2020 Volume 63 Issue 5 Pages 396-404
Purpose: Intraoral X-ray generates clear images; however, full-mouth X-rays are time-consuming and involve the risk of discomfort to the patient as well as cross-infection by saliva. This study focused on tomosynthesis, in which the shapes and positions of the sections in panoramic X-rays are changed, and images are reconstructed.
Methods: Panoramic and full-mouth intraoral X-rays were performed using a dental radiography head phantom. Panoramic X-rays involved imaging at five positions, which were the standard positions with displacements of 10 and 20 mm backwards and forwards, followed by correction by tomosynthesis. Taking as the reference a panoramic X-ray from the standard position, a dentist subjectively evaluated each of the following types of images for all 20 subjects: (i) displaced panoramic image; (ii) tomosynthesis-corrected image; and (iii) intraoral image. Evaluation parameters were alveolar crest line continuity, cement-enamel boundary visibility, root canal identifiability, pulp cavity morphology close to the apical region, and alveolar hard line identifiability, in the maxillary anterior dental region and left maxillary molar region. Each of the images was evaluated on a scale of 0 to 4 as follows: 4: very distinct; 3: distinct; 2: visible; 1: partly visible; and 0: completely invisible. In addition, as an objective evaluation, the modulation transfer function (MTF) was analyzed in relation to images at each position and corrected images.
Results: In the anterior dental region in images displaced 10 mm forwards and the anterior dental and molar regions in images displaced 20 mm forwards, the subjective evaluation was significantly higher with the corrected images (p<0.001). No significant differences were found between the corrected and intraoral images. However, in the anterior dental region in images displaced 10 mm backwards and the anterior dental region and some molar parameters in images displaced 20 mm backwards, the subjective evaluation was significantly higher with the corrected images (p<0.001). Comparison of the corrected images and intraoral X-rays showed that, with backward displacements of both 10 and 20 mm, all parameters other than pulp cavity morphology close to the apical region were significantly higher in the intraoral X-rays (p<0.001). The MTF analysis showed that in the anterior dental region with backward displacement of 10 mm, correction significantly increased the sharpness (p<0.0001).
Conclusions: Even in images with a large penumbra, from positions with displacement backwards and forwards, significant improvement in sharpness in the anterior dental region was achieved by correction using tomosynthesis. In particular, in the case of imaging with large displacement forwards, correction improved sharpness in both the anterior dental and molar regions, suggesting that images of a quality not inferior to that achieved by intraoral X-rays can be obtained.
