[Show abstract][Hide abstract] ABSTRACT: Background: The aim of this study is to apply a tooth-visualized 3-T video magnetic resonance imaging (MRI) method for evaluating articulatory movement in normal-bite and anterior open-bite subjects. Methods: Six healthy women with normal occlusion and a woman with 2-mm dental anterior open bite were recruited. The subjects were scanned with use of a 3-T MRI scanner while producing a vowel-consonant-vowel syllable (/asa/). A gradient echo sequence (fast low angle shot) with a segmented cine and a parallel imaging technique (generalized auto-calibrating partially parallel acquisitions) was used. Then, subjects wore customized clear plates containing contrast agent gel and were scanned again with a turbo spin-echo sequence. Facial landmarks were used as references to superimpose the MRI images. The articulatory movements of all subjects were analyzed using the superimposed images. Results: The tongue of the open-bite subject moved more anteriorly than that of the normal-bite subjects when producing the same consonant sound. Conclusion: A tooth-visualized 3-T MRI video is an effective method for objective diagnosis of variation in articulatory movement of the anterior open-bite subject.
Full-text · Article · Apr 2015 · Journal of the World Federation of Orthodontists
[Show abstract][Hide abstract] ABSTRACT: To determine the optimal diagnostic criterion of dynamic contrast-enhanced MRI (DCE-MRI) for predicting salivary gland malignancy using a dynamic sequence with high temporal resolution, as well as the accuracy of this technique.
The DCE-MRI findings of 98 salivary gland tumors (74 benign and 24 malignant) were reviewed. MR images were sequentially obtained at 5-sec intervals for 370 sec. Two parameters, peak time and washout ratio, were determined from the time-signal intensity curve. The optimal thresholds of these parameters for differentiating benign and malignant tumors were determined, along with the diagnostic accuracy of the criterion using these thresholds.
A peak time of 150 sec and a washout ratio of 30% were identified as optimal thresholds. As the criterion for malignancy, the combination of peak time <150 sec and washout ratio <30% provided a sensitivity of 79% (19/24), specificity of 95% (70/74), and overall accuracy of 91% (89/98). Three of the 5 false-negative cases were malignant lymphomas of the parotid gland.
Peak time <150 sec with washout ratio <30% comprised the optimal diagnostic criterion in predicting salivary gland malignancy, providing a sensitivity of 79% and specificity of 95%. The use of high temporal resolution might improve the accuracy of DCE-MRI. Advances in knowledge: Although several studies have reported the usefulness of DCE-MRI in the differential diagnosis of salivary gland tumors, the specific diagnostic criteria employed have differed widely. We determined the optimal criterion and its accuracy using a dynamic sequence with high temporal resolution.
Full-text · Article · Mar 2015 · The British journal of radiology
[Show abstract][Hide abstract] ABSTRACT: Objective.
Different bony structures can affect the function of the velopharyngeal muscles. Asian populations differ morphologically, including the morphologies of their bony structures. The purpose of this study was to compare the velopharyngeal structures during speech in two Asian populations: Japanese and Thai.
Ten healthy Japanese and Thai females (five each) were evaluated with a 3-Tesla (3 T) magnetic resonance imaging (MRI) scanner while they produced vowel-consonant-vowel syllable (/asa/). A gradient-echo sequence, fast low-angle shot with segmented cine and parallel imaging technique was used to obtain sagittal images of the velopharyngeal structures.
MRI was carried out in real time during speech production, allowing investigations of the time-to-time changes in the velopharyngeal structures. Thai subjects had a significantly longer hard palate and produced shorter consonant than Japanese subjects. The velum of the Thai participants showed significant thickening during consonant production and their retroglossal space was significantly wider at rest, whereas the dimensional change during task performance was similar in the two populations.
The 3 T MRI movie method can be used to investigate velopharyngeal function and diagnose velopharyngeal insufficiency. The racial differences may include differences in skeletal patterns and soft-tissue morphology that result in functional differences for the affected structures.
Full-text · Article · Mar 2015 · BioMed Research International
[Show abstract][Hide abstract] ABSTRACT: Purposes
Neurovascular compression (NVC) of the trigeminal nerve is the primary cause of trigeminal neuralgia (TN), but is known to occur in both symptomatic and asymptomatic nerves. The purposes of this study were to evaluate the relationship between the MRI findings regarding the site of NVC and the manifestation of TN symptoms.
In 147 patients with unilateral TN, the presence or absence of NVC was evaluated on MRI in both symptomatic and asymptomatic nerves. In cases with NVC, the shortest distance from the trigeminal nerve root to the responsible vessel was measured.
