Tsuyoshi Sawamura

Impacted teeth in the maxilla: usefulness of 3D Dental-CT for preoperative evaluation

OBJECTIVE To compare the shapes of roots of impacted teeth shown in three-dimensional computed tomographic images (3D Dental-computed tomography (CT) images) and plain radiographs and to determine whether 3D Dental-CT images are useful for examination before performing an operation for extraction of a maxillary impacted tooth. METHODS AND PATIENTS Images obtained from patients who had impacted teeth in the maxilla, including impacted mesial supernumerary teeth in 13 patients, impacted incisors in two patients, impacted canines in 11 patients, impacted premolars in four patients and impacted molars in three patients, were used in this study. In all patients, plain radiographs and 3D Dental-CT images were retrospectively reviewed by an oral radiologist for evidence of root dilaceration before operations to extract the impacted teeth were performed. The findings in the images were compared with intraoperative findings in all cases. RESULTS The mean specificity and sensitivity of plain radiographs were 95 and 8%, respectively, while those of 3D Dental-CT images were 100 and 77%, respectively. There was a statistically significant (P<0.01) difference between the depiction capabilities of plain radiographs and 3D Dental-CT images with regard to dilacerations of roots of impacted teeth. DISCUSSION AND CONCLUSION CT may enable radiologists to make a quick and accurate diagnosis of tooth impaction. 3D Dental-CT images are useful for determining the root shape of an impacted tooth in the maxilla.

A method of reducing susceptibility artifacts in MRI of the head and neck region

Methods of reducing susceptibility artifacts, which invariably occur in MRI examinations of the head and neck region, were investigated in healthy subjects and in patients with head and neck disease. It was found that MRI examination of the head and neck region can be improved by setting the readout direction in the axial cross-sectional image in the anteroposterior direction and by making TE as small as possible.

CT Angiography of the Head and Neck : A Report of 5 Cases

We report on five cases in which patients were examined with CT angiography (CTA). In two cases of facial arteriovenous malformation (AVM), the dilated vascular structure was clearly visible. Moreover, three-dimensional reconstruction allowed observation of the relationship to the bone and comparison with the skin surface. The maximum intensity projection (MIP) image was useful for understanding the spatial relationship between the embolic material and the residual AVM. We also constructed three-dimensional subtraction images. In these images, only the blood vessels and lesion site were visible as bright areas, making it easy to determine the volume of the lesion.CT angiography can be used as a screening method for observing blood vessels and is useful for detailed examination of the relationship between lesions and blood vessels, and for examination of hypervascular lesions.

Broken fragment of the mandibular third molar tooth in the floor of the mouth

It is not unusual for a part of the tooth root to break off during tooth extraction. In the case of maxil lary tooth extractions, careless procedure can sometimes result in aberrat ion of the root into the maxi l lary sinus. Aberrat ion of the mandibular tooth root by extraction is relatively rare. We report here a case of aberrat ion of part of the tooth root into the oral floor. The pat ient was a 24-year-old man, who was diagnosed with partial eruption of the lower third molar and who underwent tooth extract ion at a local clinic. During the operation, the dentist noticed that part of the root had broken off. As the fragmented root tip could not be found in the extraction cavity, aberrat ion into the oral floor was suspected. Extraction of the root fragment under local anesthesia was judged to be difficult, and the patient was referred to our dental hospital 2 days later. Plain CT was performed. Conventional axial tomographic images were taken. The axial image showed a high-density area on the r ight side of the oral floor, which was thought to be the aberrant lower third molar root fragment. It was indicated that the root fragment had first been located above the mylohyoid muscle and then moved to near the posterior border of the mylohyoid muscle (Fig. l-d). As a partial bone defect was seen in the inferiorly lingual cortical bone of the socket, it was considered that the fragmented root tip was pushed out of the mandible by force (Fig. l-b, c). Coronal reconstruction and three-dimensional reconstruction of the images were performed. Both images clearly showed the positional relationship between the extract ion cavity and the partial deficiency of cortical bone and aberrant tooth (Fig. l-e, f). Extraction of the aberrant root was performed under general anesthesia, and it was confirmed that the root fragment was located behind the mylohyoid muscle, above the submandibular gland. According to the oral surgeon, the information obtained from the preoperative CT was very useful for the operation planning.

Characteristic findings of adenoid cystic carcinoma on MR imaging and differentiation from squamous cell carcinoma

Ten patients with adenoid cystic carcinoma and 49 with squamous cell carcinoma confirmed by aiopsy were evaluated. In these patients, malignant tumors were suspected with clinical progressions and clinical symptoms. The purpose of this study was to analyze and discuss the characteristic findings on MR imaging of adenoid cystic carcinoma in the head and neck, and to examine the usefulness of MR imaging in the differentiation between adenoid cystic carcinoma and squamous cell carcinoma. The characteristics on MR imaging of adenoid cystic carcinoma are a high signal intensity on T2-weighted images, marked enhancement by Gd-DTPA, and a capsular structure. All cases of recurrent adenoid cystic carcinomas also showed upward extension. We consider that the high signal intensity on T2-weighted images, the marked contrast enhancement and the capsular structure in MR imaging can be useful in differentiating adenoid cystic carcinoma and squamous cell carcinoma.

