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首页> 外文会议>Photons Plus Ultrasound: Imaging and Sensing 2006; Progress in Biomedical Optics and Imaging; vol.7, no.9 >Modeling of photon migration in the human lung using a finite volume solver
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Modeling of photon migration in the human lung using a finite volume solver

机译：使用有限体积求解器模拟人肺中的光子迁移

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The application of the frequency domain and steady-state diffusive optical spectroscopy (DOS) and steady-state near infrared spectroscopy (NIRS) to diagnosis of the human lung injury challenges many elements of these techniques. These include the DOS/MRS instrument performance and accurate models of light transport in heterogeneous thorax tissue. The thorax tissue not only consists of different media (e.g. chest wall with ribs, lungs) but its optical properties also vary with time due to respiration and changes in thorax geometry with contusion (e.g. pneumothorax or hemothorax). This paper presents a finite volume solver developed to model photon migration in the diffusion approximation in heterogeneous complex 3D tissues. The code applies boundary conditions that account for Fresnel reflections. We propose an effective diffusion coefficient for the void volumes (pneumothorax) based on the assumption of the Lambertian diffusion of photons entering the pleural cavity and accounting for the local pleural cavity thickness. The code has been validated using the MCML Monte Carlo code as a benchmark. The code environment enables a semi-automatic preparation of 3D computational geometry from medical images and its rapid automatic meshing. We present the application of the code to analysis/optimization of the hybrid DOS/NIRS/ultrasound technique in which ultrasound provides data on the localization of thorax tissue boundaries. The code effectiveness (3D complex case computation takes 1 second) enables its use to quantitatively relate detected light signal to absorption and reduced scattering coefficients that are indicators of the pulmonary physiologic state (hemoglobin concentration and oxygenation).
机译：频域和稳态扩散光谱（DOS）以及稳态近红外光谱（NIRS）在诊断人肺损伤中的应用对这些技术的许多要素提出了挑战。其中包括DOS / MRS仪器的性能以及异种胸腔组织中光传输的精确模型。胸腔组织不仅由不同的介质组成（例如带有肋骨的胸壁，肺部），而且由于呼吸作用以及随挫伤的胸腔几何形状的变化（例如气胸或血胸），其光学特性也会随时间而变化。本文提出了一种有限体积求解器，用于求解异质复杂3D组织中扩散近似中的光子迁移。该代码应用了考虑菲涅耳反射的边界条件。我们基于进入胸膜腔的光子的朗伯扩散并考虑局部胸膜腔厚度的假设，为空隙体积（气胸）提出了有效的扩散系数。该代码已使用MCML蒙特卡洛代码作为基准进行了验证。代码环境可以从医学图像及其快速的自动网格划分中自动准备3D计算几何。我们介绍了该代码在混合/ DOS / NIRS /超声技术的分析/优化中的应用，在超声/超声技术中超声提供了关于胸组织边界定位的数据。代码有效性（3D复杂案例计算需要1秒钟）使其能够将检测到的光信号与吸收和降低的散射系数定量相关，这些吸收系数和降低的散射系数是肺部生理状态（血红蛋白浓度和氧合作用）的指标。

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