Toyohiro Kagawa

Assessment of the Relationship Between Impacted Mandibular Third Molars and Inferior Alveolar Nerve With Dental 3-Dimensional Computed Tomography

PURPOSE The purpose of this study was to assess the capacity of dental 3-dimensional computed tomography (3D-CT; limited cone-beam CT) to predict the exposure and injury of the inferior alveolar nerve (IAN) after mandibular third molar extractions. MATERIALS AND METHODS This study was a retrospective case series of patients who presented for extraction of mandibular third molars. Subjects eligible for study enrollment were those who underwent preoperative dental 3D-CT because the mandibular third molars were determined to be extremely close to the IAN on panoramic radiogram. The predictive variable was the anatomic relation of the IAN and third molar apices and was a binary variable, contact or noncontact. The primary outcome variable was IAN exposure, and the secondary outcome variable was IAN injury. RESULTS From January 2006 to August 2007, 1,853 mandibular third molars in 1,539 patients were extracted. Among them, dental 3D-CT was performed on 53 third molars in 47 patients. The mandibular third molars were judged to make contact with the mandibular canal on dental 3D-CT images in 35 cases (66%). Intraoperative IAN exposure was observed in 17 (49%) contact cases and 2 (11%) noncontact cases on dental 3D-CT images. Of 53 cases extracted after dental 3D-CT examinations, IAN injury occurred in 8 cases (15%). IAN exposure led to IAN injury in 36.8% of cases, whereas IAN injury occurred in only 2.9% of cases without IAN exposure. Although the incidence of IAN injury in the molar-canal contact cases was 23%, all 8 cases with IAN injury (100%) were included in these contact cases. CONCLUSION When viewing the anatomic relation between the IAN and mandibular third molar root apices using dental 3D-CT, contact of the 2 anatomic structures results in an increased risk for IAN exposure or injury.

Cervical lymph nodes with or without metastases from oral squamous carcinoma: a correlation of MRI findings and histopathologic architecture.

OBJECTIVES The aim of this study was to describe the magnetic resonance images (MRIs) of the architecture of metastatic lymph nodes as well as healthy lymph nodes and to correlate the images with the histopathologic architecture of the lymph nodes from oral squamous cell carcinoma. STUDY DESIGN The signal intensities of 98 cervical lymph nodes from 20 patients with oral squamous cell carcinoma were evaluated on T2-weighted and diffusion-weighted whole-body imaging with background body signal suppression (DWIBS). The MRI findings were compared with the histopathologic architecture. RESULTS On T2-weighted images, very hyperintense and/or isointense areas were specific findings for lymph nodes containing metastases from oral squamous cell carcinoma. Histopathology indicated that these areas corresponded to cystic degeneration or keratinization. Using DWIBS images with inverted black-and-white image contrast, cystic degeneration, keratinization, fibrous tissue, tumor tissue, and lymphoid tissue were either hypointense or intermediate in intensity. CONCLUSIONS On T2-weighted images, very hyperintense and/or isointense areas were characteristic findings for lymph nodes containing metastases from oral squamous cell carcinoma. This suggests cystic degeneration or keratinization within the affected lymph nodes. Using DWIBS images, it was difficult to differentiate metastatic from benign lymph nodes.

Development of a simple image viewer designed for small X-ray field CT equipment 3DX

ObjectivesTo develop a simple image viewer that utilizes image files in general-purpose formats that are written from the original 3DX volume data.MethodsWe used FLASH MX2004 for Macintosh to develop a simple image viewer. In developing the software for the simple image viewer, we decided that the viewer should provide the following features: (1) be available to both Windows OS and Mac OS, (2) allow interlocking of the 3D images, (3) display image enlargement, and (4) allow distance measurements. The accuracy of the distance measurements was evaluated.ResultsThe procedure was as follows: (1) write 3D images in jpeg format to a folder on i-VIEW; (2) place the folder containing the 3D images into the directory of the simple image viewer software on a PC; (3) start the software and open the window to input the folder name containing the 3D images; and (4) display the 3D images. Our viewer had features such as image enlargement, interlocking 3D images, drawing, and distance measurements. No significant differences were shown between the measurements made by our simple viewer and the actual values of the images in any direction.ConclusionsOur image-viewing software for 3DX is beneficial for clinical use.

Evaluation of diffusion parameters and T2 values of the masseter muscle during jaw opening, clenching, and rest

