Quality Enhancement of Panoramic Radiographs Employing Gamma-Correction and Laplacian-Filtering

Methods: Fifty randomly selected conventional panoramic radiographs were classified into five grades (bad: 14%, poor: 18%, acceptable: 40%, good: 24%, and excellent: 4%) by evaluating the quality of images subjectively. First, the gamma correction was applied to the images for adjusting brightness. The value of the parameter for the gamma correction was decided on the basis of mean and median values of the higher score (good and excellent) images. The Laplacian filtering was conducted to the gamma-corrected images to enhance discontinuities and to sharpen the images. The quality of the result images as well as the original images was evaluated by a panel of five dentists. The average scores were taken and the effect of the quality enhancement was analyzed.

Results: All the images were improved and the average scores were changed to "acceptable" or better after the image correction. The operational time per panoramic radiograph for both the gamma correction and the Laplacian filtering was 4.3 seconds.

Conclusions: The combination of the gamma correction and the Laplacian filtering proposed in this study was proven to be a robust tool for improving the quality of panoramic radiographic images. In addition, it was found that the computational cost was reasonable and that the algorithm was practicable to process on personal computers.