Arterial Blood-Mediated Deep-Tissue Photoacoustic Oximetry

Area of Science:

• Biomedical Optics
• Medical Imaging
• Biophysics

Background:

• Photoacoustic tomography offers high-resolution deep-tissue blood-oxygenation (sO2) imaging.
• Spectral coloring, caused by wavelength-dependent optical fluence changes, hinders accurate photoacoustic oximetry.
• Existing methods struggle with reliable sO2 estimation in deep tissues.

Purpose of the Study:

• To introduce and validate the arterial prior method (APM+) for accurate deep-tissue photoacoustic oximetry.
• To overcome the challenge of spectral coloring in photoacoustic imaging.
• To improve the reliability and accuracy of blood-oxygenation measurements in vivo.

Main Methods:

• Developed the arterial prior method (APM+), incorporating intravascular fluence correction.
• Utilized the high arterial sO2 to locally calibrate optical fluence, mitigating spectral coloring effects.
• Validated APM+ in phantom experiments with ex vivo animal tissue and human imaging studies.

Main Results:

• APM+ achieved a median estimation error of 2.9% in phantom studies, significantly outperforming the traditional linear unmixing method (LUM) at 9.8%.
• Human imaging of radial artery-vein pairs showed APM+ yielded venous sO2 estimates (median: 72.3%, IQR: 8.9%) within the healthy range, unlike LUM (median: 75.2%, IQR: 34.4%).
• APM+ demonstrated robust and consistent sO2 estimates with increasing tissue depth (up to 1.5 cm).

Conclusions:

• The arterial prior method (APM+) effectively corrects for spectral coloring in photoacoustic imaging.
• APM+ provides more accurate and reliable deep-tissue blood-oxygenation (sO2) measurements compared to conventional methods.
• This advancement holds promise for improved clinical diagnostics and research utilizing photoacoustic oximetry.