Optical computed tomography in a turbid medium using early arriving photons.
Optical computed tomography in a turbid medium using early arriving photons.
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DOI：
10.1117/1.429981
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发表时间：
2000-04
影响因子：
3.5
通讯作者：
K. Chen;L. Perelman;Q. Zhang;R. Dasari;M. Feld
中科院分区：
文献类型：
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作者：
K. Chen;L. Perelman;Q. Zhang;R. Dasari;M. Feld
我们采用光子迁移图像吸收物体嵌入在混浊介质。为了提高分辨率，我们使用早期到达的光子（比飞行时间多几百皮秒），这是一种扩散近似失效的情况。我们的图像重建方法是基于X射线计算机断层扫描（CT）的光学制度的扩展。CT算法必须推广到考虑光子路径的分布。我们用输运方程的绿色函数表示点扩散函数。然后，该PSF提供用于X射线CT的广义级数展开方法中的加权函数。实验是在散射和吸收特性与人体乳腺组织相似的混浊介质上进行的。将多个吸收剂嵌入培养基中以模拟肿瘤。在两个投影中收集同轴透射扫描，并分析早期部分。通过精确的建模，我们可以消除与多次散射相关的模糊，并获得高分辨率的图像。我们的结果表明，扩散近似PSF是不足以描述早期到达的光子。一个点扩散函数结合因果关系，需要重建混浊介质的准确图像。
We employ photon migration to image absorbing objects embedded in a turbid medium. For improved resolution, we use early arriving photons (a few hundred picoseconds in excess of the time of flight), a regime in which the diffusion approximation breaks down. Our image reconstruction method is based on extension of x-ray computed tomography (CT) to the optical regime. The CT algorithm must be generalized to take into account the distributions of photon paths. We express the point spread function (PSF) in terms of the Green's function for the transport equation. This PSF then provides weighting functions for use in a generalized series expansion method of x-ray CT. Experiments were performed on a turbid medium with scattering and absorption properties similar to those of human breast tissue. Multiple absorbers were embedded into the medium to mimic tumors. Coaxial transmission scans were collected in two projections, and the early-time portions were analyzed. Through accurate modeling, we could remove the blurring associated with multiple scattering and obtain high-resolution images. Our results show that the diffusion approximation PSF is inadequate to describe the early arriving photons. A PSF incorporating causality is required to reconstruct accurate images of turbid media.