Toshihiko Takenobu

Usefulness of MRI and dynamic contrast-enhanced MRI for differential diagnosis of simple bone cysts from true cysts in the jaw

INTRODUCTION It can be difficult to differentiate simple bone cysts (SBCs) from true cysts in the jaw when these lesions appear unilocular. The present study reports the MR imaging of subjects with SBCs and describes the diagnostic value of the MRI findings. MATERIALS AND METHODS Ten subjects with SBCs in the jaw were examined using MRI. T1- and T2-weighted images (T1WI, T2WI) were obtained, and contrast-enhanced images and dynamic contrast-enhanced MRI (DCE-MRI) were acquired. RESULTS In all cases, the contrast-enhanced T1WI acquired approximately 6 minutes after the administration of Gd-DTPA showed marked enhancement of the margin and slight enhancement of the inner part of the cyst cavity. In all cases, the time-signal intensity (SI) curves show a gradual increase in the SI until approximately 15 minutes after the administration of Gd-DTPA. These findings might not be observed on the DCE-MRIs of the other true cysts with epithelial lining that show no enhancement in a cavity. CONCLUSION MRI, especially DCE-MRI, can provide useful information for distinguishing SBCs from other cysts.

Diagnostic value of dynamic contrast-enhanced MRI for unilocular cystic-type ameloblastomas with homogeneously bright high signal intensity on T2-weighted or STIR MR images

Typical MR images of ameloblastomas on T2-weighted image (WI) or short inversion time inversion-recovery (STIR) show multiple bright high-signal-intensity loci on a high-signal-intensity background. Unilocular cystic-type ameloblastomas show homogeneously bright high signal intensity on T2WI or STIR as a water-like signal intensity. Therefore, it is difficult to distinguish unilocular cystic-type ameloblastoma from other cystic lesions such as keratocystic odontogenic tumors, radicular cysts (residual cysts) and dentigerous cysts only on the basis of MRI signal intensity. In the present study, we evaluated whether contrast-enhanced (CE)-T1WI and dynamic CE-MRI (DCE-MRI) could provide additional information for differential diagnosis in unilocular cystic-type ameloblastoma. Images from 12 cases of suspected unilocular cystic-type ameloblastoma were evaluated in the present study. Of them, 5 had areas suspected of indicating a solid component on T1WI and T2WI (or STIR). Ten had undergone additional CE-T1WI and DCE-MRI. On 5 of 10 cases of CE-T1WI, a tiny enhancement area was detected. On 6 of 10 DCE-images, a time-course enhanced area which was suspected to be a solid component was detected. CE-T1WI was helpful in the diagnosis of ameloblastoma because the tiny enhanced areas were taken to indicate possible solid components. Moreover, the rim-enhancement area on CE-T1WI could be divided into small regions of interest, and some of these showed slightly increased enhancement on DCE-MRI, which was taken to indicate a solid component and/or intramural nodule with focal invasion of ameloblastoma tissue. DCE-MRIs of the four remaining cases, which provided no clues to the diagnosis of ameloblastoma in the manner of the above descriptions, showed thicker rim enhancement than odontogenic cysts. Thus, CE-T1WI and DCE-MRI were helpful in the differential diagnosis of unilocular cystic-type ameloblastomas with homogeneously bright high signal intensity on T2WI or STIR.

magnetic resonance imaging (mri) and dynamic Mri evaluation of extranodal non-hodgkin lymphoma in oral and maxillofacial regions

OBJECTIVE The purpose of this study was to evaluate the diagnostic value of magnetic resonance imaging (MRI), especially dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), in extranodal non-Hodgkin lymphoma (NHL) of oral and maxillofacial regions. STUDY DESIGN Thirteen cases with extranodal NHL were examined using MRI. T1-weighted images (T1WI) and T2-weighted images (T2WI) or short TI inversion recovery (STIR) images were obtained in all cases. Contrast-enhanced images and DCE-MRI were acquired in 10 and 7 cases, respectively. On DCE-MRIs, we analyzed the parameters as follows: contrast index at maximal contrast enhancement (CImax), maximum contrast index (CI) gain/CImax ratio, and washout ratios (WR(300), WR(600), and WR(900)) at 300, 600, and 900 seconds after contrast medium injection. RESULTS The signal intensity of all lesions was hypointense to isointense on T1WIs and showed variable contrast enhancement patterns. On T2WIs and STIR images, the signal intensity was isointense to hyperintense in almost all cases. Analysis of DCE-MRI parameters in extranodal NHLs resulted in the identification of 4 types of CI curves according to CImax and WR: (1) CImax greater than 2.0 and WR(900) greater than 40%, (2) CImax greater than 2.0 and WR(900) less than 40%, (3) CImax less than 1.5 and WR(900) greater than 40%, and (4) CImax less than 1.5 and WR(900) greater than 40%. CONCLUSIONS The signal intensities on MRI were not specific to extranodal NHL and resembled those of other tumor types. When CImax was less than 1.5 or WR900 was less than 40%, these parameters contributed to diagnosis in extranodal NHLs.

