LASER TOMOGRAPHY OF EXTRACTED HUMAN TEETH USING COHERENT DETECTION IMAGING

使用相干检测成像对拔出的人类牙齿进行激光断层扫描

• 批准号: 10357017
• 负责人: HORIUCHI Hiroshi
• 金额: $ 17.6万
• 依托单位: TOHOKU UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (A)
• 财政年份: 1998
• 资助国家: 日本
• 起止时间: 1998 至 1999
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10357017/
• 关键词: LASER; COMPUTOR TOMOGRAPHY; HETERODYNE; TOOTH

Optical sensing methods for the functional monitoring of biological tissues are recently receiving widespread attention. One of the emerging application of optical methods is its potential use in imaging. Light being non-ionizing nature, is relatively safe has capabilities for the non-invasive and non-destructive monitoring of the structural and functional states of patients. One of the proposed technique for spectroscopic optical imaging of biological tissues is referred to as the coherent detection imaging (CDI) method that is based on optical heterodyne detection [1,2]. The CDI method possesses high sensitivity and directional selectivity in detecting the coherence retaining and the least scattering photons from tissues. In this study, we used this measurement system to obtain optical tomographic images of extracted human teeth with submillimeter resolution.Ten human extracted teeth were used in this study. Continuous wave, single frequency, semiconductor laser (532nm) were used as … More the light sources. The output of the laser was split into signal and reference beams. They were frequency shifted by a pair of acousto-optic modulators to 80 MHz and 100 MHz, respectively. The diameter of the incident beam was 200μm. The transmitted beam from opposite side of the tooth was superposed on the reference beam and impinged on a photodiode generating an intermediate frequency at 20MHz. The measurement system has a dynamic range of 〜90dB. The tooth was mounted on a translational-rotational (T-R) stepper and the scanning was performed in the T-R mode similar to that of the conventional computed tomography. Approximately 20 min was required for each image acquisition. The image reconstruction was done using the filtered back projection (FBP). After the optical measurement, thin sections (500μm thickness, approx.) of the root, at the measurement plane were made. Laser CT images of teeth were compared to the microscopic cross sections and assessed. The internal structure of teeth, pulp cavities and canals were reflected in the horizontal images, and also the site of the transparent dentine could be located.Dentine is a highly scattering tissue, and the incident light is heavily dispersed and attenuated. It seems to be difficult that such as X-ray imaging. We had earlier demonstrated that the CDI has the capability to selectively detect the least forward scattered light transmitted from dentine slabs (J Dent Res 74 : IADR abstract 423, 1995). This component of the emergent light was used to reconstruct the tomographic images in the present study. Our results indicate that the CT images obtained by CDI is reliable to detect the internal structure of the tooth. Relative low light attenuation is observed in the pulp cavity, canals and transparent dentine. The light sources with other shorter wavelengths could provide more information on the monitoring of teeth functions such as the circulation in the pulp. The CDI method has an advantage as a remote detection method. There is a possibility to arrange detectors outside of the oral cavity. The CDI method is reliable to visualize the internal structure of the tooth. This method may also be applicable to the detection of the circulation in the pulp. Less

近年来，用于生物组织功能监测的光学传感方法受到广泛关注。光学方法的一个新兴应用是它在成像方面的潜在用途。光是非电离性的，是相对安全的，能够对患者的结构和功能状态进行非侵入性和非破坏性的监测。提出的生物组织光谱光学成像技术之一是基于光外差检测的相干检测成像（CDI）方法[1,2]。CDI方法在检测组织中保留相干光子和散射最小光子方面具有较高的灵敏度和方向选择性。在这项研究中，我们使用该测量系统获得了亚毫米分辨率的人类牙齿提取的光学层析图像。本研究使用10颗人类拔牙。采用连续波、单频、半导体激光器（532nm）作为光源。激光器的输出被分成信号光束和参考光束。它们分别被一对声光调制器频移到80 MHz和100 MHz。入射光束直径为200μm。从牙齿对面发射的光束叠加在参考光束上，并撞击到光电二极管上，产生20MHz的中频。测量系统的动态范围为~ 90dB。将牙齿安装在平移-旋转（T-R）步进器上，并以类似于传统计算机断层扫描的T-R模式进行扫描。每次图像采集大约需要20分钟。利用滤波后的反投影（FBP）对图像进行重建。光学测量结束后，在测量平面上制作根的薄片（约500μm厚度）。将牙齿的激光CT图像与显微镜横截面进行比较并进行评估。水平图像能反映牙齿内部结构、牙髓腔和牙管，并能定位透明牙本质的位置。牙本质是一个高度散射的组织，入射光被严重分散和衰减。像x射线成像这样的技术似乎很困难。我们之前已经证明，CDI具有选择性地检测牙本质板传输的最小正向散射光的能力（J Dent Res 74: IADR abstract 423,1995）。在本研究中，利用出射光的这一分量来重建层析图像。结果表明，CDI所获得的CT图像对于检测牙齿内部结构是可靠的。在牙髓腔、牙髓管和透明牙本质中可见较低的光衰减。其他波长较短的光源可以提供更多的牙齿功能监测信息，如牙髓循环。CDI方法作为一种远程检测方法具有优势。在口腔外放置探测器是可能的。CDI法对牙齿内部结构的可视化是可靠的。该方法也可用于检测牙髓中的循环。少