Kiyoshi Okochi

Correlation of darkening of impacted mandibular third molar root on digital panoramic images with cone beam computed tomography findings

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.

Diagnostic performance of magnetic resonance imaging for detecting osseous abnormalities of the temporomandibular joint and its correlation with cone beam computed tomography

OBJECTIVE With cone beam CT (CBCT) as the reference standard, the objective of this study was to determine the diagnostic accuracy of MRI for assessing osseous abnormalities of the temporomandibular joint (TMJ). METHODS 106 TMJs from 55 patients with temporomandibular disorder were examined by CBCT and MRI. CBCT images were evaluated by two experienced oral radiologists with regard to the presence or absence of each of the following eight types of osseous abnormalities: Type 1, destructive and erosive osseous changes of the condyle; Type 2, flattening of the articular surface of the condyle; Type 3, deformity of the condyle; Type 4, sclerosis of the condyle; Type 5, osteophyte formation; Type 6, ankylosis; Type 7, erosion of the articular fossa and/or eminence; and Type 8, sclerosis of the articular fossa and/or eminence. For detection of these osseous abnormalities by MRI, proton density-weighted images and T(2) weighted images were evaluated independently by three observers. Using CBCT findings as the reference standard, the diagnostic performance of MRI for detecting various types of osseous abnormalities was evaluated by calculating its sensitivity and specificity. RESULTS Out of 106 joints, CBCT revealed Types 1, 2, 3, 4, 5, 6, 7 and 8 abnormalities in 25, 19, 26, 20, 14, 5, 19 and 22 joints, respectively. The mean sensitivities of MRI among the three observers for detecting Types 1, 2, 3, 4, 5, 6, 7 and 8 abnormalities were 61%, 30%, 82%, 40%, 48%, 34%, 61% and 41%, respectively, whereas the mean specificities were 86%, 92%, 91%, 95%, 84%, 98%, 89% and 91%, respectively. CONCLUSIONS Although high specificity (84-98%) was obtained with MRI, this modality showed relatively low sensitivity (30-82%) for detecting osseous abnormalities of the TMJ. The value of MRI for the detection of TMJ osseous abnormalities is considered to be limited.

Diagnostic accuracy of cone-beam CT in the assessment of mandibular invasion of lower gingival carcinoma: Comparison with conventional panoramic radiography

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 (0.918 and 0.977, 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.

Biological Response to Ionizing Radiation in Mouse Embryo Fibroblasts with a Targeted Disruption of the DNA Polymerase β Gene

Abstract Miura, M., Watanabe, H., Okochi, K., Sasaki, T. and Shibuya, H. Biological Response to Ionizing Radiation in Mouse Embryo Fibroblasts with a Targeted Disruption of the DNA Polymerase β Gene. Base excision repair (BER) is carried out by two distinct pathways in mammalian cells, one dependent on DNA polymerase β (Polb) and the other on proliferating cell nuclear antigen (Pcna). We studied whether the Polb-dependent pathway plays an important role in BER in vivo after exposure to ionizing radiation. For this purpose, we used mouse embryo fibroblasts derived from wild-type and Polb gene knockout littermates. Both cell lines had essentially the same clonogenic cell survival and low levels of apoptosis as determined by a colony formation assay and by a change in mitochondrial membrane potential, respectively. No significant cleavage of protein kinase C δ (Pkcd) in vivo, which is a substrate for caspase 3, was detected, and intact Pkcd was retained in both cell lines for at least 72 h after irradiation. Similar significant increases in caspase 3-like activities as measured by Asp-Glu-Val-Asp (DEVD) cleaving activity in vitro were observed in both cell lines after irradiation. Radiation induced cell cycle arrest in the form of a G2-phase block, and G2/M-phase fractions reached a peak approximately 10 h after irradiation and decreased thereafter with a similar time course in both cell lines. Similar levels of chromatin-bound Pcna were observed immediately after irradiation in non-S-phase cells of both cell lines and disappeared by 4 h after irradiation. We conclude that the deficiency in Polb does not have a significant influence on the radiation responses of these cells. Together with evidence accumulated in vitro, these results strongly support the idea that the Pcna-dependent pathway predominantly acts in BER of radiation-induced DNA damage in vivo.

[18F]Fluorodeoxyglucose-PET/CT differentiation between physiological and pathological accumulations in head and neck.

ObjectivesThe purposes of this study were to evaluate various physiological fluorodeoxyglucose (FDG) accumulations in the head and neck and to compare those with tumor (pathological) FDG accumulation. MethodsOne hundred and twelve patients with head and neck carcinomas were studied. PET/computed tomography examinations were performed 1 h after intravenous injection of fluorine-18-labeled FDG. The tumor and the physiological FDG accumulations were identified with PET/computed tomography images, and the maximum of the standardized uptake value (SUVmax) was calculated. ResultsPhysiological FDG accumulation was observed in tonsil, extraocular muscle, masticatory muscle, vocal cord, and the major salivary glands: parotid, submandibular, and sublingual gland. The accumulation in tonsil, extraocular muscle, and sublingual gland showed relatively high SUVmax. The tumor FDG accumulation was significantly higher than any physiological FDG accumulation. The optimal cut-off values of SUVmax for differentiating physiological FDG accumulation from pathological FDG accumulation were 4.0 for parotid gland, 4.5 for submandibular gland, 5.5 for sublingual gland, 8.0 for tonsil, and 10.0 for extraocular muscle. The right-to-left ratio of SUVmax was less than 1.5 in any physiological accumulation. ConclusionTonsil, extraocular muscle, and sublingual gland showed relatively high FDG accumulation, which was sometimes similar to tumor accumulation. The right-to-left ratio of SUVmax was considered useful in differentiating tumor from physiological accumulation, and the presence of tumor might be highly suspected in cases with a ratio of 1.5 or more.

