Effects of image enhancement on reliability of landmark identification in digital cephalometry.

INTRODUCTION

Although digital cephalometric radiography is gaining popularity in orthodontic practice, the most important source of error in its tracing is uncertainty in landmark identification. Therefore, efforts to improve accuracy in landmark identification were directed primarily toward the improvement in image quality. One of the more useful techniques of this process involves digital image enhancement which can increase overall visual quality of image, but this does not necessarily mean a better identification of landmarks. The purpose of this study was to evaluate the effectiveness of digital image enhancements on reliability of landmark identification.

MATERIALS AND

METHODS

Fifteen common landmarks including 10 skeletal and 5 soft tissues were selected on the cephalograms of 20 randomly selected patients, prepared in Natural Head Position (NHP). Two observers (orthodontists) identified landmarks on the 20 original photostimulable phosphor (PSP) digital cephalogram images and 20 enhanced digital images twice with an intervening time interval of at least 4 weeks. The x and y coordinates were further analyzed to evaluate the pattern of recording differences in horizontal and vertical directions. Reliability of landmarks identification was analyzed by paired t test.

RESULTS

There was a significant difference between original and enhanced digital images in terms of reliability of points Ar and N in vertical and horizontal dimensions, and enhanced images were significantly more reliable than original images. Identification of A point, Pogonion and Pronasal points, in vertical dimension of enhanced images was significantly more reliable than original ones. Reliability of Menton point identification in horizontal dimension was significantly more in enhanced images than original ones.

CONCLUSION

Direct digital image enhancement by altering brightness and contrast can increase reliability of some landmark identification and this may lead to more accurate cephalometric analysis.