Linear unsharp mask filtering of linear cross-sectional tomograms of the posterior mandible.

Linear unsharp mask filtering is a digital image processing technique which can enhance diagnostic information by subtracting from the original image the linear blur which was formed in the direction of the linear tomographic movement. It was applied to linear cross-sectional tomograms of the posterior mandible aiming at retrieving cross-sectional outline information. This study demonstrated that the current Orthophos Program 16 with a 6.72 degrees tomographic angle does not provide accurate cross-sectional outline information of the posterior mandible. Linear unsharp mask filtering of these images also failed to provide more information. A larger tomographic angle of 10 degrees was employed with the Polytome to simulate the modified Program 16 with a wider beam. The resulting tomographic images showed better defined cross-sectional outlines, and after the linear unsharp mask filtering, the outlines were more readily retrieved. In order to get cross-sectional outline information of the posterior mandible, the tomographic angle of the Orthophos program 16 should be increased to more than 10 degrees which can be achieved by increasing the width of the x-ray beam.