The mean distance from the trigeminal nerve root to the site of NVC in asymptomatic nerves (3.85±2.69 mm) was significantly greater than that in symptomatic nerves (0.94±1.27 mm). When the distance was 3mm or less, the rate of the manifestation of TN symptoms was 83.1% (103/124). On the other hand, it was only 19.6% (9/46) in cases with a distance of greater than 3mm.
Whether or not NVC of the trigeminal nerve was symptomatic was closely related to the distance from the trigeminal nerve root to the responsible blood vessel.
No preview · Article · Sep 2014 · Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology
[Show abstract][Hide abstract] ABSTRACT: Objectives
The aim of this study was to reveal the three-dimensional fluctuation of voxel values in a uniform material placed inside a phantom simulating a human head when it was scanned with cone-beam computed tomography (CBCT) for dental use.
We employed a cylindrical acrylic phantom to simulate a human head. Iodine solution, water, or air was placed inside the phantom, which was then scanned using CBCT. Regions of interest (ROIs) were set on the obtained CBCT images, and the mean voxel value in each ROI was measured. Finally, the profiles of the voxel values in the bottom-to-top (BT) and anterior-to-posterior (AP) directions in the field of view (FOV) were investigated.
For the BT direction, the voxel values were almost constant regardless of the slice position (standard deviation: <10.0 for each material). However, in the AP direction, the profiles showed different tendencies depending on the contents of the acrylic phantom. When iodine solution or air was scanned, the profiles showed a cupping shape, as the voxel values in the epicenter were lower than those in the periphery of the FOV. In contrast, when water was placed in the phantom, the profiles showed a capping shape, as the voxel values in the epicenter were higher.
Three-dimensional fluctuation of voxel values was evaluated for uniform scan targets on CBCT scanning. In the longitudinal direction, the voxel values were almost constant. However, in the axial plane, the fluctuation was so large that estimation from voxel values might not be reliable.
[Show abstract][Hide abstract] ABSTRACT: Objective: To develop MRI movie in 3T MRI scanner, which can reveal clear articulation with only few artifacts combined with tooth visualization for better understanding in articulation.
Method: Various concentrations of MRI contrast media (Ferric Ammonium Citrate: FAC) were prepared and tested before experiment. The optimum concentration of media was used to prepare as facial markers and contrast agent gel. Customized maxillary and mandibular plates with space around the central incisors were also prepared. Custom-made circuitry was connected to 3T MRI scanner that used to observe articulation. T1-weighted gradient echo (FLASH) with segmented cine and parallel imaging technique (GRAPPA) pulse sequence was used. The mid-sagittal plane image was obtained with time resolution of 9ms, matrix size of 128x128, pixel size of 1x2 mm, slice thickness of 4 mm and acceleration factor of 2. The subject was in the supine position and produced fricative sound (/asa/) synchronized with the external trigger pulse. Then, the subject was asked to wear plates filled with contrast agent gel for taking teeth boundaries image. The MRI movie images were superimposed with the teeth boundaries image by using facial landmark as references.
Result: Continuous 116 images with 9-ms time resolution were obtained. Compared with 1.5T, the number of pronunciation repetition was decreased (42 times in 1.5T, 35 times in 3T). When the time resolution was 31.5ms, it was possible to reduce the number of repetition of 1/3. The optimum concentration of FAC solution in 3T was twofold for 1.5T. The 3T MRI image quality was improved with few motion and contrast media artifacts.
Conclusion: 3T movie MRI is powerful and non-invasive method that can clearly reveal articulation. Because of the higher time resolution than normal video, the variation of speech function can be diagnosed.
[Show abstract][Hide abstract] ABSTRACT: We assessed the effect of teeth clenching on handgrip force behaviorally, and investigated cortical activity during the occurrence of facilitatory effects using functional magnetic resonance imaging (fMRI). Twenty-three participants were assessed as to whether they had habitual teeth clenching during maximal voluntary contraction (MVC) exertion, and 21 of them were identified to have such a habit. For those participants, behavioral testing showed that MVC with clenching was greater compared with without clenching (approximately 108% greater on average). Next, cortical activity was measured under gripping with clenching (GwC), gripping without clenching (GwoC), and teeth clenching (C) conditions. We found that the activity of the hand region in primary motor cortex (M1), cingulate motor area/supplementary motor area (CMA/SMA) and anterior cerebellum (AC) was greater in contrast of GwC vs. (GwoC+C). Furthermore, significant correlation was observed between the increasing ratio of the handgrip force and the % signal change in the hand region of M1 and AC, but not in CMA/SMA. These results suggest that the activation in the hand region of M1 and AC may facilitate the spinal motoneurons, and the activation in the hand region in M1 by clenching may be due to a signal from CMA/SMA.
