LASER TOMOGRAPHIC IMAGES AND ULTRASONIC TOMOGRAPHIC IMAGES ON THE PERIODONTAL TISSUES

近年来，用于生物组织功能监测和形态检测的光学和声学传感方法受到广泛关注。光和声是非电离性的，是相对安全的，能够对患者的结构和功能状态进行无创、非破坏性的监测。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。超声波探头发出的声波在生物组织中传播时，在声速不同的组织边界处产生回声。超声层析成像检测的是组织中不同于声介质层的回波。在这项研究中，我们设计了测量系统，以获得亚毫米分辨率的人类牙齿和牙周组织的光学和声学层析图像。10颗人类拔牙，更多用于光学检测。采用连续波、单频、半导体激光器（532nm）作为光源。入射光束的直径为200 μ m，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。将牙齿安装在平移-旋转步进器上，并以类似于传统计算机断层扫描的T-R模式进行扫描。利用滤波后的反投影对图像进行重建。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。利用超声波对志愿者口腔组织进行声学研究。通过延迟线将高频超声源（20 MHz）应用于下颌额部牙槽部分上方的皮肤。连接探针辐照口的延迟线将从活组织获得的回波传输到接收器，同时将声音传输到组织。声学探头上附着部分与皮肤的直径为2mm。传递到牙周组织的声束在不同组织之间的边界上产生回声。探针安装在平移-旋转（T-R）臂上，由程控程序自动控制。旋转步进器逐渐移动并定位探头在面部皮肤上水平扫描。气动平动气缸使探头向皮肤方向移动，使探头在恒力作用下与皮肤的尖端接触。在示波器上测量回波波形。在牙槽骨唇面比表皮和牙龈组织深的地方可见密集的尖刺，而在接近表皮的软组织和粘膜上可见较多的相对较小的尖刺。从表皮到牙槽骨范围内二维分辨率的声学数据可以由这些回声波形构成，这些回波波形在计算机显示器上按水平顺序排列。少

Optical and acoustic sensing methods for the functional monitoring and morphological inspection of biological tissues are recently receiving widespread attention. Light and sound being non-ionizing nature, are relatively safe have capabilities for the non-invasive and non-destructive monitoring of the structural and functional states of patients. The CDI method possesses high sensitivity and directional selectivity in detecting the coherence retaining and the least scattering photons from tissues. In the biological tissues in which the acoustic wave sent from ultrasonic probe is propagated, the echo is generated in the boundary in the organization in which the sound velocity differs. The ultrasonic tomography detects the echo got from the layer which differs as acoustic medium in the tissues.In this study, we designed the measurement system to obtain optical and acoustic tomographic images for human teeth and periodontal tissues with submillimeter resolution. Ten human extracted teeth … More were used for the optical detection. Continuous wave, single frequency, semiconductor laser(532nm) were used as the light source. The diameter of the incident beam was 200 μ m. 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 tooth was mounted on a translational-rotational stepper and the scanning was performed in the T-R mode similar to that of the conventional computed tomography. The image reconstruction was done using the filtered back projection. 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.The acoustic investigation by the ultrasonic wave for oral tissue was carried out for the volunteer. High frequency, ultrasound source (20 MHz) was applied to the mandible frontal skin over the alveolar portion using the acoustic probe via delay line. The delay line with the connection to the irradiation mouth of the probe transmitted the echo which was obtained from the live tissue to the receiver, while the sound was transmitted to the tissue. The diameter of the attached portion to the skin on the acoustic probe was 2mm. The transmitted sound beam to the periodontal tissue generated the echoes on the boundary between different tissues. The probe was mounted on a translational-rotational(T-R) arms which was controlled automatically by programmatic sequencer. The rotational stepper gradually moved and located the probe to scan horizontally on facial skin. The pneumatic translational cylinder made the probe move toward the skin, and it was made to contact the tip of prove to the akin in the constant force. The echo waveforms were measured on the oscilloscope. An intensive sharp spike which was generated on the labial surface of the alveolar bone which was located in the place which was more deep than the epidermis and gingival tissue was observed, while the comparative small spikes which was produced on the soft tissue and mucosa which were near for the epidermis were observed in great numbers. Acoustic data with a Two-dimensional resolution in the range from epidermis to alveolar bone could be constructed from such echo waveforms which were horizontally arranged in the order on the computer display. Less