E Honda

Artifacts from Dental Casting Alloys in Magnetic Resonance Imaging

The potential advantage of magnetic resonance imaging (MRI) has been limited by artifacts due to the presence of metallic materials. For quantitative evaluation of the magnitude of artifacts from dental casting alloys and implant materials in MR imaging, 11 dental casting or implant materials were imaged by means of 1.5 T MRI apparatus with three different sequences. Mean and standard deviation of water signal intensity (SI) around the sample in the region of interest (1200 mm2) were determined, and the coefficient of variation was compared for evaluation of the homogeneity of the SI. A variety of artifacts with different magnitudes was observed. Only one of the samples, composed mainly of Pd, In, and Sb, showed no artifacts in all imaging sequences. We concluded that selection of specific dental casting alloys according to their elemental compositions could minimize the metal artifacts in MRI; however, titanium alloys currently pose a problem with respect to causing MRI artifacts.

Effects of Head and Body Position on Two- and Three-dimensional Configurations of the Upper Airway

This study was carried out to test the hypothesis that changes in head/body position induce changes in upper-airway dimensions. Contiguous images were obtained by means of magnetic resonance imaging in normal awake subjects during nasal breathing. A statistical analysis was made on 5 consecutive slices, including the most constricted sites in both the retropalatal and retroglossal regions. Dimensional changes in the upper airway in association with changes in head/body position were evaluated. In the retropalatal region, there was a significant decrease in the lateral dimension in the lateral recumbent position compared with that in the supine position. The cross-sectional area in the retroglossal region was significantly increased in both the supine with the head rotated and lateral recumbent positions. This change was accompanied by significant volumetric changes in the retroglossal region. Thus, sleeping with the head rotated may be effective for improving upper-airway obstruction.

Effect of titrated mandibular advancement and jaw opening on the upper airway in nonapneic men: a magnetic resonance imaging and cephalometric study☆☆☆

The aim of this study was to examine adaptive changes in the cross-sectional area of the upper airway during mandibular advancement and jaw opening and to explore whether these changes are directly related to morphologic features of the mandible. Fourteen nonapneic men participated in this study. A custom-made oral device was used to keep the mandible at 0% (F(0)V(0)), 50% (F(50)V(0)), 75% (F(75)V(0)), or 100% (F(100)V(0)) of maximum advancement, and at 50% (F(75)V(50)), 75% (F(75)V(75)), or 100% (F(75)V(100)) of maximum gape at F(75)V(0). Magnetic resonance imaging was used to investigate differences in the upper-airway cross-sectional area in these 7 positions. To eliminate excessive individual variation, changes in the mean (mean%) and minimum (min%) cross-sectional area of the upper airway were calculated as percentages of those at F(0)V(0). Cephalograms were taken to analyze morphologic features of the mandible. A dose-dependent change was seen when the mandible was advanced. The min% in F(100)V(0) was significantly greater than those in F(50)V(0) and F(75)V(0). The change in the upper airway size varied between subjects during jaw opening. At F(75)V(0), the min% of the whole upper airway was significantly associated with morphologic features of the mandible, such as the mandibular plane angle and lengths of the mandibular body and ramus.

Modulation transfer function evaluation of cone beam computed tomography for dental use with the oversampling method

OBJECTIVESnThe aim was to investigate the possibility of evaluating the modulation transfer function (MTF) of cone beam CT (CBCT) for dental use using the oversampling method.nnnMETHODSnThe CBCT apparatus (3D Accuitomo) with an image intensifier was used with a 100 mum tungsten wire placed inside the scanner at a slight angle to the plane perpendicular to the plane of interest and scanned. 200 contiguous reconstructed images were used to obtain the oversampling line-spread function (LSF). The MTF curve was obtained by computing the Fourier transformation from the oversampled LSF. Line pair tests were also performed using Catphan(R).nnnRESULTSnThe oversampling method provided smooth and reproducible MTF curves. The MTF curves revealed that the spatial resolution in the z-axis direction was significantly higher than that in the axial direction. This result was also confirmed by the line pair test.nnnCONCLUSIONSnMTF analysis was performed successfully using the oversampling method. In addition, this study clarified that the 3D Accuitomo had high spatial resolution, especially in the z-axis direction.

