Jha Abhinav K, Zhu Yansong, Wong Dean F, Rahmim Arman
Department of Radiology, Johns Hopkins University, Baltimore, MD, USA.
Department of Electrical and Computer Engineering, Baltimore, MD, USA.
Proc SPIE Int Soc Opt Eng. 2017 Feb 11;10137. doi: 10.1117/12.2255802. Epub 2017 Mar 13.
Developing reconstruction methods for diffuse optical imaging requires accurate modeling of photon propagation, including boundary conditions arising due to refractive index mismatch as photons propagate from the tissue to air. For this purpose, we developed an analytical Neumann-series radiative transport equation (RTE)-based approach. Each Neumann series term models different scattering, absorption, and boundary-reflection events. The reflection is modeled using the Fresnel equation. We use this approach to design a gradient-descent-based analytical reconstruction algorithm for a three-dimensional (3D) setup of a diffuse optical imaging (DOI) system. The algorithm was implemented for a three-dimensional DOI system consisting of a laser source, cuboidal scattering medium (refractive index > 1), and a pixelated detector at one cuboid face. In simulation experiments, the refractive index of the scattering medium was varied to test the robustness of the reconstruction algorithm over a wide range of refractive index mismatches. The experiments were repeated over multiple noise realizations. Results showed that by using the proposed algorithm, the photon propagation was modeled more accurately. These results demonstrated the importance of modeling boundary conditions in the photon-propagation model.
开发用于漫射光学成像的重建方法需要对光子传播进行精确建模，包括光子从组织传播到空气时由于折射率不匹配而产生的边界条件。为此，我们开发了一种基于解析诺伊曼级数辐射传输方程（RTE）的方法。每个诺伊曼级数项对不同的散射、吸收和边界反射事件进行建模。反射使用菲涅尔方程进行建模。我们使用这种方法为漫射光学成像（DOI）系统的三维（3D）设置设计一种基于梯度下降的解析重建算法。该算法针对由激光源、长方体散射介质（折射率>1）和位于长方体一个面上的像素化探测器组成的三维DOI系统实现。在模拟实验中，改变散射介质的折射率，以在广泛的折射率不匹配范围内测试重建算法的鲁棒性。实验在多个噪声实现上重复进行。结果表明，通过使用所提出的算法，可以更准确地对光子传播进行建模。这些结果证明了在光子传播模型中对边界条件进行建模的重要性。
