Paithankar D Y, Chen A U, Pogue B W, Patterson M S, Sevick-Muraca E M
Appl Opt. 1997 Apr 1;36(10):2260-72. doi: 10.1364/ao.36.002260.
The feasibility of employing fluorescent contrast agents to perform optical imaging in tissues and other scattering media has been examined through computational studies. Fluorescence lifetime and yield can give crucial information about local metabolite concentrations or environmental conditions within tissues. This information can be employed toward disease detection, diagnosis, and treatment if noninvasively quantitated from reemitted optical signals. However, the problem of inverse image reconstruction of fluorescence yield and lifetime is complicated because of the highly scattering nature of the tissue. Here a light propagation model employing the diffusion equation is used to account for the scattering of both the excitation and fluorescent light. Simulated measurements of frequency-domain parameters of fluorescent modulated ac amplitude and phase lag are used as inputs to an inverse image-reconstruction algorithm, which employs the diffusion model to predict frequency-domain measurements resulting from a modulated input at the phantom periphery. In the inverse image-reconstruction algorithm, a Newton-Raphson technique combined with a Marquardt algorithm is employed to converge on the fluorescent properties within the medium. The successful reconstruction of both the fluorescence yield and lifetime in the case of a heterogeneous fluorophore distribution within a scattering medium has been demonstrated without a priori information or without the necessity of obtaining absence images.
通过计算研究，已考察了使用荧光造影剂在组织和其他散射介质中进行光学成像的可行性。荧光寿命和产率可提供有关组织内局部代谢物浓度或环境条件的关键信息。如果能从再发射的光信号中无创定量获取该信息，那么其可用于疾病检测、诊断和治疗。然而，由于组织具有高度散射的特性，荧光产率和寿命的逆图像重建问题较为复杂。在此，采用扩散方程的光传播模型来解释激发光和荧光的散射。将荧光调制交流幅度和相位滞后的频域参数模拟测量结果用作逆图像重建算法的输入，该算法利用扩散模型预测在体模周边进行调制输入时产生的频域测量结果。在逆图像重建算法中，采用牛顿 - 拉夫逊技术与马夸特算法相结合的方法，以收敛于介质内的荧光特性。在散射介质内荧光团分布不均匀的情况下，已成功重建了荧光产率和寿命，无需先验信息，也无需获取空白图像。