Application of MRI movie for observation of articulatory movement during a fricative /s/ and a plosive /t/

OBJECTIVEnTo use an accurate method of tooth visualization in magnetic resonance imaging (MRI) movie for the observation of spatio-temporal relationships among articulators.nnnMATERIALS AND METHODSnThe subjects were two volunteers. Each subject repeated a vowel-consonant-vowel syllable (ie, /asa/; /ata/), and the run was measured using a gradient echo sequence. A custom-made clear retainer filled with the jelly form of ferric ammonium citrate was then fit onto the dental arch, and a T1-weighted turbo-spin-echo sequence was taken. Landmarks were used for superimposition of the incisor boundary onto sequential images of MRI movie. Tracings were conducted to observe the spatio-temporal relationships among articulators.nnnRESULTSnThe incisor boundary was clearly visible in the magnetic resonance images. After superimposition, the contact distance of the tongue to palate/incisor was found to be longer during /t/-articulation than during /s/-articulation. There were prominent differences in images with and without tooth superimposition in the front oral cavity.nnnCONCLUSIONSnThe method could distinctly extract a tooth boundary in MRI. Detailed configurational relationships between the tongue and tooth were observed during the production of a fricative and a plosive in MRI movie using this method.

Combined fMRI and MRI movie in the evaluation of articulation in subjects with and without cleft lip and palate

Objective: This study was undertaken to explore the application of functional magnetic resonance imaging (fMRI) and MRI movies in the evaluation of articulatory function in subjects with and without cleft lip and palate (CLP). Design: The authors examined brain activation and the dynamic movement of articulators during bilabial and velar plosives using fMRI and MRI movies. Subjects: Two subjects, one with unilateral cleft lip and palate (UCLP) and one with bilateral cleft lip and palate (BCLP), and 12 non-CLP volunteers. Results: Activation foci were found in the precentral gyrus, thalamus, and cerebellum in non-CLP volunteers. In comparison, similar regions were activated in the UCLP subject during both plosives, whereas the regions activated in the BCLP subject were different, particularly during the velar plosive. The dynamic movement of articulators in the UCLP subject was comparable to that in a non-CLP volunteer but different from that in the BCLP subject. Conclusions: The results suggest that these two MRI modalities may be a promising evaluation methodology for articulatory function in CLP from central and peripheral perspectives.

Dental radiographic signs characteristic to Hallermann-Streiff syndrome

A review of the literature and examination of a personally observed case led to the conclusion that anterior displacement of the temporomandibular joints provides a useful diagnostic criterion for the Hallermann-Streiff syndrome.

Distinctive cortical articulatory representation in cleft lip and palate: a preliminary functional magnetic resonance imaging study.

Objective: To investigate cortical representation of articulation of the bilabial plosive in patients with cleft lip and palate. Design: We examined cortical representation for /pa/-articulation in cleft lip and palate patients using blood oxygenation level–dependent functional magnetic resonance imaging. Subjects: Data from four postsurgical adult cleft lip and palate patients were compared with those from six healthy volunteers. Results: Activation foci were found in the bilateral primary sensorimotor cortex in all cleft lip and palate patients, as in the controls. The sensorimotor cortex ipsilateral to the side of cleft lip and palate showed greater activation in unilateral cleft lip and palate patients, whereas the sensorimotor cortex contralateral to the side on which cheiloplasty had been performed earlier showed greater activation in a bilateral cleft lip and palate patient. Conclusions: The results suggest that there may be an ipsilateral dominance in cortical representation during bilabial articulation to the side of the cleft in the upper lip.

Condylar appearance in panoramic radiograms of asymptomatic subjects and patients with temporomandibular disorders

The usefulness and the limitations of panoramic radiography for the diagnosis of temporomandibular (TM) disorders were evaluated. The condylar shape appearance and the osseous changes were evaluated in asymptomatic 150 subjects (control subjects) and in 142 patients with the TM disorders who were examined by panoramic radiography. The position of the flattening and the osseous changes including osteophyte, bone erosion and osteosclerosis were objectively analyzed to determine the condylar shape. The incidence of the composite flattening type, which exhibits flattening on both the anterior and on other surfaces, was three times higher in the TM patients compared to controls. Thus, this composite type may indicate the presence of TM disorders. The incidence of osseous changes in the patients with TM disorders was significantly higher than controls and increased further in the group with the permolar and/or molar missing. This suggests that the occlusion of molar, teeth is an important factor related to the development of the TM disorders. It was concluded that panoramic radiography was useful for detecting TM disorders, at least in those with osseous changes or flattening.The usefulness and the limitations of panoramic radiography for the diagnosis of temporomandibular (TM) disorders were evaluated. The condylar shape appearance and the osseous changes were evaluated in asymptomatic 150 subjects (control subjects) and in 142 patients with the TM disorders who were examined by panoramic radiography. The position of the flattening and the osseous changes including osteophyte, bone erosion and osteosclerosis were objectively analyzed to determine the condylar shape. The incidence of the composite flattening type, which exhibits flattening on both the anterior and on other surfaces, was three times higher in the TM patients compared to controls. Thus, this composite type may indicate the presence of TM disorders. The incidence of osseous changes in the patients with TM disorders was significantly higher than controls and increased further in the group with the permolar and/or molar missing. This suggests that the occlusion of molar, teeth is an important factor related to the development of the TM disorders. It was concluded that panoramic radiography was useful for detecting TM disorders, at least in those with osseous changes or flattening.