Energy metabolism in the masseter muscle: A comparison of normal subjects and TMD patients using31P-MRS

Abstract31P-MRS (Magnetic Resonance Spectroscopy) is the only noninvasive technique capable of measuring high-energy phosphate compounds in muscle tissue. In this study, we used31P-MRS to analyze the energy metabolism at rest in the masseter muscle of TMD patients who showed clinical symptoms in the masseter muscles. The subjects were 10 TMD patients who had complaints of pain and contracture in the masseter muscles, and 10 normal subjects.1.A clear decrease in PCr in the masseter muscle tissue was seen in all of the patients in this study.2.A clear increase in Pi in the TMD patients was not seen despite a decrease in PCr.3.The difference in pH between the normal subjects and TMD patients was not significant. In the TMD patients, the recovery of the PCr was delayed, because of that, a decrease of PCr was suggested by31P-MRS.

Dynamic MRI of head and neck carcinomas

To evaluate the utility of dynamic MRI, we reviewed 28 patients with head and neck carcinomas. Dynamic images demarcated the extension of tongue carcinomas more clearly than spin-echo images. Time-intensity curves were useful to distinguish tumours from other tissues and to predict the vascularity and recurrence of the tumours.

Unusual CT finding in neck lymph node involved by lymphoma

Squamous cell carcinoma is the most common malignant lesion in the head and neck. Although neck adenopathy is generally thought to be a metastasis from a primary soite. On the other hand, lymphoma is the most common primary malignancy in the extralaryngeal portion of the neck and is the most frequent cause of unilateral neck mass in patients 20-40 years of age. In contrast to squamous ceil carcinoma, lymph nodes involved by lymphoma usually do not show central necrosis before treatment. A 76-year-old woman was referred to our hospital with a chief complaint of pharyngeal pain in January 1992. Physical examination revealed diffuse swelling at the base of the tongue. MRI showed that the suspected tumor mass lesion was located at the left base of the tongue and tonsillar pillar (Fig, 1). Axial CT image showed a clear central necrotic finding at the left upper neck (Fig. 2) which was suggestive of primary squamous cell carcinoma involving the tongue and tonsillar pillar with metastasis to a neck lymph node. However, histopathological examination of a biopsy specimen indicated nonHodgkins lymphoma.

Evaluation of an in vivo labeling method of red blood cells with99mTc-pertechnetate in the head and neck region

Seventeen cases in which red blood cells (RBCs) were labeled with99mTc (99mTc-RBC method) are reviewed to confirm the vascular nature of lesions. This study was undertaken to see whether the99mTc-RBC method is useful in terms of detecting angiomatous lesions, and also to determine the indications for this method. In one case, total removal revealed a good, correlation between the range of uptake and the actual tumor size. MR images definitively demonstrated tumor location and extension. When hemangioma is suspected, MR examination is the preferred modality to determine tumor extension, tumor mass, and invasion into the surrounding tissue. However, when it is suspected that the MR image is poor due to bulky metal artifacts, as in the case of dental prostheses, the99mTc-RBC method should be used because this method is only slightly influenced by metal artificts. In addition, this method should be applied when whole body screening is needed.

Radiological findings of progressive systemic sclerosis accompanied by polymyositis in plain radiography

Progressive systemic sclerosis (scleroderma) is a multisystem disorder of unknown etiology characterized by fibrosis of the skin, blood vessels, and visceral organs including the gastrointestinal tract, lungs, heart, and kidneys. Polymyositis is a condition of unknown etiology in which the skeletal muscle i~ disturbed by a nonsuppurative inf lammatory process dominated by lymphocytic infiltration. The term polymyositis is applied when the condition spares the skin. One-third of the cases with polymyositis are associated with various connective tissue disorders, such as mixed connective tissue disorder and progressive systemic sclerosis (scleroderma), and one-tenth of the cases are associated with a malignancy. According to current estimates, the annual incidence of in f l ammatory myopathies is about five in one million. In this paper, we report on a case of progressive systemic sclerosis accompanied by polymyositis. A 51-year-old woman with progressive systemic sclerosis, proven by a skin biopsy, was refered to a dental office for examination and treatment for difficulty of mouth opening. This case with progressive systemic sclerosis was associated with polymyositis, but not with a malignancy. The progressive systemic sclerosis involved the skin, the fingers, and the lungs. The disease first occured when the patient was about 20 years old. The patient had difficulty of mouth opening, bilateral temporomandibular arthralgia, and spasticity of the skin. Characteristic findings of progressive systemic sclerosis were recognized on plain rag iography. P a n o r a m i c r ad iog raphy showed bone absorption in the bilateral angle of the mandible. The borders were smooth and the bony cortex remained as a thin layer. Bone erosion was recognized in the bilateral mandibular condyles and the right coronoid process (Figs. 1,2), and the borders were irregular. On the four divisional images of the temporomandibular joint, the bilateral mandibular condyles hardly moved between mouth opening and closing (Fig. 3). Oral Radiol. Vol.lO No.2 1994(149~150)