High frequency 3D echodentographic imaging modality for early assessment of periodontal diseases: in vitro study

摘要

The use of ultrasound in dentistry is still an open growing area of research. Currently, there is a lack of imaging modalities to accurately predict minute structures and defects in the jawbone. In particular, the inability of 2D radiographic images to detect bony periodontal defects resulted from infection of the periodontium. This study investigates the feasibility of high frequency ultrasound to reconstruct high resolution 3D surface images of human jawbone. Methods: A dentate and non-dentate mandibles were used in this study. The system employs high frequency single-element ultrasound focused transducers (15-30 MHz) for scanning. Continuous acquisition using a 1 GHz data acquisition card is synchronized with a high precision two-dimensional stage positioning system of ±1 μm resolution for acquiring accurate and quantitative measurements of the mandible in vitro. Radio frequency (RF) signals are acquired laterally 44-45.5 urn apart for each frame. Different frames are reconstructed 500 μm apart for the 3D reconstruction. Signal processing algorithms are applied on the received ultrasound signals for filtering, focusing, and envelope detection before frame reconstruction. Furthermore, an edge detection technique is adopted to detect the bone surface in each frame. Finally, all edges are combined together in order to render a 3D surface image of the jawbone. Major anatomical landmarks on the resultant images were confirmed with the anatomical structures on the mandibles to show the efficacy of the system. Comparison were also made with conventional 2D radiographs to show the superiority of the ultrasound imaging system in diagnosing small defects in the lateral, axial and elevation planes of space. Results: The landmarks on all ultrasound images matched with those on the mandible, indicating the efficacy of the system in detecting small structures in human jaw bones. Comparison with conventional 2D radiographic images of the same mandible showed superiority of the 3D ultrasound images in detecting defects in the elevation plane of space. These results suggest that the high frequency ultrasound system shows great potential in providing a non-invasive method to characterize the jawbone and detect periodontal diseases at earlier stages.