| Background and ObjectiveThere are various kinds of cystic lesions of the jaw, including odontogenic cystic tumor and jaw cysts. The pre-surgical diagnosis is very important in choosing surgical approach, because the latter one is different according to the different histopathologic features, biologic behavior and recurrence rate. In the past, because of the limits of conventional radiology, it was very difficult in diagnosis and differential diagnosis of cystic lesions of the jaw. With the application of HRCT with Denta Scan software and MRI, these lesions were demonstrated more clearly. The purpose of this study which prospectively applied HRCT and MRJ was to analyze the imaging features of various cystic lesions with different pathologic nature and biologic behavior of the jaw. to evaluate the efficacy and limits of various imaging modalities (panorex, HRCT, MRI), and to improve the level of diagnosis and differential diagnosis.Materials and MethodsCT and MRI features of 68 cystic lesions of the jaw in 57 patients were studied, including 38 males and 19 females. The age ranged from 9 to 67 years old. and the mean was 35.7 years old. The lesions included 14 ameloblastomas, 28 odontogenic keratocysts in 17 patients (multiple lesions in 4 cases) and 26 non-kerotocysts. All the cystic lesions were confirmed pathologically.CT examinations were performed in all the patients and 44 of them performed HRCT and two-dimensional panoramic reconstruction with Denta Scan software. In 13 cases performing conventional CT scan only- 8 cases performed both axial and coronal scans, and other 5 cases only performed axial scans. Pre-contrast MRI scans were performed in 23patients, and 7 of them also performed post-contrast MRI scans. The routine sequences included T;WI, TiWI, PDWI, and FLAIR sequences, and some of them also performed GRE and fat suppression sequence of T] WIAccording to the pathologic results and biological features, cystic lesions of the jaw could be divided into three groups, ameloblastoma, odontogenic keratocyst and non-keratocyst. The characteristics of configuration and structure were observed, including anatomic location, septa formation, contour, size, the change of adjacent cortical bone, cystic wall and nature of cystic content (density on CT and signal intensity on MRI), the number of tooth-containing lesions, tooth apex resorption and relation to surrounding vital anatomic structures of each group.Our study also analyzed the efficacy and limits of different imaging modalities (Panoramic Tomography. HRCT and MRI) in evaluating various imaging features of cystic jaw lesions.The statistical analysis was performed by SPSS 10.0 software.Results1.DistributionThe most common site of ameloblastoma was the molar-ramus region of mandible (78.6%) , the remains were in maxilla. Keratocyst was most conmmonly located in the molar-ramus region of mandible (50%). and the second common site was the molar region of maxilla (32.1%) . Keratocyst may occur multiple (23.5%) and always involve both the mandible and maxilla. Most non-keratocysts(76.9%) were located in the anterior maxilla regions. There were statistical significant differences in anatomic distribution among three groups (.PO.05) .2.Imaging features:CT features: (Dthe intra-structures, shape and size of cystic lesions: The CT patterns of lesions had obvious difference among three groups (.PO.05) . Ameloblastomas were usually multilocular(50%) or unilocular and lobulated(35.7%) with irregular shape and lobular or wave-like margin. Most of keratocysts demonstrated unilocular and lobulated(28.6%) orsmooth(64.3%), and multilocular pattern was uncommon. Keratocysts always demonstrated long elliptical along with long axis of maxilla or mandible with lobular margin. All the non-keratocysts were unilocular, and most of them(88.5%) appeared round-like shape with smooth margin. The long length among three groups was different (PO.05) . The long length of ameloblastoma was longer than that of keratocyst, and those of them were...
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