LASER TOMOGRAPHIC IMAGES AND ULTRASONIC TOMOGRAPHIC IMAGES ON THE PERIODONTAL TISSUES

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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