Paulsen K D, Jiang H
Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755, USA.
Med Phys. 1995 Jun;22(6):691-701. doi: 10.1118/1.597488.
A finite element reconstruction algorithm for optical data based on a diffusion equation approximation is presented. A frequency domain approach is adopted and a unified formulation for three combinations of boundary observables and conditions is described. A multidetector, multisource measurement and excitation strategy is simulated, which includes a distributed model of the light source that illustrates the flexibility of the methodology to modeling adaptations. Simultaneous reconstruction of both absorption and scattering coefficients for a tissue-like medium is achieved for all three boundary data types. The algorithm is found to be computationally practical, and can be implemented without major difficulties in a workstation computing environment. Results using simulated data suggest that qualitative images can be produced that readily highlight the location of absorption and scattering heterogeneities within a circular background region of close to 4 cm in diameter over a range of contrast levels. Absorption images appear to more closely identify the true size of the heterogeneity; however, both the absorption and scattering reconstructions have difficulty with sharp transitions at increasing depth. Quantitatively, the reconstructions are not accurate, suggesting that absolute optical imaging involving simultaneous recovery of both absorption and scattering profiles in multicentimeter tissues geometries may prove to be extremely difficult.
提出了一种基于扩散方程近似的光学数据有限元重建算法。采用频域方法，并描述了边界可观测量和条件的三种组合的统一公式。模拟了多探测器、多源测量和激发策略，其中包括光源的分布式模型，该模型说明了该方法在建模适应性方面的灵活性。对于所有三种边界数据类型，都实现了对类组织介质的吸收系数和散射系数的同时重建。该算法在计算上是可行的，并且在工作站计算环境中可以没有重大困难地实现。使用模拟数据的结果表明，可以生成定性图像，这些图像能够在一系列对比度水平下，轻松突出直径接近4厘米的圆形背景区域内吸收和散射不均匀性的位置。吸收图像似乎能更准确地识别不均匀性的真实大小；然而，吸收和散射重建在深度增加时的急剧转变方面都存在困难。从定量角度来看，重建并不准确，这表明在多厘米组织几何结构中同时恢复吸收和散射剖面的绝对光学成像可能极其困难。
