Skip global navigation and read the article

Skip global navigation and go to local navigation

Skip global navigation and go to footer navigation



Home  > Oral and Maxillofacial Radiology  > Research Subjects

Research Subjects

Although our research projects cover a variety of topics within a scope of radiological science, the strength of our section is mainly in diagnostic imaging, and radiation oncology. The followings are some representatives of our recent research results.


1. Trigeminal Neuralgia: evaluation of neuralgic manifestation and site of neurovascular compression with 3D CISS MR imaging and MR angiography (Yoshino N et al. Radiology 2003; 228: 539-545)

Abstract
PURPOSE: To evaluate three-dimensional (3D) constructive interference in steady-state (CISS) magnetic resonance (MR) imaging and MR angiography with multiplanar reconstruction (MPR) for detection of neurovascular compression (NVC) in patients with trigeminal neuralgia and to evaluate the relationship between clinical symptoms related to trigeminal branches and those related to the site of trigeminal nerve compression.
MATERIALS AND METHODS: Fifty-four consecutive patients with trigeminal neuralgia were examined at 3D CISS imaging and MR angiography with a 1.5-T MR system. Original transverse and four reformatted images were used for image interpretation. Vascular contact with the trigeminal nerve at the root entry zone (REZ) was determined, and the nature of the involved vessels was identified. The position of the blood vessel compressing the nerve was classified into cranial, caudal, medial, or lateral sites. Statistical analysis was performed with the x2 test or the Fisher exact test between two groups and with the x2 test among more than two groups.
RESULTS: In 12 of 15 patients who underwent surgery, the artery that was considered a responsible vessel at 3D CISS imaging and MR angiography was confirmed as such. In the other three patients, the vein was the responsible vessel, which was detected only at 3D CISS imaging. Sixteen (89%) of 18 patients with symptoms related to the maxillary division had NVC at the medial site of the REZ, while 16 (76%) of 21 patients with symptoms related to the mandibular division had NVC at the lateral site (P < .001, x2 test).
CONCLUSION: 3D CISS MR imaging with MPR is useful in the detection of NVC in patients with trigeminal neuralgia, compared with MR angiography. A close relationship was found between the region of neuralgic manifestation and the site of trigeminal nerve compression.

2. Inhibition of the Extracellular Signal-regulated Kinase (ERK) Pathway Induces Radioresistance in Rat 3Y1 Cells. (Watanabe H et al. Int. J. Radiat. Biol. 2004; 80: 451-457)

Abstract
Purpose: Activation of the extracellular signal-regulated kinase (ERK) pathway generally results in stimulation of cell growth and confers a survival advantage. However, the potential involvement of this pathway in cellular radiosensitivity remains unclear. This study was designed to examine whether the ERK pathway affects intrinsic radiosensitivity in mammalian cells.
Materials and methods: Exponentially growing rat 3Y1 cells were used in this study. A specific inhibitor of mitogen-activated ERK kinase (MEK), PD98059, was utilized to inhibit the ERK pathway. In addition, kinase-deficient MEK was expressed in cells to inhibit the pathway in a dominant negative manner. Activation of ERK was visualized by Western blot using an antibody which recognizes the phosphorylated form of ERK. Radiosensitivity was evaluated by colony-forming assay.
Results: 3Y1 cells treated with PD98059 exhibited a significant inhibition of cell proliferation and radiation-induced transient activation of ERK. Unexpectedly, we found that the inhibitor enhanced clonogenic radioresistance in a dose-dependent manner. This effect on radioresistance was confirmed by expression of kinase-deficient MEK.
Conclusion: We conclude that activation of the MEK/ERK pathway increases clonogenic radiosensitivity in rat 3Y1 cells. These findings, together with a variety of other data, suggest that there may be clinical implications in targeting the MEK/ERK pathway in radiotherapy.

3. Evidence that Basal Activity, But Not Transacrivation, of the Epidermal Growth Factor Receptor Tyrosine Kinase Is Required for Insulin-like Growth Factor I-Induced Activation of Extracellular Signal-Regulated Kinase in Oral Carcinoma Cells. (Kuribayashi A et al. Endocrinology 2004; 145: 4976-4984)

Abstract
Insulin-like growth factor I receptor (IGF-IR) is involved in numerous biological functions via its major downstream signaling molecules, extracellular signal-regulated kinase (ERK) and phospohatidylinositol-3’ kinase (PI3-K)/Akt. The IGF-I-induced activation of ERK, but not that of Akt, is reportedly mediated by the transactivation of the epidermal growth factor receptor (EGFR) tyrosine kinase (TK). The mechanism for the EGFR-TK-dependent activation, however, still remains largely unknown. We found that an oral carcinoma cell line overexpressing EGFR, Ca9-22, exhibited IGF-I-induced activation of both Akt and ERK, but that only the latter was significantly decreased by a specific inhibitor of EGFR-TK, tyrphostin AG1478. In this report, we provide evidence for the existence in this cell line of a novel mechanism by which IGF-I induces ERK activation in a manner that is dependent on the basal level of EGFR-TK activity, but is independent of receptor transactivation. In addition, we show that c-Raf kinase is likely to be a key regulator of this mechanism. The elucidation of such a unique mechanism involving cross-talk between EGFR and heterologous receptors may shed additional light on the clinical use of EGFR-TK inhibitors in anti-tumor therapies.