Abstracts—Dental radiology Vol. 37, 1997

s--Dental Radiology Vol.38, 1998 Evaluation of CT Images on Metastasis to Cervical Lymph Node in Patients with Oral Cancer T o m o k a z u FUJIKI , T o r u W A K A S A * , Yoshinobu YANAGI* , Yasu tosh i HONDA*, N o r i k o K A W A I * , Kanj i KISHI* and T a k u r o u W A D A D e p a r t m e n t of Oral and Max i l l o f ac i a l Radio logy, M a t s u m o t o Denta l Univers i ty * D e p a r t m e n t of Oral Radiology, O k a y a m a Univers i ty Dental School There have been many reports about the usefulness of CT in diagnosing cervical lymph node metastasis from oral cancer. With relatively high diagnostic accuracy, various diagnostic criteria have been used. This study evaluated CT images of cervical lymph node metastasis in patients with oral cancer using these criteria. Eighty-nine cases of various oral cancers (132 lymph node groups) were evaluated regarding cervical lymph node metastasis. In patients with nodes measuring over I cm in minimal axial diameter, 58.1% were metastat ic ( m e t a s t a t i c / t o t a l = 4 7 / 7 4 ) , while 17.2 % of patients with nodes measuring less than 1 cm in minimal axial diameter of lymph node were metastat ic (10 / 58). As for other diagnostic criteria, in patients with spherical nodes, 38.7 % ( m e t a s t a t i c / t o t a l = 2 9 / 7 5 ) , in patients showing ring enhancement, 70.4 % (19/27) and in patients with fusion, 75.0 % (3 /4) were metastatic. In addition, in patients with spherical nodes measuring over 1 cm in minimal axial diameter, 59.5 % (22 / 37), in patients with nodes measuring over I cm in minimal axial diameter and showing ring enhancement, 78.3 % (18 / 23), in patients with spherical nodes showing ring enhancement, 60.0 % (9 / 15) and in patients with spherical nodes measuring over 1 cm in minimal axial diameter and showing ring enhancement, 64.3 % (9 / 14) were metastatic. In case of disappearance of fat layer (1 / 1), cancer infiltration of the surrounding tissue was seen. In conclusion, over 1 cm in minimal axial diameter, spherical node and ring enhancement were found to be appropriate diagnostic criteria. Furthermore, CT is essential in diagnosing cervical lymph node metastasis from oral cancer. Dental Radiology 1998; 38(1): 3-9 Evaluation of Venous Involvement with Oral and Neck Legions by CT-Angiography Yasuh iko M O R I T A , T a k a s h i H I R A O K A , Tuyosh i S A T O and T a k e n o r i N O I K U R A D e p a r t m e n t of Dental Radiology, K a g o s h i m a Univers i ty Dental School Intravenous contrast enhancements were employed in eight cases at CT to evaluate the involvement of head and neck lesions at the neck ar tery and vein. Cases were branchial cyst, inflammation of the oral floor, a hemangioma, and five malignant tumors. A total of 100ml contrast enhancement media (240mg/ ml iodine) was injected using a automatic injector at a speed of 0.7~l.0ml/sec. A spiral CT (Somatom Plus, Siemens, Germany) was used in this study. Spiral scans with 3~5mm slice thichness and the table speed of 3~5mm/rota t ions were performed at data acquisition. Three scans were usually performed before, during, and just after enhancement. Images were reconstructed every one or two mm from the data during enhancement. The relations between the lesions and artery and vein were observed using cine-mode display. The results showed that 1) Involvement with malignant tumor: Two cases which were diagnosed as free from involvement with tumors at artery were correctly diagnosed in corresponding to clinical findings at surgery and follow-up examination. Other three cases were diagnosed as having tumors at the arteries. In case No.5, diagnosed as having tumor involvement, the external