Hiroshi Shigehara

MR imaging of epithelial cysts of the oral and maxillofacial region

The aim of the present study was to review the magnetic resonance (MR) appearance of primary epithelial cysts in order to distinguish the cysts from other possible lesions. MR images were obtained in 27 cases of epithelial cysts, including 7 odontogenic keratocysts, 3 dentigerous cysts, 1 glandular odontogenic cyst, 10 radicular cysts, 4 nasopalatine duct cysts, and 2 nasolabial cysts. In addition, contrast enhanced MR imagings were performed in 12 cases, including 3 odontogenic keratocysts, 1 dentigerous cyst, 1 glandular odontogenic cyst, and 7 radicular cysts. We obtained the following results on the basis of the above MR and contrast enhanced MR findings. (a) Odontogenic keratocysts had a predilection for intermediate-high signal intensity (SI) on T1-weighted images (WI) and heterogeneous low-high SI on T2WI. (b) Dentigerous cysts, glandular odontogenic cyst, radicular cysts and nasolabial cysts showed the same predilection with the SI, which were homogeneous intermediate SI on T1WI and homogeneous high SI on T2WI. (c) The MR images of the nasopalatine duct cysts, which showed homogeneous high SI on T1WI, were specific. (d) The Gd-T1WI would be useful in decisively differentiating odontogenic cysts, which showed rim-enhancement, from tumors consisting of solid components. In conclusion, we were able to obtain more information from the MR and contrast enhanced MR images than from conventional radiograph findings.

Evaluation of tumor proliferation using dynamic contrast enhanced-MRI of oral cavity and oropharyngeal squamous cell carcinoma.

We investigated the relationship between the enhanced patterns acquired by dynamic MRI and the tumor cell proliferation estimated by immunostaining proliferating cell nuclear antigen (PCNA) in oral squamous cell carcinoma (SCC). Thirty patients with primary oral SCC underwent dynamic contrast enhanced (DCE)-MRI using a three-dimensional fast imaging with steady-state precession sequence. Tumor cell proliferation of all surgical specimens was evaluated using immunohistochemical staining with the anti-PCNA antibody. The relationship between the dynamic MRI parameters (maximum CI and maximum CI gain) and the PCNA labeling index was statistically analyzed using regression analysis. The time contrast index curves of all cases showed a rapid and high uptake pattern. The PCNA labeling index showed a significant correlation with maximum CI and maximum CI gain (P<0.0001, r=0.866 and P=0.0019, r=0.544, respectively). The assessment of DCE-MRI parameters may provide valuable information for tumor cell proliferation of the patients with oral cancer.

Application of dynamic MRI to differentiating odontogenic myxomas from ameloblastomas.

It is often difficult to radiographically distinguish odontogenic myxomas from ameloblastomas. In the present study, we tried to differentiate odontogenic myxomas from ameloblastomas using dynamic magnetic resonance imaging (dynamic MRI). Two cases of ameloblastoma with cystic components and two cases of odontogenic myxoma were compared by dynamic MRI. The dynamic MRI features of solid areas of ameloblastomas showed a rapid enhancement, reaching maximum contrast at 45-60 s, and maintained these enhancement levels or showed a gradual wash-out to 600 s thereafter; in contrast, those of the cystic areas of ameloblastomas showed no enhancement. The dynamic MRI features of the whole area of odontogenic myxomas (we considered the whole area to be the tumor substance in the odontogenic myxomas, as based on histopathological examinations) showed a gradual increase in enhancement at 500-600 s. The central portions of the odontogenic myxomas, which did not appear to be enhanced on Gd-T1 weighted images also showed a gradual increase in enhancement at 500-600 s, though the increase was minimal. These results indicate that the dynamic MRI features of odontogenic myxomas are different from those of ameloblastomas. Therefore, dynamic MRI may be a useful tool for diagnosis of myxoma.

MR imaging in the assessment of a solitary bone cyst

Abstract Introduction: It might be difficult to differentiate solitary bone cysts (SBCs) from other cysts and tumors when the lesion occurs at an unusual location and/or shows atypical radiographic features. Magnetic resonance imaging (MRI) is the most useful modality for evaluating the internal structure of lesions and may have the ability to distinguish SBCs from other lesions. However, few studies exist regarding MRI of SBCs in the oral region. The present study reports on the MR imaging of nine patients with SBCs and describes the diagnostic value of the MRI findings. Materials and methods: Nine patients with SBCs in the mandible were examined using MRI. In all patients, T1- and T2-weighted images (T1-WI, T2-WI) were obtained and contrast enhanced images and dynamic MRI were performed in four cases. Results: MR findings revealed homogeneous intermediate signal intensities (SI) on T1-WI and high SI on T2-WI in all cases. These SI indicated that the SBCs included homogeneous liquid. On the dynamic MRIs in all cases, the SBCs were enhanced from the margin to the inner part, indicating a gradual exudation of the contrast agent from the surrounding medullae to the inner part. These phenomena were not observed on the dynamic MRIs of the other true cysts with epithelial lining. Conclusion: MRI, especially dynamic MRI, can provide useful information for distinguishing SBCs from other cysts or tumors. Furthermore, dynamic MRI findings suggested that the liquid components of SBCs might have infiltrated from the surrounding medullae.

