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Data from: Photoacoustic imaging of rat kidney tissue oxygenation using NIR-II wavelengths

Vincely, Vinoin Devpaul1; Bayer, Carolyn L.1

Published May 03, 2025 on Dryad. https://doi.org/10.5061/dryad.wpzgmsbxn

Data files

May 03, 2025 version files 28.82 MB

Abstract

Significance: Conventionally, spectral photoacoustic imaging (sPAI) to assess tissue oxygenation (sO2) uses optical wavelengths in the first near infrared window (NIR-I). This limits the maximum photoacoustic imaging depth (~1 cm) due to the high spectral coloring of biological tissues and has been a major barrier to the clinical translation of the technique.

Aim: Here, we demonstrate the second near infrared (NIR-II) tissue optical window (950-1400 nm) for the assessment of blood and tissue sO2.

Approach: The NIR-II PA spectra of oxygenated and deoxygenated hemoglobin were first characterized using a phantom. Optimal wavelengths to minimize spectral coloring were identified. The resulting NIR-II PA imaging methods were then validated in vivo by measuring kidney sO2 in adult female rats.

Results: sPAI of whole blood, in a phantom, and of blood in kidneys in vivo, produced PA spectra proportional to wavelength-dependent optical absorption. Using the NIR-II wavelengths for spectral unmixing resulted in a ~50% decrease in the error of the estimated blood sO2, compared to conventional NIR-I wavelengths. In vivo measurements of kidney sO2 validated these findings, with a similar reduction in error when using NIR-II wavelengths versus NIR-I wavelengths.

Conclusions: sPAI using NIR-II wavelengths improved the accuracy of tissue sO2 measurements. This is likely due to reduced scattering, which reduces the attenuation and therefore the impact of spectral coloring in this wavelength range. Combined with the increased safe skin exposure fluence limits in this wavelength range, these results demonstrate the potential to use NIR-II wavelengths for quantitative sPAI of sO2 from deep heterogeneous tissues..