue; adequate knowledge of tissue optical properties and hence the spatial fluence distribution is required to create an optoacoustic image that is directly proportional to chromophore concentrations at all depths. Using data from a commercial multispectral optoacoustic tomography (MSOT) system, we implemented an iterative optimization for fluence correction based on a finite-element implementation of the delta-Eddington approximation to the Radiative Transfer Equation (RTE). We demonstrate a linear relationship between the image intensity and absorption coefficients across multiple wavelengths and depths in phantoms. We also demonstrate improved feature visibility and spectral recovery at depth in phantoms and with in vivo measurements, suggesting our approach could in the future enable quantitative extraction of tissue absorption coefficients in biological tissue.

Sulfates as chromophores for multiwavelength photoacoustic imaging phantoms

“…[1][2][3] Since different endogenous, exogenous, and genetically encoded chromophores have different absorption spectra, photoacoustic images obtained at multiple wavelengths carry information on the distributions of these chromophores and, hence, information on tissue composition, physiology, and pathology. 1,2,4,5 Nevertheless, the use of multiwavelength PAI for detecting, isolating, assessing the relative variation, or fully quantifying chromophore contributions in an accurate and robust manner is still challenging 6,7 (a field broadly known as quantitative photoacoustic tomography). Part of the challenge is the access to suitable chromophores and phantoms for proof-of-concept, testing, validation, and optimization.…”

Detection of microspheres in vivo using multispectral optoacoustic tomography

“…Optoacoustic imaging recently has emerged as a viable imaging modality in vivo (Kimbrough et al 2015, Zeiderman et al 2016, Brochu et al 2016, Ermilov et al 2009). Optoacoustic imaging has been used to analyze tissue hypoxia, to identify tumors and to determine biodistribution of nanoparticles at sub-millimeter resolution in murine models (Kimbrough et al 2015, Zeiderman et al 2016, Cao et al 2016, Herzog et al 2012).…”

Fluorescence‐ and multispectral optoacoustic imaging for an optimized detection of deeply located tumors in an orthotopic mouse model of pancreatic carcinoma

“…Nevertheless, similar to fluorescence imaging, MSOT only allows a relative quantification of the signals. In both methods, absolute quantification can only be achieved by a full correction for the absorption, scattering and anisotropy of the tissue, the technology, which is still in its infancy . Other methods such as gamma spectroscopy or mass spectrometry could be considered to be applied in future studies if absolute quantification of signals is needed.…”