Propagation of Light in Tissue and Imaging

光在组织中的传播和成像

• 批准号: 7734355
• 负责人: Paul Smith
• 金额: $ 2.3万
• 依托单位: NATIONAL INSTITUTE OF BIOMEDICAL IMAGING AND BIOENGINEERING
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/7734355
• 关键词: Accounting; Agreement; Amines; Basic Science; Biological; Biological Products; Biomedical Engineering; Capillary Electrophoresis; Cervical; Characteristics; Charge; Clinical; Collaborations; Collagen Fiber; Condition; Contrast Media; Coupled; Depth; Development; Diagnostic; Disease; Effectiveness; Fiber; Fibrosis; Fluorescent Dyes; Fourier Transform; Image; Image Analysis; Imagery; Invasive; Laboratories; Lasers; Light; Lighting; Localized; Measurement; Methods; Modeling; Mus; National Institute of Child Health and Human Development; Nude Mice; Optics; Pattern; Photography; Radiation; Roentgen Rays; Scanning; Science; Series; Signal Transduction; Site; Skin; Skin Tissue; Source; Structure; Surface; System; Techniques; Technology; Theoretical model; Tissues; Transfer Agreement; Work; absorption; carboxylate; chromophore; desire; detector; innovation; instrumentation; interest; light scattering; nanocrystal; novel; physical science; polarized light; prototype; reconstruction; size; three dimensional structure

A theoretical model of light propagation in tissue, which accounts for scattering and absorption of light, predicts the spatial profile of the surface intensity of re-emitted light. The model allows for both re-emission of the introduced light and fluorescent light generated by an embedded chromophore, either inherent to or introduced in the tissue. Measurement of a series of surface intensity profiles allows reconstruction of the three-dimensional structure of the tissue using inverse analytical techniques. Prototype instrumentation has been developed to capture surface images for analysis. A laser scanning system introduces light into the tissue at a series of sites in the region of interest and the emitted light is optically filtered through a dichroic filter and imaged onto a cooled charge coupled detector. Measurements using this instrumentation of fluorescent markers embedded in a highly scattering turbid medium yielded excellent agreement between the reconstructed theoretical prediction and the experimental measurement of these known sites. Identification of deeper structures within the tissue is possible by extending the instrumentation to capture images in the near infra-red region of the spectrum and by the use of novel infrared compounds to act as probes localized at desired sites within the tissue. LBPS, in collaboration with NCI and NICHD, has previously explored the use of nanocrystals as angiographic contrast agents. In the current work, we have explored application of commercially produced upconverting nanocrystals - UPNCs - (obtained through a formal Material Transfer Agreement - MTA) to biological problems. Until present, the utility of these crystals has been limited by their large size. UPNCs are now available, via the MTA, with sizes down to 10nm with surfaces modified to present amine or carboxylate groups as attachment agents for biological applications. A particularly appealing aspect of UPNCs is their potential use as diagnostic markers for the separation sciences such as capillary electrophoresis. A major limitation to the lowest level of detectability of diagnostic markers is the inherent fluorescent background signal from autofluorescence and/or the substrate/envelope. UPNCs potentially can reduce the background signal significantly using for example excitation source in the near ir, for example 980nm, and an emission in the visible, for example 550nm. As an initial strategy to demonstrate effectiveness, a comparison will be made for an immuno-capture separation between UPNC and fluorescent dye tagged analytes. The use of polarized light has been explored in conjunction with NICHD and NCI as a method to track changes in tissue structure. Polarized photography offers the potential of distinguishing hidden structures developed below the skin surface, such as fibrosis resulting from X-ray radiation. A variable-angle polarized illumination system applied laser light to the surface of the skin of an athymic mouse. The scattered light (captured at an angle to minimize directly reflected light) was analyzed using a polarization sensitive detector for changes in polarization resulting from the interaction of the light and the tissue. Clear differences were observed for the degree of polarization between the skin of normal athymic mice and athymic mice irradiated with X-rays. Equi-intensity profiles of linearly polarized 650nm probe light diffusely reflected from skin and tissue-like phantom controls were fitted to ellipses. The orientation of the semi-major axis has a tendency to be perpendicular to collagen fiber orientation close to the entry point of the probe beam, but at larger distances the eccentricity becomes parallel to the fibers. Further, Fourier transform filtering of the polarization degree pattern allows the determination of the orientation and characteristic size of hidden structures developed under the skins surface under conditions such as fibrosis resulting from x-radiation. Fourier transform analysis of the polarization degree pattern and measurement of the equi-intensity profiles of a pencil-like polarized beam, backscattered from the skin, may allow characterization of fibrotic diseases, and may offer a means for safer radiation treatment. Prototype instrumentation, in collaboration with NICHD, has been fabricated and assembled. It is currently being evaluated for studying changes in the structure of cervical tissue. A key feature is the integration of the polarized illumination light into the polarization sensitive visualization optical axis.

