Pei Y, Graber H L, Barbour R L
Appl Opt. 2001 Nov 1;40(31):5755-69. doi: 10.1364/ao.40.005755.
Optical measurements of tissue can be performed in discrete, time-averaged, and time-varying data collection modes. This information can be evaluated to yield estimates of either absolute optical coefficient values or some relative change in these values compared with a defined state. In the case of time-varying data, additional analysis can be applied to define various dynamic features. Here we have explored the accuracy with which such information can be recovered from dense scattering media using linear perturbation theory, as a function of the accuracy of the reference medium that serves as the initial guess. Within the framework of diffusion theory and a first-order solution, we have observed the following inequality regarding the sensitivity of computed measures to inaccuracy in the reference medium: Absolute measures ? relative measures > dynamic measures. In fact, the fidelity of derived dynamic measures was striking; we observed that accurate measures of dynamic behavior could be defined even if the quality of the image data from which these measures were derived was comparatively modest. In other studies we identified inaccuracy in the estimates of the reference detector values, and not to corresponding errors in the image operators, as the primary factor responsible for instability of absolute measures. The significance of these findings for practical imaging studies of tissue is discussed.
组织的光学测量可以在离散、时间平均和随时间变化的数据采集模式下进行。这些信息可以进行评估，以得出绝对光学系数值的估计值，或者与定义状态相比这些值的一些相对变化。对于随时间变化的数据，可以应用额外的分析来定义各种动态特征。在这里，我们利用线性微扰理论，探讨了从密集散射介质中恢复此类信息的准确性，它是作为初始猜测的参考介质准确性的函数。在扩散理论和一阶解的框架内，我们观察到关于计算测量对参考介质不准确的敏感性的以下不等式：绝对测量值＞相对测量值＞动态测量值。事实上，导出的动态测量值的保真度非常显著；我们观察到，即使从中导出这些测量值的图像数据质量相对一般，也可以定义动态行为的准确测量值。在其他研究中，我们发现参考探测器值估计中的不准确，而非图像算子中的相应误差，是导致绝对测量值不稳定的主要因素。本文讨论了这些发现对组织实际成像研究的意义。
