University of Illinois Urbana-Champaign, Department of Bioengineering, Urbana, Illinois, United States.
Washington University in St. Louis, Department of Electrical and Systems Engineering, St. Louis, Mis, United States.
J Biomed Opt. 2022 Mar;27(3). doi: 10.1117/1.JBO.27.3.036001.
In three-dimensional (3D) functional optoacoustic tomography (OAT), wavelength-dependent optical attenuation and nonuniform incident optical fluence limit imaging depth and field of view and can hinder accurate estimation of functional quantities, such as the vascular blood oxygenation. These limitations hinder OAT of large objects, such as a human female breast.
We aim to develop a measurement-data-driven method for normalization of the optical fluence distribution and to investigate blood vasculature detectability and accuracy for estimating vascular blood oxygenation.
The proposed method is based on reasonable assumptions regarding breast anatomy and optical properties. The nonuniform incident optical fluence is estimated based on the illumination geometry in the OAT system, and the depth-dependent optical attenuation is approximated using Beer-Lambert law.
Numerical studies demonstrated that the proposed method significantly enhanced blood vessel detectability and improved estimation accuracy of the vascular blood oxygenation from multiwavelength OAT measurements, compared with direct application of spectral linear unmixing without optical fluence compensation. Experimental results showed that the proposed method revealed previously invisible structures in regions deeper than 15 mm and/or near the chest wall.
The proposed method provides a straightforward and computationally inexpensive approximation of wavelength-dependent effective optical attenuation and, thus, enables mitigation of the spectral coloring effect in functional 3D OAT imaging.
在三维（3D）功能光声断层扫描（OAT）中，波长相关的光衰减和不均匀的入射光通量限制了成像深度和视场，并且可能阻碍对功能量的准确估计，例如血管血氧饱和度。这些限制阻碍了大型物体（例如女性乳房）的 OAT。
我们旨在开发一种用于归一化光通量分布的测量数据驱动方法，并研究用于估计血管血氧饱和度的血流检测能力和准确性。
所提出的方法基于对乳房解剖结构和光学特性的合理假设。根据 OAT 系统中的照明几何形状估计不均匀入射光通量，并使用 Beer-Lambert 定律近似深度相关的光衰减。
数值研究表明，与不进行光通量补偿的直接光谱线性解混相比，该方法显著提高了血管检测能力，并提高了多波长 OAT 测量中血管血氧饱和度的估计准确性。实验结果表明，该方法揭示了以前在 15mm 以上深度或靠近胸壁的区域中不可见的结构。
该方法提供了一种简单且计算成本低廉的波长相关有效光衰减的近似值，从而能够减轻功能 3D OAT 成像中的光谱颜色效应。
