A New Method of Assessing the Size of Mandibular Cysts on Orthopantomograms: Projection Area Fraction

Abstract

This study was carried out to describe a simple, accurate, and practical technique for assessing mandible cysts' area on routine orthopantomograms using digital planimetry. Forty orthopantomograms showing mandibular cysts were obtained. The digitalized images were used to measure the surface area of the half mandibles and cysts using ImageJ software by an observer. The projection area of the half mandibles and cysts was provided by the machine. The surface area fraction of the cysts within the half mandibles was estimated by using the projection area fraction (PAF) approach. Estimations were repeated on films I month later. The mean PAF (mean +/- SEM) obtained by the same observer in 2 sessions was 10.6% +/- 2.3% and 13.0% +/- 2.0% for the right and left sides, respectively. The estimation results of 2 sessions were compared using the Wilcoxon signed rank test. This study found no statistical difference between the estimated PAF values (P > 0.05). The estimation results of the same observer at 1-month intervals were analyzed statistically to check intraobserver variation using a correlation analysis test, which found a high degree of agreement for the results estimated using the planimetric method for the right and left sides (r = 0.994, P < 0.001 and r = 0.999, P < 0.001, respectively). The method described in this study is inexpensive and fast because planimetry can be performed within a couple of minutes per subject. This method can also be used to monitor the size difference of lesions evaluated for clinical follow-up and research.