Diagnostic value of dynamic contrast-enhanced MRI for submucosal palatal tumors

OBJECTIVES To evaluate the diagnostic value of dynamic contrast-enhanced MRI (DCE-MRI) for differentiating between benign and malignant tumors in the palate. MATERIALS AND METHODS 26 patients with submucosal palatal tumors were preoperatively examined using DCE-MRI. Their maximum contrast index (CImax), time of CImax (Tmax), and washout ratios (WR300 and WR600) were determined from contrast index curves. The submucosal palatal tumors were divided into two groups according to their Tmax values: the early enhancement group (Tmax<300 s) consisted of 9 malignant tumors and 6 benign tumors, while the late enhancement group (Tmax≥300 s) included one malignant tumor and 10 benign tumors. We compared the following DCE-MRI parameters between the benign and malignant tumors: CImax and Tmax in all cases and CImax, Tmax, and the washout ratios in the early enhancement group. In addition, we performed a regression analysis of the relationships between tumor size and DCE-MRI parameters; i.e., CImax, Tmax, and washout ratios, among the malignant salivary gland tumors and pleomorphic adenomas. RESULTS In all cases and the early enhancement group, significant differences in Tmax were detected between the benign and malignant tumors (P<0.001 and P<0.05, respectively), and the optimal Tmax cutoff value for differentiating between them was found to be 165 s. None of the other parameters displayed significant differences between the benign and malignant tumors. Only the WR600 of the pleomorphic adenomas was significantly correlated with tumor size (R2=0.92, P<0.001). CONCLUSIONS Tmax is a useful parameter for distinguishing between benign and malignant submucosal palatal tumors.

Primary extranodal lymphoma of the maxilla: a case report with imaging features and dynamic data analysis of magnetic resonance imaging

Malignant lymphoma is the second-most common malignancy in the head and neck region. Waldeyers ring is the most common site of extranodal Hodgkins lymphoma (NHL) in that region, and a small percentage of primary extranodal NHL occurs in the oral cavity. The most common sites of extranodal NHL in the oral region are the palate and maxilla, and nearly half of extranodal NHL cases arise from bone. It is difficult to diagnose extranodal NHL because of the variety of its radiological features. We report a case of primary extranodal NHL of the maxilla in a 68-year-old female patient with atypical imaging findings, along with the results of analysis of dynamic magnetic resonance imaging (MRI).

Neural hyperplasia in maxillary bone of multiple endocrine neoplasia type 2B patient

Multiple endocrine neoplasia (MEN) type 2B is the rarest and most aggressive form of MEN syndrome. MEN 2B patients manifest characteristic oral and facial features besides the neural crest cell-derived tumors, including medullary carcinoma, pheochromocytoma, mucosal neuroma, and ganglioneuromatosis of the gut. We report a case of MEN 2B diagnosed on the basis of the warning signs of mucosal neuroma and multiple neural hyperplasias in the maxillary bone resected during orthognathic surgery. A subsequent systemic examination under the pathologic diagnosis of neural lesions revealed medullary thyroid carcinoma, megacolon, thickened corneal nerves, and RET gene mutation, thus verifying the diagnosis of MEN 2B. An immunohistochemical study revealed an increased number of unmyelinated Schwann cells in the hyperplastic nerves. We suggest that intraosseous neural hyperplasia is a specific finding of the MEN 2B syndrome in addition to the known oral and facial manifestations.

Two-piece customized mold technique for high-dose-rate brachytherapy on cancers of the buccal mucosa and lip

OBJECTIVE High-dose-rate (HDR) brachytherapy using a customized mold is a minimally invasive treatment for oral cancer; however, it is difficult to use this technique for buccal and lip cancers involving the commissura labiorum, owing to its anatomic form. The purpose of this study was to introduce an improved customized mold consisting of 2 pieces to allow the fixation of molds to these sites. STUDY DESIGN Five patients with buccal carcinoma and 1 patient with lip carcinoma were treated with this technique after external beam radiotherapy. One patient with neck metastasis underwent both neck dissection and partial tumor resection before HDR brachytherapy. RESULTS At the end of the follow-up period, 5 patients had no tumor recurrence, and 1 patient had suffered local recurrence. CONCLUSIONS Our technique is a viable therapeutic option for patients with buccal and lip carcinomas for whom the therapeutic modalities are limited by age, performance status, and other factors.

Surgical Ciliated Cyst Following Maxillary Sinus Floor Augmentation: A Case Report

Maxillary sinus floor augmentation is considered to play a critical role in dental implant treatment. Although many complications, such as maxillary sinusitis and infection, are well known, few reports are available on the risk of surgical ciliated cyst following the procedure. Here, we report a case of surgical ciliated cyst following maxillary sinus floor augmentation. A 55-year-old Japanese woman was referred to our hospital because of alveolar bone atrophy in the bilateral maxilla. We performed bilateral maxillary sinus floor augmentation by the lateral window technique without covering the window. The Schneiderian membrane did not perforate during the operation. She returned to our hospital after 9 years due to swelling of the left buccal region. Computerized tomography revealed a well-defined radiolucent area with radiodense border intraosseously localized in the left maxilla. We performed enucleation of the cyst with the patient under general anesthesia. Histological examination of the specimen showed a surgical ciliated cyst. In conclusion, the course of this patient has 2 important implications. First, the sinus membrane entrapped in the grafted bone without visible perforation and or tearing can develop into a surgical ciliated cyst. Second, there is a possibility that covering the lateral window tightly might prevent the development of a surgical ciliated cyst.