4. CT findings as a significant predictive factor for the curability of mandibular osteomyelitis: multivariate analysis (Ida M et al. Dentomaxillofacial Radiol 2005; 34: 86-90)

Abstract
Objectives: To reevaluate computed tomographic imaging as a diagnostic tool for mandibular osteomyelitis and to assess the clinical significance of CT findings.
Methods: CT images of 78 patients with mandibular osteomyelitis were reviewed. All patients were classified as cured or non-cured. Each CT finding was investigated for frequency, correlation with duration, and disease cure.
Results: Of the 78 patients, 49 (63%) were classified as “cured” and 29 (37%) as non-cured. Non-cured had experienced a significantly longer duration of symptoms. The most frequent CT finding was sclerosis and defect in the trabecular bone. The changes of bone width and thickening of the cortical plate were accompanied with longer disease duration. The extent of the diseased area was linearly correlated with the duration of symptoms. The significant factors to discriminate non-cured from cured were the extent of the disease, the number of findings, changes in the bone width, osteosclerosis and thickening of the cortex. Multivariate logistic regression analysis indicated that the extent of the disease and presence of changes in bone width were significant variables correlating with the cure of osteomyelitis.
Conclusions: The extent of disease and the presence of change in bone width shown on CT were significantly correlated with the curability of osteomyelitis. These results indicated the usefulness and importance of CT examination for the diagnosis of mandibular osteomyelitis.

5. A Potential Pitfall of MR Imaging for Assessing Mandibular Invasion of Squamous Cell Carcinoma in the Oral Cavity (Imaiuzmi A et al. AJNR Am J Neuroradiol 2006; 27: 114-122)

Abstract

BACKGROUND AND PURPOSE: Whether MR imaging is superior to CT in evaluating the presence and extent of mandibular invasion by squamous cell carcinoma remains controversial. The purpose of this study was to directly compare the diagnostic accuracy of MR imaging and that of CT.
METHODS: MR and CT images in 51 patients with squamous cell carcinoma of the oral cavity were evaluated for the presence and extent of mandibular invasion. The results were correlated with histopathologic findings.
RESULTS: Twenty-five of 51 patients had histopathologic evidence of mandibular cortical invasion. The tumor involved both the cortex and the bone marrow in all 25 patients and involved the inferior alveolar canal in 5 patients. The sensitivity and specificity for mandibular cortical invasion were 96% and 54% for MR imaging and 100% and 88% for CT, respectively. Those for inferior alveolar canal involvement were 100% and 70% for MR imaging and 100% and 96% for CT, respectively. In both evaluations, the specificity of MR imaging was significantly lower than that of CT (McNemar test, P = .004 in the former and P = .002 in the latter). Chemical shift artifact by bone marrow fat was postulated to be the source of most false-positive cases on MR imaging findings for mandibular cortical invasion. Those for inferior alveolar canal involvement were due to MR imaging visualization of the tumor and surrounding inflammation with similar signal intensity.
CONCLUSION: In assessing the presence and extent of mandibular invasion by squamous cell carcinoma, the specificity of MR imaging was significantly lower than that of CT.

6. A comparative study of cone-beam computed tomography and conventional panoramic radiography in assessing the topographic relationship between the mandibular canal and impacted third molars (Tantanapornkul W et al. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2007; 103: 253-259)

Abstract

Objective: To evaluate the diagnostic accuracy of cone-beam CT in predicting neurovascular bundle exposure following impacted mandibular third molar extraction and to compare it with that of panoramic images.
Study design: Cone-beam CT and panoramic features of 142 impacted mandibular third molars were prospectively evaluated as to the topographic relationship with mandibular canal. These findings were then correlated with intraoperative findings. The sensitivity and specificity of the two modalities in predicting neurovascular bundle exposure at extraction were calculated and compared. The diagnostic criterion for panoramic images was defined using multivariate logistic regression analysis.
Results: In predicting the exposure, the sensitivity and specificity were 93% and 77% for cone-beam CT, and 70% and 63% for panoramic images, respectively, showing that cone-beam CT was significantly superior to panoramic images in both respects.
Conclusion: Cone-beam CT was significantly superior to panoramic images in predicting neurovascular bundle exposure following impacted mandibular third molar extraction.

