Fluence compensation in raster-scan optoacoustic angiography

Abstract

Modern optical imaging techniques demonstrate significant potential for high resolution in vivo angiography. Optoacoustic angiography benefits from higher imaging depth as compared to pure optical modalities. However, strong attenuation of optoacoustic signal with depth provides serious challenges for adequate 3D vessel net mapping, and proper compensation for fluence distribution within biotissues is required. We report on the novel approach allowing to estimate effective in-depth fluence profiles for optoacoustic systems. Calculations are based on Monte Carlo simulation of light transport and account for complex illumination geometry and acoustic detection parameters. The developed fluence compensation algorithm was tested in in vivo angiography of human palm and allowed to overcome significant in-depth attenuation of probing radiation and enhance the contrast of lower dermis plexus while preserving high resolution of upper plexus imaging.

Uniform light delivery in volumetric optoacoustic tomography

“…When the sphere was uniformly illuminated, its entire surface became visible with the reconstructed images, accurately resembling the theoretically predicted (simulated) values. Even though it has been shown that OA images can, in principle, be corrected for nonuniform illumination and light attenuation, it was not necessary in this case . Such correction for limited‐view conditions or for a relatively low number of measuring positions can be still hampered by streak‐type artifacts associated with strong nonuniformity of the excitation light field (hot spots) .…”

Real-time spectroscopic photoacoustic/ultrasound (PAUS) scanning with simultaneous fluence compensation and motion correction for quantitative molecular imaging

“…Fortunately, the current fast-sweep PAUS system can be programmed to interleave US images at frame rates greater than the 50 Hz PA frame rate. ) [34][35][36][37][38][39][40][41][42][43]. They can be estimated ex vivo or even in vivo but require additional equipment and significant measurement time not compatible with real-time imaging [33,34,40,43,70].…”

“…Unfortunately, this requires a precise map of tissue optical properties, which cannot be measured or calculated during imaging. Several methods have attempted to estimate and compensate fluence variations [34][35][36][37][38][39][40][41][42][43], but none work well clinically where real-time or near real-time corrections are needed. In most cases, fluence is compensated using an approximate exponential function equalizing intensities.…”

Combination of virtual point detector concept and fluence compensation in acoustic resolution photoacoustic microscopy

“…14 In this paper, we report a reconstruction algorithm comprising improved SAFT algorithm 1,11,15,16 accounting for both the spatial response 17 of the acoustic antenna 10 and the spatial distribution of optical fluence. 14,18 For precise calculation of rapid in-depth attenuation of probing laser radiation, we employ 3-D Monte Carlo code previously customized for simulation of the complex geometry of AR-PAM light illumination in medium with optical properties typical for biotissues. 14 At the first step, the SAFT procedure with account for antenna spatial response (ASR) is performed.…”

“…14,18 For precise calculation of rapid in-depth attenuation of probing laser radiation, we employ 3-D Monte Carlo code previously customized for simulation of the complex geometry of AR-PAM light illumination in medium with optical properties typical for biotissues. 14 At the first step, the SAFT procedure with account for antenna spatial response (ASR) is performed. Accurate account for the ASR is considered along with the proposed simplified approach allowing for significant speedup in processing.…”