Fig. 3. Phantom spectroscopic PA imaging with optical fluence compensation.

GNR (gold nanorods), de-ionized water, and black ink were injected into three different tubes immersed in an absorbing and highly scattering background (1% Intralipid suspension mixed with Prussian blue nanoparticles). a Experimental setup. b First row: B-mode image. Second row: wavelength-compounded, Σλ-PA, image. Third/Fourth row: GNR-weighted PA image without/with optical fluence compensation. The horizontal and vertical axes represent lateral and axial dimensions in units of mm, respectively. Wavelength-dependent fluence was estimated using PA signals at the top of the tube filled with black ink. c The estimated effective optical attenuation coefficient (μ_eff, blue line) is compared to predictions using the UV–VIS measured absorption coefficient of Prussian blue aqueous solution and the reduced scattering coefficient of Intralipid known from the literature⁵⁸ (red shaded region). d Measured spectra (normalized to the area under the spectrum) of GNR (left) and black ink (right) are expressed as mean ± standard deviation. For each panel, the spectrum after fluence compensation (red solid line) is compared to the uncompensated spectrum (blue line) and the reference UV–VIS result (dashed line). e Improvements after fluence compensation for GNR and black ink solutions are quantified in terms of the averaged normalized correlation coefficient (NCC).