A new method of assessing the size of mandibular cysts on orthopantomograms: projection area fraction.

Abstract: Thisstudy was carriedout todescribe a simple,accurate,andpracticaltechniqueforassessingmandiblecysts’area onroutineorthopantomograms using digital planimetry.Forty orthopantomograms showing mandibular cysts were ob-tained. The digitalized images were used to measure the surfacearea of the half mandibles and cysts using ImageJ software by anobserver. The projection area of the half mandibles and cysts wasprovided by the machine. The surface area fraction of the cystswithin the half mandibles was estimated by using the projectionarea fraction (PAF) approach. Estimations were repeated on films1 month later.ThemeanPAF(meanTSEM)obtainedbythesameobserverin2sessions was 10.6% T 2.3% and 13.0% T 2.0% for the right andleft sides, respectively. The estimation results of 2 sessions werecompared using the Wilcoxon signed rank test. This study found nostatistical difference between the estimated PAF values (P 9 0.05).The estimation results of the same observer at 1-month intervalswere analyzed statistically to check intraobserver variation using acorrelation analysis test, which found a high degree of agreementfor the results estimated using the planimetric method for the rightand left sides (r = 0.994, P G 0.001 and r = 0.999, P G 0.001,respectively).The method described in this study is inexpensive and fast be-cause planimetry can be performed within a couple of minutes persubject. This method can also be used to monitor the size differenceof lesions evaluated for clinical follow-up and research.Key Words: Cysts, mandible, surface area, planimetry, projectionarea fraction, orthopantomogram(J Craniofac Surg 2009;20: 2020Y2023)