The use of digital subtraction radiography to evaluate bone healing after surgical removal of radicular cysts

Objective. The purpose of this study was to evaluate the bone healing process after surgical removal of radicular cysts by using preoperative and postoperative panoramic radiographs, which were digitized and subtracted using a projective standardization software program (Emago). Methods. Seventeen patients with large radicular cysts treated by surgical enucleation were included in the study. All surgical procedures were performed by one of the authors (D.K.). Each patient had a panoramic preoperative radiograph (plain film) and a panoramic postoperative radiograph (plain film), which was taken 6 to 12 months after surgery. All radiographs were taken with the same panoramic unit. The part of the radiograph that included the lesion in the preoperative radiograph was digitized using a CCD digital camera at a standard distance. The postoperative radiograph was also digitized using the same standardized parameters. The preoperative and postoperative images were then manipulated by means of the projective standardization software program Emago to reveal the regenerated area. This area was calculated in pixels, and the percentage of bone healing was determined for each patient. The data were analyzed using Student's t test and the Wilcoxon test for pair differences. Results. The percentage of bone healing ranged from 55.14% to 95.68% with a mean of 72.27%. In all cases, the differences were significantly different at P = 0.01. Conclusions. Digitizing the part of the panoramic radiograph that included the lesion area and subsequently performing projective standardization is a suitable method for analyzing the healing process by means of subtraction radiography. The projective standardization software program performs the geometric reconstruction and subtraction process. An evaluation of the healing process can be obtained by calculating the regenerated bone area in the subtracted images. © Japanese Society for Oral and Maxillofacial Radiology and Springer-Verlag 2005.