7. MRI and clinical findings of posterior disk displacement in the temporomandibular joint (Okochi K et al. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008; 105: 644-648)

Abstract

Objective: To evaluate the magnetic resonance imaging and clinical findings of patients with posterior disk displacement in the temporomandibular joint.
Study design: Magnetic resonance and clinical findings of 62 temporomandibular joints (44 patients) with posterior disk displacement were retrospectively analyzed.
Results: According to the criteria proposed by Westesson et al., 52 temporomandibular joints (84%) were the thin flat disk type and the remaining ten(16%) were the perforated disk type. Fifteen temporomandibular joints (24%) had a history of luxation. Clicking was observed in 26 temporomandibular joints (42%), all of which were the thin flat disk type (chi-square test, P< 0.01). Pain was observed in 19% of patients with the thin flat disk type and 60% of those with the perforated disk type (P< 0.05).
Conclusions: Magnetic resonance imaging could clearly reveal the details of posterior disk displacement in the temporomandibular joint. The clinical findings were dissimilar between the thin flat and the perforated disk type.

8. Prediction of Lymphatic Metastasis Based on Gene Expression Profile Analysis after Brachytherapy for Early-Stage Oral Tongue Carcinoma (Watanabe H et al. Radiother Oncol 2008; 87: 237-242)

Abstract

Background and purpose: The management of lymphatic metastasis of early-stage oral tongue carcinoma patients is crucial for its prognosis. The purpose of this study was to evaluate the predictive ability of lymphatic metastasis after brachytherapy (BRT) for early-stage tongue carcinoma based on gene expression profiling.
Patients and methods: Pre-therapeutic biopsies from 39 patients with T1 or T2 tongue cancer were analyzed for gene expression signatures using Codelink Uniset Human 20K Bioarray. All patients were treated with low dose-rate BRT for their primary lesions and underwent strict follow-up under a wait-and-see policy for cervical lymphatic metastasis. Candidate genes were selected for predicting lymph-node status in the reference group by the permutation test. Predictive accuracy was further evaluated by the prediction strength (PS) scoring system using an independent validation group.
Results: We selected a set of 19 genes whose expression differed significantly between classes with or without lymphatic metastasis in the reference group. The lymph node status in the validation group was predicted by the PS scoring system with an accuracy of 76%.
Conclusions: Gene expression profiling using 19 genes in primary tumor tissues may allow prediction of lymphatic metastasis after BRT for early-stage oral tongue carcinoma.

9. An investigation of magnetic resonance imaging features in 14 patients with synovial chondromatosis of the temporomandibular joint. (Ida M et al. Dentomaxillofac Radiol 2008; 37: 213-219)

Abstract

Objectives: To show the characteristic magnetic resonance imaging (MRI) features of synovial chondromatosis (SC) of the temporomandibular joint (TMJ).
Methods and Materials: All patients with histologically proven SC of the TMJ who underwent MRI at our clinic were examined. In 14 patients (male:female=2:12, average age=46±14 years), clinical and conventional radiographic findings were reviewed. In addition, MRI findings of articular disc and condyle position, shape and signal intensity of the joint spaces, and bone changes of surrounding structures were analyzed.
Results: The main symptoms were pain (93% of the patients) and limitation of mouth opening (64%). Two cases showed typical multiple calcifications around TMJ on conventional radiography. On MRI, disc position was normal in 12 patients (86%) and the condyle was inferiorly displaced in 9 patients (64%). Eleven patients (79%) showed enlargement of the joint space, either a “dumbbell” shape or bulging. SC in the upper compartment showed various degrees of bone changes of articular eminence and fossa. SC in the lower compartment showed concavity or hypertrophy of the condyle. The severity of the bone changes progressed with duration of symptoms.
Conclusions: About 0.3% of the patients complaining of TMJ pain and dysfunction were found to have SC. There was great variation in the MRI features of the TMJs with SC. More severe destruction of surrounding bone structures with features resembling a tumor were found in patients with a longer duration of symptoms.

10. MRI findings of temporomandibular joints with disk perforation (Kuribayashi A et al. Oral Surg Oral Med Oral Pat Oral Radiol 2008; 106: 419-425)

Abstract

Objective: To investigate MRI findings of TMJs with disk perforation.
Study Design: Thirty-one TMJs (31 patients) with disk perforation, 37 TMJs (34 patients) with anterior disk displacement and no disk perforation and 22 asymptomatic TMJs of 11 volunteers were examined by MRI. The presence or absence of disk perforation was confirmed by TMJ arthrography. MR images were evaluated for the presence or absence of disk deformity, disk displacement, condylar bone changes and joint effusion, and for visualization of the temporal posterior attachment (TPA) of the posterior disk attachment. Those findings were compared among the three groups.
Results: The incidences of anterior disk displacement and condylar bone changes in the patients group with disk perforation were significantly higher than in asymptomatic volunteers. Disk deformity and obscurity of TPA were significantly more frequent in the patient group with disk perforation than in the other two groups.
Conclusion: In addition to disk deformity, TPA obscurity was considered one of the characteristic MRI findings of TMJs with disk perforation.