Full-text · Article · Dec 2013 · Neuroscience Research
[Show abstract][Hide abstract] ABSTRACT: This study evaluates the spatial resolution of cone beam computed tomography for dental use (CBCT) via modulation transfer function (MTF) analyses.
Two models of CBCT system, 3DX FPD8 and FineCube v.12, were used. MTF analysis was applied to each CBCT system using a thin tungsten wire technique.
The MTF curves in the radial direction on the XY-plane were concordant regardless of position, whereas the curves in the azimuthal direction tended to decrease as the distance from the rotation center increased. In the Z-axis direction, the MTF curve of the medial level of the field of view was superior to that of any other level.
The spatial resolution of CBCT systems depends on the location within the field of view. Because the spatial resolution was the highest in the medial level and rotation center position, an object should be placed at this position during a CBCT examination.
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to investigate the imaging characteristics of peripheral nerve sheath tumors (PNSTs) in the jaw.
Imaging studies of 6 patients were retrospectively reviewed. Conventional radiography, computed tomography, and magnetic resonance imaging were performed in all patients.
A fusiform lesion continuous with the nerve was observed in 2 cases, with the tumor arising within the inferior alveolar canal. In the other 4 cases, with the tumor arising outside the canal, the tumor had protruded and eroded into the bone. Protrusion was also present in 1 of the 2 cases, with the tumor arising within the canal. A target or fascicular sign was observed each in 1 case.
A fusiform lesion continuous with the nerve and a target or fascicular sign was only present in a few cases. The PNSTs, however, showed a tendency to protrude into the bone.
[Show abstract][Hide abstract] ABSTRACT: Purpose:
The aim of this study was to compare panoramic and paraxial views of dental CT reformatted images to detect the mandibular canal, and to evaluate the usefulness of the dental CT software function of "Outlining the Mandibular Canal in the Panoramic View".
One hundred and fifty-five patients (310 sides), who underwent multi-slice computed tomography examination for pretreatment planning of dental implant were analyzed. After scanning, two types of dental CT reformatted image, panoramic and paraxial views were obtained. Two oral radiologists evaluated both views for the visibility of the mandibular canal using a 5-point rating scale: score 5, 100-80% visible, to score 1, 20-0% visible. The visibility scores of the two views were evaluated and compared by Wilcoxon's signed rank test.
The mean ± standard deviations of panoramic and paraxial views were 4.2 ± 1.1 and 3.5 ± 1.2, respectively, and the former was significantly higher than the latter (p < 0.001). On the basis of these results, we attempted to apply the function of "Outlining the Mandibular Canal in the Panoramic View" to cases with poor visibility of the canal (score 1, 2 or 3) on paraxial views. Consequently, we could reduce the number of such cases from 128 (41%) to 56 (18%).
The detectability of the mandibular canal was significantly higher in panoramic views than in paraxial views. Using the function of "Outlining the Mandibular Canal in the Panoramic View", the precision for identifying the canal on paraxial views was considered to be improved.
[Show abstract][Hide abstract] ABSTRACT: To evaluate the visibility of the superior and inferior borders of mandibular canal using panoramic radiography (PR) and cross-sectional computed tomography (CT) images.
Digital panoramic images and cross-sectional CT images of 100 patients were evaluated. The mandibular canal was divided into 4 areas of equal width (1-4), from anterior to posterior. The visibility of the superior and inferior borders was assessed using a 5-point visibility scoring system, with lower scores for worse visibility.
For both modalities, the superior border showed significantly lower score than the inferior border in all areas. For the superior border, areas 1, 2, and 3 all showed significantly lower scores than area 4 for PR, whereas only area 1 showed a lower score than area 4 for CT.
The visibility of the superior border was very poor on panoramic images. The use of cross-sectional CT images remarkably improved this poor visualization.