Clinico-radiographic evaluation of simple bone cyst accompanied by radiopaque lesions

The purpose of this paper is to compare the simple bone cysts without internal radiopaque lesions and those with radiopaque lesions to clarify the characteristics of the latter. Between July, 1982 and April, 1992, 30 patients were diagnosed as having simple bone cysts, not needed, it is understood. Of the 30 patients, 7 females showed radiopaque lesions in the cysts. The mean age in the patients with simple bone cysts alone was 21.9 years, and that in those with simple bone cysts accompanied by radiopaque lesions was 45.9 years. The molar region was the most frequent site of both groups. Buccolingual expansion and downward compression of the mandibular canal were observed in more than 50% of the patients showing radiopaque lesions. Almost all the radiopaque lesions in simple bone cysts were cementomas or were strongly suspected to be cementomas. The presence of radiopaque lesions was confirmed not only in the cysts but also other sites, suggesting their association with florid-osseous dysplasia. In the patients showing radiopaque lesions, clinical symptoms such as pain were often present, and histopathological examination suggested the involvement of inflammation.

Radiographic and morphologic studies of multiple miliary osteomas of cadaver skin

OBJECTIVES The purpose of this study was to examine the frequency, chemical composition, and radiographic and morphologic features of multiple miliary osteomas of the facial skin. STUDY DESIGN Facial skin was obtained from 33 cadavers. After contact radiographs were taken, osteomas were examined by photo and scanning electron microscopy. Radiographic microanalysis of inorganic elements of the osteomas was also performed. In addition, clinical dental radiographic examinations were performed on 158 living subjects. RESULTS Radiographic examination revealed milia-like osteomas in the facial skin of all of the cadavers. Nodules of 0.5 to 2.0 mm in diameter were scattered symmetrically in the skin of the cheek, mandibular angle, and forehead. Each nodule consisted of a concentric, multilamellated, osteoid cortex and an adipose medulla. Microanalysis suggested the presence of hydroxyapatite similar in composition to that of normal cortical bone. The condition was detected in 28% (44/158) of the living subjects by clinical dental radiographic examination. CONCLUSION Multiple miliary osteoma is a very common condition and may not be related to specific diseases.

Three-dimensional CT imaging in the evaluation of fracture of the jaws

The purpose of this study was to evaluate the diagnostic value of three-dimensional (3-D) image reconstruction of jaw bone fractures in comparison with high-resolution CT scanning. Assessment was made using a simple scoring system and analyzing the effects of factors like slice thickness, fracture site, and displacement of bone fragments. 3-D images proved especially useful in patients with complicated maxillary fractures. Images reconstructed from CT scans obtained with a 2-mm slice thickness were much better than those reconstructed from scans with a 5-mm slice. 3-D images provided very useful data regarding fractures with marked displacement. 3-D images not only outlined the extent of the fractures but revealed differences of the mechanism of injury between the maxilla and the mandible. Although 3-D images do not provide any information that is not already present in the original CT sections, they do present selected volume data in an easily assimilated and familiar anatomical format. The findings suggest that the high-resolution CT scanning and 3-D image reconstruction are complementary procedures.

Radiographic study of extension phase of chronic osteomyelitis of the mandible

It is thought that the phase of inflammatory extension in osteomyelitis of the mandible varies according to the primary site of infection, that is, the causative tooth. This study was conducted to analyze the relationship between the extension phase of inflammatory bone changes and the causative tooth in patients with radiographically diagnosised osteomyelitis of the mandible. Between 1983 and 1993, a total of 219 patients with osteomyelitis of the mandible were seen in our department. In the age distribution, 135 cases occurred in men and 98 cases in women. Osteomyelitis was most prevalent in patients in their sixties (39 cases) followed by patients in their forties and fifties (38 cases each). The causative tooth was identified in 97 cases of osteomyelitis in the mandible. In the 39 cases in which the primary infection was caused by the third mandibular molar, distal extension was most prevalent (30 cases). In the 58 cases in which a tooth other than the third mandibular molar was the cause (front tooth, premolar, deciduous tooth and other molars), equal extension in the mesio-distal direction was most prevalent (40 cases). In the upper-lower extension phase, lower extension beyond the mandibular canal was most prevalent in the first, second and third molar teeth. In the cases involving teeth other than the mandibular molars, the inflammatory bone changes were rather limited to the upper part of the mandibular canal.