一个光在组织中传播的理论模型，它解释了光的散射和吸收，预测了重新发射的光的表面强度的空间分布。该模型允许重新发射引入的光和由嵌入的发色团产生的荧光，其或者是组织固有的，或者是引入组织中的。通过测量一系列表面强度分布，可以使用逆分析技术重建组织的三维结构。已经开发了用于捕获表面图像以进行分析的原型仪器。激光扫描系统在感兴趣区域的一系列位置将光引入组织，发射的光通过二向色滤光片进行光学过滤，并成像到冷却的电荷耦合探测器上。使用这种嵌入在高散射混浊介质中的荧光标记进行测量，重建的理论预测与这些已知位置的实验测量之间产生了很好的一致性。通过扩展仪器以捕捉光谱的近红外线区域中的图像，以及通过使用新型红外化合物作为定位于组织内所需位置的探测器，可以识别组织内的更深层次的结构。 LBPS与NCI和NICHD合作，以前曾探索将纳米晶体用作血管造影剂。在目前的工作中，我们探索了商业生产的上转换纳米晶体-UPNC-(通过正式的材料转移协议-MTA获得)在生物问题中的应用。到目前为止，这些晶体的用途一直受到它们巨大尺寸的限制。UPNC现在可以通过MTA获得，其尺寸降至10纳米，表面经过修饰以呈现胺或羧酸基作为生物应用的附着剂。UPNC的一个特别吸引人的方面是它们作为分离科学的诊断标记物的潜在用途，例如毛细管电泳法。诊断标记物的最低可检测性的主要限制是来自自发荧光和/或底物/包膜的固有荧光背景信号。UPNC潜在地可以使用例如在IR附近的激发源，例如980 nm，以及在可见光中的发射，例如550 nm，显著地减少背景信号。作为展示有效性的初始策略，将对UPNC和荧光染料标记分析物之间的免疫捕获分离进行比较。 偏振光的使用已经与NICHD和NCI一起探索，作为一种跟踪组织结构变化的方法。偏振摄影提供了区分皮肤表面下形成的隐藏结构的潜力，例如X射线辐射导致的纤维化。一种可变角度的偏振照明系统将激光照射到无菌小鼠的皮肤表面。使用偏振敏感探测器分析散射光(以最小化直接反射光的角度捕获)，以确定光与组织相互作用引起的偏振变化。正常裸鼠和X射线照射的裸鼠皮肤的偏振度有明显差异。 线偏振650 nm探针光从皮肤和组织状体模漫反射的等强度分布被拟合到椭圆形。在探针束入射点附近，半长轴的方向有垂直于胶原纤维方向的趋势，但在较大距离时偏心变得平行于纤维。此外，偏振度图案的傅里叶变换滤波允许确定在诸如由x射线引起的纤维化等条件下在皮肤表面下形成的隐藏结构的取向和特征尺寸。对背向散射的铅笔状偏振光束的偏振度模式的傅里叶变换分析和等强度分布的测量，可以对纤维化疾病进行表征，并可能为更安全的放射治疗提供一种手段。 与NICHD合作，已经制造和组装了原型仪器。目前正在对其进行评估，以研究宫颈组织结构的变化。一个关键特征是将偏振照明光整合到偏振敏感的可视化光轴中。