Background Diffusion-weighted imaging (DWI) and diffusion-tensor imaging (DTI) can be used to evaluate changes that accompany skeletal muscle contraction. Purpose To investigate whether jaw opening or closure affect the diffusion parameters of the masseter muscles (MMs). Material and Methods Eleven healthy volunteers were evaluated. Diffusion-tensor images were acquired to obtain the primary (λ1), secondary (λ2), and tertiary eigenvalues (λ3). We estimated these parameters at three different locations: at the level of the mandibular notch for the superior site, the level of the mandibular foramen for the middle site, and the root apex of the mandibular molars for the inferior site. Results Both λ2 and λ3 during jaw opening were significantly lower than that at rest at the superior (P = 0.006, P < 0.0001, respectively) and middle site (P = 0.004, P = 0.0001, respectively); however, the change in λ1 was not significant. At the lower site, no parameter was significantly different at rest and during jaw opening. There was no significant difference in T2 between at rest (40.3 ± 4.4 ms) and during jaw opening (39.2 ± 2.7 ms; P = 0.12). The changes induced by jaw closure were marked at the inferior site. In the middle and inferior sites, the three eigenvalues were increased by jaw closure, and the changes in λ1 (P = 0.0145, P = 0.0107, respectively) and λ2 (P = 0.0003, P = 0.0001) were significant (especially λ2). Conclusion The eigenvalues for diffusion of the MM were sensitive to jaw position. The recruitment of muscle fibers, specific to jaw position, reflects the differences in changes in muscle diffusion parameters.

Dynamic magnetic resonance imaging of cervical lymph nodes in patients with oral cancer: utility of the small region of interest method in evaluating the architecture of cervical lymph nodes

ObjectiveOur purpose was to evaluate the utility of the small region of interest (ROI) method to detect the architecture of cervical lymph nodes and the specificity of time-intensity curves for tissue present in cervical lymph nodes.MethodsSpecimens were taken from 17 lymph nodes of eight patients (ten sides of the neck) with oral squamous cell carcinoma who underwent dynamic contrast-enhanced magnetic resonance imaging (MRI) and neck dissection between 2005 and 2007 at our hospital. Two methods of constructing time-intensity curves were compared: the conventional method that uses relatively large ROIs, and a new method that uses small ROIs. Curves made with the small ROI method were then compared to histopathological findings for dissected lymph nodes.ResultsThe small ROI method allowed differences in signal intensity to be discerned at the tissue level, which was not possible with the conventional large ROI method. Curves for normal lymphoid tissue tended to be type I, those for tumor cells tended to be type II, and those for keratinization/necrosis tended to be types III and IV, indicating that time-intensity curves can be specific to tissue type within lymph nodes.ConclusionThe small ROI method was useful for evaluation of the architecture of cervical lymph nodes.

Double Mandibular Canals : Report of a case

We report a forensic case in which bilateral double mental foramina with double mandibular foramina, and double mandibular canals on the left side of the lower jaw were noted in the bleached white skull of an unidentified Japanese male of the estimated age of 50 years.

Basic principles of magnetic resonance imaging for beginner oral and maxillofacial radiologists

The basic principles and diagnostic methods of magnetic resonance imaging (MRI) for beginning surgeons are described in this review. MRI is an important technique that is essential for diagnoses in the maxillofacial area. It is a scanning method that obtains tomographic images of the human body using a magnetic field. In contrast to computed tomography, it does not utilize X-rays and, therefore, represents a noninvasive test that lacks radiation exposure. It is particularly effective for soft-tissue diagnoses. MRI involves imaging protons in vivo. Protons emit a signal when a radio frequency pulse is applied in a magnetic field; the MRI device then forms an image from these signals. The basic images produced are T1- and T2-weighted images; comparison of these images is the first step of MRI-based diagnosis. Short-T1 inversion recovery images, which eliminate the signal from fat, are also useful for diagnosis. Gadolinium is used as a contrast agent for MRI. Taking sequential images at fixed intervals while injecting the contrast agent and then graphing the contrast effect along the time axis produces a time–signal intensity curve, which is useful for identifying features such as malignant neoplasms based on the graph pattern.

Computed tomography (CT) of cervical lymph nodes in patients with oral cancer: comparison of low-attenuation areas in lymph nodes on CT images with pathological findings

ObjectivesTo clarify the histopathological features of low-attenuation areas in computed tomography (CT) images of cervical metastatic and benign lymph nodes in patients with oral squamous cell carcinoma (SCC).MethodsCT images of 230 lymph nodes from 37 patients with oral SCC were classified into four categories and compared with histopathological findings. Metastatic lymph nodes were evaluated in terms of focal necrosis, keratinization, fibrous tissue, and the proportion of the lymph node showing focal necrosis. Benign lymph nodes were evaluated in terms of adipose tissue, follicular hyperplasia, sinus histiocytosis, hyperemia, focal hemorrhaging, and the amount of adipose tissue.ResultsHistopathologically, all 13 metastatic lymph nodes with rim enhancement on CT images included focal necrosis. However, most of the lymph nodes showed no focal necrosis. In addition, tumor cells, keratinization, and fibrous tissue were observed in the lymph nodes. Of the 26 metastatic lymph nodes with a heterogeneous appearance on CT images, four did not show focal necrosis. These lymph nodes showed keratinization or accumulation of lymph fluid. Histopathologically, 20 of 24 benign lymph nodes with a heterogeneous appearance on CT images (83.3%) had accompanying adipose tissue.ConclusionsFocal necrosis was the most important factor contributing to low attenuation in metastatic lymph nodes. However, other factors, such as tumor cells, keratinization, fibrous tissue, and accumulation of lymph fluid, also contributed. In benign lymph nodes, the presence of adipose tissue was a contributing factor in low-attenuation areas, as was focal hemorrhaging.