快速估计荧光分子断层成像中单个荧光物的深度

Rapid Estimate of the Depth of Single Point Fluorescence Source for Fluorescence Molecular Tomography

荧光分子断层成像支持在体无创研究长时间跨度的分子事件,满足21世纪系统化地观测生命过程的要求。在其复杂且耗时的重建中,先验信息有助于加快重建速度,提高重建图像的质量。文章将求解荧光物的深度作为待优化问题,由单幅荧光图像直接快速地估计深度信息。首先根据生物组织内的扩散模型和外推边界条件,推导出生物体边界上两点处荧光强度的比值Rf。然后用粒子群优化算法,在吸收系数和散射系数的估计区间内,由最小化生物体边界上两点处模型值RfM与测量值RfT之间的差,估计出荧光物的深度。不同尺寸荧光物的两个仿体实验的结果表明,所提出的方法不需要网格剖分和重建,能快速简单地估计出单个类似于球体的荧光物的深度。

Fluorescence molecular tomography （FMT） supports monitoring molecular events non-invasively in vivo over a span of long time,and meets the demands of monitoring a process of life.Priori information can be applied to speed the complex and time-consuming reconstruction process and to enhance the quality of the reconstructed images for FMT.A method was proposed in the present paper to estimate rapidly the depth of fluorescence source.The estimation process was accomplished with an optimization algorithm,particle swarm optimization （PSO）.Firstly the fluorescence intensity ratio Rf of two positions on the boundary of tissue was derived under extrapolated boundary condition and a diffusion model for the propagation of near-infrared photons in biological tissue.Then a PSO algorithm was applied to minimize the difference between the theoretical ratio RTf and the measured ratio RMf.The depth of fluorescence source was estimated after the rapid PSO optimization process.Two phantoms indicated that the proposed method can estimate the depth of single fluorescence source rapidly and easily without the time-consuming mesh generation and reconstruction process.