[Show abstract][Hide abstract] ABSTRACT: Objective
Owing to the complexity of the human language, numerous individuals develop different types of speech disorders. Some patients with cleft lip and/or palate (CLP) exhibit compensatory misarticulations (CMAs), which decrease speech fluency and interfere with the intelligibility of the speaker. The glottal stop (GS) is representative of CMAs in CLP patients. The glottal stop results from an occlusion or lack of airflow at the level of the glottis. In the context of speech therapy for CLP patients, intelligibility is usually used as an outcome measure. However, little is known about the behavioral and neurobiological mechanisms involved in the perception of speech produced by an individual with CMAs. We aimed to investigate the perception of GS compared to normal articulation (NA) using behavioral and neuroimaging experiments.Materials and methodsTwenty healthy subjects without CMAs listened to auditory stimuli (NA and GS) and were asked to distinguish NA from GS using the button-press response during functional magnetic resonance imaging (fMRI).ResultsThe reaction time for the perception of GS was significantly longer than that for NA. Additionally, the activation area and the percentage signal change in the auditory cortex were larger when the subjects listened to GS compared to NA. The auditory association area, which controls the higher-level processing of auditory signals, exhibited more intense bilateral activation in response to GS as compared to NA.Conclusions
In subjects without GS, the perception of GS sounds may require more auditory attention and more complex auditory processing than the perception of NA sounds.
Full-text · Article · Feb 2013 · Journal of Oral Biosciences
[Show abstract][Hide abstract] ABSTRACT: Objectives:
The aims of this study were to evaluate the ability of [F]fluorodeoxyglucose (F-FDG)-PET/computed tomography (CT) to identify tumor recurrence, nodal metastases, and distant metastases for surveillance and discuss the optimal timing of F-FDG-PET/CT examination after the completion of treatment for head and neck malignancy.
A total of 319 patients who underwent a post-treatment F-FDG-PET/CT examination for head and neck malignancy were studied. F-FDG-PET/CT findings were compared with the final diagnosis confirmed by histopathological examinations or clinical and radiological follow-up for at least 6 months. Patients were divided into two groups according to the presence or absence of clinical suspicion of recurrent disease. The diagnostic accuracy of F-FDG-PET/CT was analyzed for each group. Patients were also categorized according to the time interval between the completion of treatment and the post-treatment F-FDG-PET/CT examination. Differences in diagnostic accuracy due to the time interval were also evaluated.
The diagnostic accuracy of F-FDG-PET/CT was high for both groups. The overall accuracy of F-FDG-PET/CT performed within 2 months (69%) after the completion of treatment was significantly inferior to that performed after 2 months (93%).
F-FDG-PET should be performed immediately for patients with clinically suspected recurrent disease. In others, it should be performed at later than 2 months after the completion of the treatment.
No preview · Article · Nov 2012 · Nuclear Medicine Communications
[Show abstract][Hide abstract] ABSTRACT: Objectives:
The aim of this study was to investigate characteristic MRI findings of rheumatoid arthritis (RA) in the temporomandibular joints (TMJs).
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.
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.
Severe osseous changes in the condyle and synovial proliferation were considered characteristic MRI findings of RA in the TMJs.
No preview · Article · Jul 2012 · Dentomaxillofacial Radiology
[Show abstract][Hide abstract] ABSTRACT: Objective: The speech-related central nervous system (CNS) may be subdivided into motor-imaginary and -execution speech subsystems. However, it is unknown whether either or both of these subsystems differ in subjects with and without cleft lip and palate (CLP). The purpose of this study was to clarify whether there was a difference in brain activation patterns during speech between these groups.
Method: Two subjects with left unilateral CLP (UCLP), four with bilateral CLP (BCLP) and six healthy subjects participated in this study, and only one subject with BCLP showed compensatory misarticulation (CMA). We compared brain activation patterns during overt (O) and covert (C) articulation using functional magnetic resonance imaging (fMRI). A 1.5T MR scanner provided T2*-weighted gradient echo–type echo planar images. The subjects were instructed to produce the consonant-vowel syllable /ka/ in a normal tone (O-task) or to generate this syllable in their mind (C-task) when a green circle was presented on a screen, and to remain at rest when a red circle was presented.
Result: In the C-task, there were no significant differences in the activation patterns between subjects with and without CLP. In the O-task, motor-related areas including the premotor and primary sensorimotor cortices and the cerebellum were activated in subjects with UCLP and BCLP without CMA, which generally resembled the activation patterns in healthy subjects. On the other hand, the posterior cingulate gyrus, but not motor-related areas, was activated in the BCLP subject with CMA.
Conclusion: There may be a slight difference in the brain activation pattern for motor-imaginary articulation between subjects with and without CLP. However, there might be significant differences in brain activation patterns for the execution of articulation between subjects with and without CMA, regardless of the presence or type of CLP.
[Show abstract][Hide abstract] ABSTRACT: 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).
Six patients with histopathologically confirmed TMJ cysts who were examined by MRI were included in this study. Two oral radiologists retrospectively evaluated MR images.
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.
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.