Experimental Study on CW Diffuse Reflective Optical CT

该项目是一个可行性研究的扩散光学断层扫描，具有3-D空间分辨率，使用2维连续波源探测器阵列在身体表面上，旨在真实的时间成像的大脑激活最小的皮肤循环波动的污染。我们制定了基于Rytov近似的光子迁移的扩散方程近似的吸收系数的小扰动的正问题，并制定了三维层析重建使用简单的正则化的Moore-Penrose伪逆。我们分析了重建误差和空间分辨率对正则化参数、目标深度和重建体素大小的依赖关系。研究表明，重建误差和空间分辨率之间的权衡不依赖于体素的大小。然而，发现简单的正则化逆具有重建灵敏度的强深度依赖性，使得 ...更多信息 深度中的目标脑信号将容易被浅范围中的不想要的皮肤循环信号掩盖。我们设计了深度自适应体素大小的方法和深度自适应正则化，这两个被证明是有效的，以克服这个严重的问题。基于这些广泛的模拟研究，我们澄清了空间分辨率，重建噪声，重建感兴趣的区域和重建灵敏度的均匀性等之间的权衡。为了评估实验的可行性，我们修改了现有的商业光学地形图，使数字数据采集重建，并检查性能的幻影研究。最后，利用现有地形仪的源-探测器系统设计了一个实用的成像系统。该系统将在距皮肤表面1cm深度处假设的大脑皮层的4cm X 4cm区域中以1cm的空间分辨率可视化大脑活动，其中抑制了20 dB的不需要的皮肤循环信号。少

This project is a feasibility study on diffuse optical tomography which has 3-D spatial resolution using 2-dimensional CW source-detector arrays on the body surface, aiming at real time imaging of the brain activation minimally contaminated by skin circulation fluctuation. We formulated the forward problem based on the Rytov approximation for the small perturbation of the absorption coefficients in the diffusion equation approximation of the photon migration, and formulated the 3-D tomographic reconstruction using simple regularized Moore-Penrose pseudo inverse. We analyzed the dependencies of the reconstruction error and the spatial resolution on the regularization parameter, the target depth and the reconstruction voxel size. The study showed that the trade-off between the reconstruction error and the spatial resolution does not depend on the voxel size. The simple regularized inverse, however, was found to have strong depth dependencies of the reconstruction sensitivity so that the … More target brain signal in the depth would be easily masked by the unwanted skin circulation signal in the shallow range. We devised the depth-adaptive voxel size method and the depth-adaptive regularization, both of which were shown to be effective to overcome this serious problem. Based on these extensive simulation studies, we clarified trade-offs between spatial resolution, reconstruction noise, reconstruction region of interest and the uniformity of the reconstruction sensitivity etc. To assess the feasibility experimentally, we modified a existing commercial optical topograph, enabling digital data acquisition for the reconstruction, and checked the performance by phantom study. Finally, we designed a practical imaging system with the source-detector system of the existing topograph. The system would visualize the brain activity with the spatial resolution of 1cm in the 4cm X 4cm area of the cerebral cortex assumed at the 1cm depth from the skin surface with the 20 dB suppression of the unwanted skin circulation signal. Less