title: Quantitative determination of chromophore concentrations from 2D photoacoustic images using a nonlinear model-based inversion scheme.
abstract: A model-based inversion scheme was used to determine absolute chromophore concentrations from multiwavelength photoacoustic images. The inversion scheme incorporated a forward model, which predicted 2D images of the initial pressure distribution as a function of the spatial distribution of the chromophore concentrations. It comprised a multiwavelength diffusion based model of the light transport, a model of acoustic propagation and detection, and an image reconstruction algorithm. The model was inverted by fitting its output to measured photoacoustic images to determine the chromophore concentrations. The scheme was validated using images acquired in a tissue phantom at wavelengths between 590 nm and 980 nm. The phantom comprised a scattering emulsion in which up to four tubes, filled with absorbing solutions of copper and nickel chloride at different concentration ratios, were submerged. Photoacoustic signals were detected along a line perpendicular to the tubes from which images of the initial pressure distribution were reconstructed. By varying the excitation wavelength, sets of multiwavelength photoacoustic images were obtained. The majority of the determined chromophore concentrations were within +/-15% of the true value, while the concentration ratios were determined with an average accuracy of -1.2%.
authors.affiliation: Department of Medical Physics & Bioengineering, University College London, Malet Place Engineering Building, London WC1E 6BT, UK. jlaufer@medphys.ucl.ac.uk
authors.forename: Jan
authors.initials: J
authors.lastname: Laufer
authors.forename: Ben
authors.initials: B
authors.lastname: Cox
authors.forename: Edward
authors.initials: E
authors.lastname: Zhang
authors.forename: Paul
authors.initials: P
authors.lastname: Beard
mesh_terms: D000465:Algorithms; D001704:Biopolymers / Q000032:analysis*; D003198:Computer Simulation; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D033401:Microscopy, Acoustic / Q000379:methods*; D008954:Models, Biological; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D001704:Biopolymers