Jun Ichi Asaumi

Minor salivary gland tumors in the oral cavity: Diagnostic value of dynamic contrast-enhanced MRI

OBJECTIVEnTo evaluate the diagnostic value of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) for minor salivary gland tumors in the oral cavity.nnnMATERIALS AND METHODSnThirty-two patients with minor salivary gland tumors were examined preoperatively using DCE-MRI. Their maximum contrast index (CImax), time of CImax (Tmax), Tpeak; i.e., the time that corresponded to the CImax×0.90, and washout ratios (WR300 and WR600) were determined from contrast index (CI) curves. We compared these parameters between benign and malignant tumors and among the different histopathological types of minor salivary gland tumors. Then, we categorized the patients CI curves into four patterns (gradual increase, rapid increase with high washout ratio, rapid increase with low washout, and flat).nnnRESULTSnStatistically significant differences in Tmax (P=0.004) and Tpeak (P=0.002) were observed between the benign and malignant tumors. Regarding each histopathological tumor type, significant differences in Tmax (P<0.001), Tpeak (P<0.001), and WR600 (P=0.026) were observed between the pleomorphic adenomas and mucoepidermoid carcinomas. It was difficult to distinguish between benign and malignant tumors using our CI curve classification because that two-thirds of the cases were classified into the same type (gradual increase).nnnCONCLUSIONnThe DCE-MRI parameters of minor salivary gland tumors contributed little to their differential diagnosis compared with those for major salivary gland tumors. During the diagnosis of minor salivary gland tumors, Tmax is useful for distinguishing between benign and malignant tumors.

Diagnostic value of MRI for odontogenic tumours

OBJECTIVESnTo evaluate the diagnostic value of MRI for odontogenic tumours.nnnMATERIALS AND METHODSn51 patients with odontogenic tumours were subjected to pre-operative MRI examinations. For tumours with liquid components, i.e. ameloblastomas and keratocystic odontogenic tumours (KCOTs), the signal intensity (SI) uniformity of their cystic components (UΣ) was calculated and then their UΣ values were compared. For tumours with solid components that had been examined using dynamic contrast-enhanced MRI (DCE-MRI), their CImax (maximum contrast index), Tmax (the time when CImax occurred), CIpeak (CImaxu2009×u20090.90), Tpeak (the time when CIpeak occurred) and CI300 (i.e. the CI observed at 300u2009s after contrast medium injection) values were determined from CI curves. We then classified the odontogenic tumours according to their DCE-MRI parameters.nnnRESULTSnSignificant differences between the UΣ values of the ameloblastomas and KCOT were observed on T1 weighted images, T2 weighted images and short TI inversion recovery images. Depending on their DCE-MRI parameters, we classified the odontogenic tumours into the following five types: Type A, CIpeaku2009>u20092.0 and Tpeaku2009<u2009200u2009s; Type B, CIpeaku2009<u20092.0 and Tpeaku2009<u2009200u2009s; Type C, CI300u2009>u20092.0 and Tmaxu2009<u2009600u2009s; Type D, CI300u2009>u20092.0 and Tmaxu2009>u2009600u2009s; Type E, CI300u2009<u20092.0 and Tmaxu2009>u2009600u2009s.nnnCONCLUSIONnCystic component SI uniformity was found to be useful for differentiating between ameloblastomas and KCOT. However, the DCE-MRI parameters of odontogenic tumours, except for odontogenic fibromas and odontogenic myxomas, contributed little to their differential diagnosis.

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

INTRODUCTIONnIt 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.nnnMATERIALS AND METHODSnTen 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.nnnRESULTSnIn 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.nnnCONCLUSIONnMRI, 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.

Manifestation of preferred chewing side for hard food on TMJ disc displacement side

The purpose of this study was to reveal the relationship between chewing-side preference and anterior disc displacement (ADD) of the TMJ. Thirty-two healthy subjects with ages ranging from 26 to 34 years were selected from volunteer students at the Okayama University Dental School. Subjects were asked to chew freely with two kinds of test foods, beef jerky (hard food) and chiffon cake (soft food), thus expecting different amounts of mechanical loading on the TMJ. One, 4, and 7 s after starting the mastication, subjects were asked to open their mouth momentarily to have a digital image of their mouth taken. The bolus placement area was measured by processing the digital images, calculated as the number of pixel of bolus area. Area asymmetry index was used for the determination of preferred chewing side (PCS). Oblique sagittal MRI scanning in the closed mouth position was taken to evaluate the articular disc position. In asymptomatic subjects with ADD, a significant predominance of the PCS on the ipsilateral side of ADD was observed during the mastication of hard food. On the contrary, no correlation was found between unilateral ADD and PCS for the soft food. From the results of this study, it is suggested that ADD is the associating factor of PCS for hard food. Therefore, it would be necessary to break down the concept of PCS into at least two categories, one for hard food and one for soft food, considering the mechanical loading on the TMJ.

Ameloblastic carcinoma: a case report with radiological features of computed tomography and magnetic resonance imaging and positron emission tomography.

Ameloblastic carcinoma is a rare malignant odontogenic carcinoma that has metastatic potential, and because of its rare incidence, there are few reports focusing on its radiologic imaging. If it shows aggressive appearances, it can be diagnosed as malignant tumor. But in case of negative appearance, it is difficult to distinguish ameloblastic carcinoma from ameloblastoma. We report a case of ameloblastic carcinoma of the maxilla in a 76-year-old female patient with radiologic images and pathologic features.

Solid-type primary intraosseous squamous cell carcinoma of the mandible: a case report with histopathological and imaging features

Primary intraosseous squamous cell carcinoma (PIOSCC) is a rare malignant odontogenic tumor arising from odontogenic epithelial remnants within the jawbones. PIOSCC is histopathologically divided into 3 types: solid-type carcinoma, carcinoma derived from a keratocystic odontogenic tumor, and carcinoma derived from an odontogenic cyst. In this article, we report a case of solid-type PIOSCC involving reactive bone formation in the mandible in a 60-year-old female patient together with its histopathological and imaging findings.

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

OBJECTIVEnThe 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.nnnSTUDY DESIGNnThirteen 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.nnnRESULTSnThe 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%.nnnCONCLUSIONSnThe 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

OBJECTIVESnTo evaluate the diagnostic value of dynamic contrast-enhanced MRI (DCE-MRI) for differentiating between benign and malignant tumors in the palate.nnnMATERIALS AND METHODSn26 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.nnnRESULTSnIn 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).nnnCONCLUSIONSnTmax is a useful parameter for distinguishing between benign and malignant submucosal palatal tumors.

Central odontogenic fibroma of the jawbone: 2 case reports describing its imaging features and an analysis of its DCE-MRI findings

Odontogenic fibroma (OF) is a rare nonepithelial benign tumor arising from the odontogenic mesenchymal tissue in the jawbone. OFs are topographically categorized into 2 types, the central type and peripheral type, and are histopathologically divided into the epithelium-poor type and epithelium-rich type. The radiological findings of central OF commonly include a uni- or multilocular radiolucent area with a well-defined margin, which are similar to those of cysts and other benign tumors of the jawbone. Therefore, it is difficult to distinguish OF from these jawbone lesions on radiographs because of their noncharacteristic radiological findings. In this article, we report the cases of 2 patients with central OF who underwent magnetic resonance (MR) examinations and describe the usefulness of dynamic contrast-enhanced MR imaging for diagnosing OF.