In Vitro and In Vivo Multispectral Photoacoustic Imaging for the Evaluation of Chromophore Concentration

Abstract

Multispectral photoacoustic imaging is a powerful noninvasive medical imaging technique that provides access to functional information. In this study, a set of methods is proposed and validated, with experimental multispectral photoacoustic images used to estimate the concentration of chromophores. The unmixing techniques used in this paper consist of two steps: (1) automatic extraction of the reference spectrum of each pure chromophore; and (2) abundance calculation of each pure chromophore from the estimated reference spectra. The compared strategies bring positivity and sum-to-one constraints, from the hyperspectral remote sensing field to multispectral photoacoustic, to evaluate chromophore concentration. Particularly, the study extracts the endmembers and compares the algorithms from the hyperspectral remote sensing domain and a dedicated algorithm for segmentation of multispectral photoacoustic data to this end. First, these strategies are tested with dilution and mixing of chromophores on colored 4% agar phantom data. Then, some preliminary in vivo experiments are performed. These consist of estimations of the oxygen saturation rate (sO2) in mouse tumors. This article proposes then a proof-of-concept of the interest to bring hyperspectral remote sensing algorithms to multispectral photoacoustic imaging for the estimation of chromophore concentration.

Visualizing the early-stage testicular torsion by dual-modal photoacoustic and ultrasound imaging

“…S3 ). In particular, dual-wavelength (750/850 nm) PAI was carried out, which was able to quantify sO 2 of biological tissues based on the distinct molar extinction coefficients of HbR and HbO 2 [25] , [26] , [27] . In addition, USI allowed parallel data collection of color pixel density (CPD) with color Doppler mode and concurrent peak systolic velocity (PSV) or resistance index (RI) imaging by spectral Doppler mode.…”

Evaluation of multispectral unmixing algorithm for HbO2 and HbR

“…The SVD decomposition of matrix M is given by M = UΣV T . The principal components (PCs), represented by the columns of the matrix V is obtained through SVD decomposition of M, can be projected onto the PC directions as follows [23]:…”

Organ‐PAM: Photoacoustic Microscopy of Whole‐organ Multiset Vessel Systems

“…This angiography is developed based on a fundamental photoacoustic phenomenon, which presents the amplitude of a photoacoustic wave linearly proportional to the concentration of the chromophore inside the absorber. [18,19] According to the photoacoustic effect, samples labeled with different concentrations of chromophore can be distinguished by linear mapping between chromophore concentration and photoacoustic amplitude. We prepared soybean oil-based solutions dissolved with oil-soluble ink as a chromophore featuring a flat optical absorption spectrum, and then tested the solutions with varying ink concentrations in a multiset vessel phantom using a five-channel microfluidic chip (Figure 2a,b).…”