Effects of the approximations of light propagation on quantitative photoacoustic tomography using two-dimensional photon diffusion equation and linearization
Effects of the approximations of light propagation on quantitative photoacoustic tomography using two-dimensional photon diffusion equation and linearization
复制标题
使用二维光子扩散方程和线性化的光传播近似对定量光声层析成像的影响
DOI：
10.1007/s10043-017-0369-0
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发表时间：
2017
期刊：
影响因子：
1.2
通讯作者：
Shinpei Okawa,Takeshi Hirasawa,Toshihiro Kushibiki,Miya Ishihara
中科院分区：
文献类型：
--
作者：
H. Iyota;T. Inoue;J. Yamagata;Shinpei Okawa,Takeshi Hirasawa,Toshihiro Kushibiki,Miya Ishihara
采用光传播模型的定量光声断层扫描（QPAT）将通过量化血红蛋白或造影剂的浓度在医学诊断中发挥重要作用。然而，采用三维（3D）辐射传递方程（RTE）的光传播模型进行的QPAT在重建吸收系数的更新过程中涉及的迭代正向计算中需要巨大的计算量。光传播的近似提高了 QPAT 图像重建的效率。在本研究中，我们将近似 3D RTE 的 3D/二维 (2D) 光子扩散方程 (PDE) 与基于 3D RTE 的蒙特卡罗模拟进行了比较。然后，在数值模拟中定量论证和讨论了基于二维偏微分方程的线性图像重建中由近似引起的误差。可以清楚地观察到近似值影响重建的吸收系数。基于2D PDE的线性化算法成功地对3D体模中吸收系数较大的区域进行了图像重建。体模实验中的重建值与数值模拟中的重建值一致，从而验证了图像重建的数值模拟利用基于2D PDE的线性化算法预测了3D介质中目标的真实吸收系数与重建值之间的关系。此外，在数值模拟预测的基础上，根据 2D 重建图像估计了 3D 介质中的真实吸收系数。尽管暴露出一些局限性，但模型实验中的估计是成功的。
Quantitative photoacoustic tomography (QPAT) employing a light propagation model will play an important role in medical diagnoses by quantifying the concentration of hemoglobin or a contrast agent. However, QPAT by the light propagation model with the three-dimensional (3D) radiative transfer equation (RTE) requires a huge computational load in the iterative forward calculations involved in the updating process to reconstruct the absorption coefficient. The approximations of the light propagation improve the efficiency of the image reconstruction for the QPAT. In this study, we compared the 3D/two-dimensional (2D) photon diffusion equation (PDE) approximating 3D RTE with the Monte Carlo simulation based on 3D RTE. Then, the errors in a 2D PDE-based linearized image reconstruction caused by the approximations were quantitatively demonstrated and discussed in the numerical simulations. It was clearly observed that the approximations affected the reconstructed absorption coefficient. The 2D PDE-based linearized algorithm succeeded in the image reconstruction of the region with a large absorption coefficient in the 3D phantom. The value reconstructed in the phantom experiment agreed with that in the numerical simulation, so that it was validated that the numerical simulation of the image reconstruction predicted the relationship between the true absorption coefficient of the target in the 3D medium and the reconstructed value with the 2D PDE-based linearized algorithm. Moreover, the the true absorption coefficient in 3D medium was estimated from the 2D reconstructed image on the basis of the prediction by the numerical simulation. The estimation was successful in the phantom experiment, although some limitations were revealed.