Zhou Xiaodong, Zhu Timothy C, Finlay Jarod C, Li Jun, Dimofte Andreea, Hahn Steve
Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA 19104.
Proc SPIE Int Soc Opt Eng. 2007 Jan 20;6434. doi: 10.1117/12.701717.
We have developed an efficient Levenberg-Marquardt iterative algorithm utilizing a three-dimensional field measurements coupled to a two-dimensional optical property reconstruction scheme. This technique takes advantage of accurate estimation of light distribution in 3D forward calculation and reduced problem size and less computation time in 2D inversion. Important advances in terms of improving algorithm efficiency and accuracy include use of an iterative general minimum residual method (GMRES) for computing the field solutions, application of the dual mesh scheme and adjoint method for Jacobian construction, and implementation of normalization scheme to reduce the absorption-scattering cross talk. The synthetic measurement data were calculated for a cubic phantom containing a single absorption anomaly and a single scattering anomaly. The model had a background of μ=0.03mm and μ'=1.4mm. The absorption and scattering anomalies have the μ = 0.06 mm and μ' = 2.0 mm. Five sources and 72 detectors are used per slice. A typical human prostate is composed of 6 slices. The reconstruction images successfully recover the both anomalies with good localization. Experiment data from tissue simulated phantom are also presented. The clinical DOT imaging was performed before photodynamic therapy based on the protocol. The preliminary results showed the reconstructed prostate μa varied between 0.025 and 0.07 mm and μ' ranged from 1.1 to 2 mm. These results show that this new 2D-3D hybrid algorithm consistently outperform the 2D-2D or 3D-3D counterparts.
我们开发了一种高效的Levenberg-Marquardt迭代算法,该算法利用三维场测量与二维光学特性重建方案相结合。该技术利用了三维正向计算中光分布的精确估计,以及二维反演中问题规模的减小和计算时间的减少。在提高算法效率和准确性方面的重要进展包括使用迭代广义最小残差法(GMRES)来计算场解,应用对偶网格方案和伴随方法来构建雅可比矩阵,以及实施归一化方案以减少吸收-散射串扰。针对包含单个吸收异常和单个散射异常的立方模型计算了合成测量数据。该模型的背景为μ=0.03mm和μ'=1.4mm。吸收和散射异常分别为μ = 0.06 mm和μ' = 2.0 mm。每一层使用五个光源和72个探测器。一个典型的人类前列腺由6层组成。重建图像成功地恢复了两个异常,定位良好。还展示了来自组织模拟模型的实验数据。基于该方案在光动力治疗前进行了临床漫反射光学断层成像。初步结果显示,重建的前列腺μa在0.025至0.07 mm之间变化,μ'在1.1至2 mm之间。这些结果表明,这种新的二维-三维混合算法始终优于二维-二维或三维-三维对应算法。