11. Correlation of darkening of impacted mandibular third molar root on digital panoramic images with cone-beam computed tomography findings. (Tantanapornkul W et al. Dentomaxillofac Radiol 2009; 38: 11-16)

Abstract

Objectives: Darkening of the lower third molar root on panoramic images is known to indicate an intimate relationship between the root and mandibular canal. The objective of this study was to investigate the anatomical relationship between the third molar root and its surrounding structures that leads to this panoramic finding.
Methods: Imaging findings of 253 impacted lower third molars examined by both digital panoramic radiography and cone beam CT were reviewed. Panoramic images were evaluated to detect the presence or absence of darkening of the root where the mandibular canal was superimposed. Cone beam CT images were evaluated for the presence or absence of the following two findings: (1) grooving of the root and (2) thinning or perforation of the cortical plate by the root. The correlation between the panoramic and cone beam CT findings was examined using logistic regression analysis.
Results: 80 (32%) third molars showed a panoramic finding of darkening of the root. Between cone beam CT findings, cortical thinning or perforation alone was significantly correlated with this panoramic finding (80%, P , 0.001).
Conclusions: The panoramic finding of mandibular third molar root darkening was considered to reflect cortical thinning or perforation rather than grooving of the root.

12. Tissue characterization of head and neck lesions using diffusion- weighted MR imaging with SPLICE. (Sakamoto J et al. Eur J Radiol, in press)

Abstract

Purpose: The purpose of this study was to evaluate the usefulness of diffusion-weighted (DW) MR imaging with split acquisition of fast spin-echo signals (SPLICE) in the tissue characterization of head and neck mass lesions.
Patients and methods: DW MR images of 67 head and neck mass lesions were obtained using SPLICE with b-factors of 0 and 771 s/mm2. The lesions were classified into three categories: 16 cysts, 32 benign tumors, and 19 malignant tumors. After ADC maps were constructed for all lesions, ADC values were calculated and compared among the three categories.
Results: No case showed severe image distortion on DW MR imaging with SPLICE, and reliable ADC maps and ADC values were obtained in all cases. The mean ADC value of cysts was 2.41±0.48×10-3 mm2/s, which was significantly higher than that of benign (1.48±0.62×10-3 mm2/s) and malignant (1.23±0.45×10-3 mm2/s) tumors (P<0.001). However, there was no significant difference between the ADC values of benign and malignant tumors (P=0.246). When an ADC value of 2.10×10-3 mm2/s or higher was used as the diagnostic criterion for cysts, the sensitivity, specificity, and accuracy were 94%, 88%, and90%, respectively.
Conclusion: SPLICE was considered a recommended DW MR imaging technique for the head and neck. Although ADC values were useful in differentiating cysts from tumors, they contributed little in predicting malignancy.

13. Diagnostic accuracy of cone-beam CT in the assessment of mandibular invasion of lower gingival carcinoma: comparison with conventional panoramic radiography. (Momin MA et al. Eur J Radiol, in press)

Abstract

Purpose: To evaluate the diagnostic accuracy of cone-beam CT in assessing mandibular invasion by lower gingival carcinoma and compare it with that of panoramic radiography.
Patients and methods: Fifty patients with squamous cell carcinoma of the lower gingiva who were examined by both panoramic radiography and cone-beam CT before surgery were included in this study. Five radiologists used a 6-point rating scale to independently evaluate cone-beam CT and panoramic images for the presence or absence of alveolar bone and mandibular canal involvement by tumor. Using the histopathogical findings as the gold standard, we calculated and compared the area under the receiver operating characteristic curve (Az value) and the sensitivity and specificity of the two imaging modalities.
Results: In evaluations of both alveolar bone and mandibular canal involvement, the mean Az value for cone-beam CT (0.918and0.977, respectively) was significantly higher than that for panoramic radiography (0.793 and 0.872, respectively). The mean sensitivity for cone-beam CT (89% and 99%, respectively) was significantly higher than that for panoramic radiography (73% and 56%, respectively). There was no significant difference in the mean specificity. While cone-beam CT could provide high-resolution three-dimensional images, the image quality around the alveolar crest was often hampered by severe dental artifacts and image noise, resulting in difficulties in detecting subtle alveolar invasion.
Conclusion: Cone-beam CT was significantly superior to panoramic radiography in evaluating mandibular invasion by lower gingival carcinoma. Its diagnostic value in detecting subtle alveolar invasion, however, may be limited by severe dental artifacts and image noise.