Yang Defu, Chen Xueli, Cao Xu, Wang Jing, Liang Jimin, Tian Jie
Engineering Research Center of Molecular and Neuro Imaging of Ministry of Education, School of Life Science and Technology, Xidian University, Xi'an, 710071, Shaanxi, China.
Department of Nuclear Medicine, Xijing Hospital, Fourth Military Medical University, Xi'an, 710032, Shaanxi, China.
Med Biol Eng Comput. 2015 Sep;53(9):805-14. doi: 10.1007/s11517-015-1293-8. Epub 2015 Apr 8.
The third-order simplified harmonic spherical approximation (SP3) and diffusion approximation (DA) equations have been widely used in the three-dimensional (3D) whole-body optical imaging of small animals. With different types of tissues, which were classified by the ratio of µ s'/µ ɑ, the two equations have their own application scopes. However, the classification criterion was blurring and unreasonable, and the scope has not been systematically investigated until now. In this study, a new criterion for classifying tissues was established based on the absolute value of absorption and reduced scattering coefficients. Using the newly defined classification criterion, the performance and applicability of the SP3 and DA equations were evaluated with a series of investigation experiments. Extensive investigation results showed that the SP3 equation exhibited a better performance and wider applicability than the DA one in most of the observed cases, especially in tissues of low-scattering-low-absorption and low-scattering-high-absorption range. For the case of tissues with the high-scattering-low-absorption properties, a similar performance was observed for both the SP3 and the DA equations, in which case the DA was the preferred option for 3D whole-body optical imaging. Results of this study would provide significant reference for the study of hybrid light transport models.
三阶简化谐波球近似（SP3）方程和扩散近似（DA）方程已广泛应用于小动物的三维（3D）全身光学成像。对于按µs'/µɑ比值分类的不同类型组织，这两个方程有各自的应用范围。然而，该分类标准模糊且不合理，且其范围至今尚未得到系统研究。在本研究中，基于吸收系数和约化散射系数的绝对值建立了一种新的组织分类标准。利用新定义的分类标准，通过一系列研究实验对SP3方程和DA方程的性能及适用性进行了评估。大量研究结果表明，在大多数观察到的情况下，SP3方程比DA方程表现出更好的性能和更广泛的适用性，特别是在低散射低吸收和低散射高吸收范围内的组织中。对于具有高散射低吸收特性的组织，SP3方程和DA方程表现出相似的性能，在这种情况下，DA是3D全身光学成像的首选选项。本研究结果将为混合光传输模型的研究提供重要参考。