MRI and clinical findings of posterior disk displacement in the temporomandibular joint

OBJECTIVE The objective of this study was 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 10 (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 < .01). Pain was observed in 19% of patients with the thin flat disk type and 60% of those with the perforated disk type (P < .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.

Can dual-time-point 18F-FDG PET/CT differentiate malignant salivary gland tumors from benign tumors?

OBJECTIVE The purpose of this study is to evaluate the usefulness of dual-time-point 18F-FDG PET/CT for discriminating between benign and malignant salivary gland tumors. MATERIALS AND METHODS Dual-time-point FDG PET/CT images of 40 salivary gland tumors (20 benign and 20 malignant) were evaluated retrospectively. The maximum standardized uptake values (SUVmax) in the early and delayed phases and the retention index of each tumor were calculated and compared between benign and malignant tumors by the Mann-Whitney U test. Receiver operating characteristic (ROC) analysis was used to determine the diagnostic accuracy for malignant salivary gland tumors. The correlation between the delayed SUVmax and retention index was analyzed by calculation of the Spearman correlation coefficient. RESULTS There were no significant differences in the mean early phase SUVmax or mean delayed phase SUVmax between benign and malignant tumors. The mean (±SD) retention index of the malignant tumors was significantly higher than that of the benign tumors (20.1%±10.2% vs 8.5%±12.3%; p=0.006). When the cutoff value of retention index (15.0%) was used, the sensitivity, specificity, and accuracy each was determined to be 75.0%. ROC analysis did not reveal a significant difference in the diagnostic accuracy between the delayed phase SUVmax and retention index (p=0.139). A significant correlation between the delayed phase SUVmax and retention index was observed for the benign salivary gland tumors (r=0.839; p<0.001). CONCLUSION Dual-time-point FDG PET/CT is not useful for discriminating between benign and malignant salivary gland tumors, because benign tumors also show high FDG uptake, which increases in the delayed phase.

MRI characteristics of rheumatoid arthritis in the temporomandibular joint.

OBJECTIVES The aim of this study was to investigate characteristic MRI findings of rheumatoid arthritis (RA) in the temporomandibular joints (TMJs). METHODS 61 patients (122 TMJs) with RA in the TMJ and 50 patients (100 TMJs) with temporomandibular disorder (TMD) were included in this study. MR images of these patients were assessed by two oral radiologists for the presence or absence of osseous changes, disc displacement, joint effusion and synovial proliferation. These findings were compared between the two patient groups. RESULTS Osseous changes in the condyle and articular eminence/fossa in the RA patient group were significantly more frequent than in the TMD patient group, and were often very severe. Joint effusion was also significantly more frequent in the RA patient group. Synovial proliferation was found in all TMJs in the RA patient group, whereas it was very uncommon in the TMD patient group. CONCLUSIONS Severe osseous changes in the condyle and synovial proliferation were considered characteristic MRI findings of RA in the TMJs.

Magnetic resonance imaging of temporomandibular joint cyst

OBJECTIVE The objective of this study was to evaluate the magnetic resonance imaging (MRI) and clinical findings of 6 cases with synovial or ganglion cysts occurring in the temporomandibular joint (TMJ). STUDY DESIGN Six patients with histopathologically confirmed TMJ cysts who were examined by MRI were included in this study. Two oral radiologists retrospectively evaluated MR images. RESULTS MR images revealed a homogeneous well defined mass of the TMJ in all cases. These cysts demonstrated low signal intensity on proton density-weighted (PDW) and homogeneous very high signal on T2-weighted (T2W) images. They were all characteristically continuous with the joint capsule. Regarding clinical features, all 6 patients had some type of TMJ pain. CONCLUSIONS TMJ cysts were identified as well defined homogeneous masses with low signal intensity on PDW and very high signal on T2W images, and characterized by continuity with the joint capsule. All of the patients with TMJ cysts exhibited some type TMJ pain.

Dual-time-point fluorodeoxyglucose positron emission tomography for diagnosis of cervical lymph node metastases in patients with head and neck squamous cell carcinoma.

Objective: The purpose of this study was to evaluate whether dual-time-point fluorodeoxyglucose positron emission tomography/computed tomography image can improve nodal diagnosis in patients with head and neck squamous cell carcinoma (HNSCC). Methods: One hundred six HNSCC patients were enrolled. Positron emission tomography/computed tomography images were obtained twice: 1 and 2 hours after fluorodeoxyglucose injection. Maximum standardized uptake value (SUVmax) and SUVmax increasing rate (SUV-IR) were compared with the histopathologic findings to determine the optimal cutoff for nodal diagnosis. Results: Using early-phase image, SUVmax ≧ 2.75 was considered as optimal criterion. When using delayed-phase, SUVmax ≧ 3.5 was optimal. There was no significant difference between these criteria. Maximum standardized uptake value IR ≧ 8.0 (10−3/s) was considered as optimal, although it provided relatively low sensitivity (66%) and specificity (82%). However, combined criterion of SUVmax ≧ 3.5 in delayed-phase or SUV-IR ≧ 8.0 (10−3/s) significantly improved the specificity (90%) and accuracy (89%) without decreasing the sensitivity (84%). Conclusions: Using delayed-phase image combined with SUV-IR can improve the nodal diagnosis in HNSCC patients.