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

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..