Yukihiro Iida

Use of sonographic elastography of the masseter muscles for optimizing massage pressure: a preliminary study

To examine the stiffness of the masseter muscle using sonographic elastography and to investigate its relationship with the most comfortable massage pressure in the healthy volunteers. In 16 healthy volunteers (10 men and 6 women), the Masseter Stiffness Index (MSI) was measured using EUB-7000 real-time tissue elastography. They underwent massages at three kinds of pressures using the Oral Rehabilitation Robot (WAO-1). A subjective evaluation regarding the comfort of each massage was recorded on the visual analogue scale. Elastography was also performed in two patients with temporomandibular joint dysfunction with the myofascial pain. The mean MSI of the right and left muscles in the healthy volunteers were 0.85 +/- 0.44 and 0.74 +/- 0.35 respectively. There was no significant difference between the right and left MSI in the healthy volunteers. The MSI was related to massage pressure at which the healthy men felt most comfortable. The two temporomandibular disorder patients had a large laterality in the MSI. The MSI was related to the most comfortable massage pressure in the healthy men. The MSI can be one index for determining the massage pressure.

Automated scheme for measuring mandibular cortical thickness on dental panoramic radiographs for osteoporosis screening

Findings of dental panoramic radiographs (DPRs) have shown that the mandibular cortical thickness (MCT) was significantly correlated with osteoporosis. Identifying asymptomatic patients with osteoporosis through dental examinations may bring a supplemental benefit for the patients. However, most of the DPRs are used for only diagnosing dental conditions by dentists in their routine clinical work. The aim of this study was to develop a computeraided diagnosis scheme that automatically measures MCT to assist dentists in screening osteoporosis. First, the inferior border of mandibular bone was detected by use of an active contour method. Second, the locations of mental foramina were estimated on the basis of the inferior border of mandibular bone. Finally, MCT was measured on the basis of the grayscale profile analysis. One hundred DPRs were used to evaluate our proposed scheme. Experimental results showed that the sensitivity and specificity for identifying osteoporotic patients were 92.6 % and 100 %, respectively. We conducted multiclinic trials, in which 223 cases have been obtained and processed in about a month. Our scheme succeeded in detecting all cases of suspected osteoporosis. Therefore, our scheme may have a potential to identify osteoporotic patients at an early stage.

Development of a robot which can simulate swallowing of food boluses with various properties for the study of rehabilitation of swallowing disorders

Many patients suffer from swallowing disorders (dysphagia). There are many treatments for these disorders, such as swallowing therapy, surgery, and dietary modification. In our study, we focuse on dietary modification, a common approach. Normally, the swallowing is affected by food bolus properties such as hardness, stickiness and rheological characteristics, and dietary modifications can prevent swallowing disorder patients from suffering dysphagia (aspiration), as well as promote good nutrition. Based on these facts, our goal is to find foods which do not cause dysphagia, and develop food for swallowing disorder patients accordingly. Therefore, we are proposing an in-vitro Dynamic VFSS (Video Fluorographic Swallowing Study) simulation system which uses advanced robotics technology to mimic the dynamic process of swallowing and monitors the status and movement of the food bolus inside the system, for objective evaluation of the swallowing process. The dynamic VFSS simulation system consists of a head, mandible, neck, tongue, pharynx, and larynx which reproduce human anatomy. It is driven by 16 actuators with wire driving mechanisms. In this paper, we will present the dynamic VFSS simulation unit in detail. In addition, we will detail a set of the experiments carried out to determine whether food bolus properties can affect dysphagia or not. To observe the movement of the food bolus, we use a Video Fluoroscopy (VF) unit. The results of the experiments show that thickened boluses have a tendency to leave residue in the epiglottic vallecula. In contrast, liquids cause less residue, and increase the risk of dysphagia (aspiration). Moreover, this study shows that the frontal image, as well as the lateral image, is important for evaluating residual food in the oral- pharyngeal space.

An automatic detection method for carotid artery calcifications using top-hat filter on dental panoramic radiographs

The purpose of this study is to develop an automated carotid artery calcification (CAC) detection scheme on dental panoramic radiographs (DPRs). The CAC is one of the indices for predicting the risk of arteriosclerosis. First, regions of interest (ROIs) that include CACs were determined on the basis of inflection points of the mandibular contour. Initial CAC candidates were detected by using a grayscale top-hat filter and simple grayscale thresholding technique. Finally, a rule-based approach and support vector machine to reduce the number of false positive (FP) findings were applied using features such as area, location, and circularity. Thirty-four DPRs were used to evaluate the proposed scheme. The sensitivity for the detection of CACs was 93.6% with 4.4 FPs per image. Experimental results showed that our computer-aided detection scheme may be useful to detect CACs.

Videofluorographic Evaluation of Mastication and Swallowing of Japanese Udon Noodles and White Rice

A videofluorographic (VF) swallowing study was performed on 22 healthy volunteers to observe the complete mastication and swallowing phases for Japanese udon noodles and white rice. The hardness, stickiness, and cohesiveness of food samples were measured using a food texture analyzing system. VF images were acquired using a versatile fluoroscopic unit and barium sulfate was used as a contrast medium. Udon noodles had a harder and smoother food texture than white rice. Fewer chewing movements and more stage 2 transport were seen during the consumption of udon noodles than for white rice.

Improved inspection of the lateral pharyngeal recess using cone-beam computed tomography in the upright position

ObjectivesTo evaluate the structure of the lateral pharyngeal recess (LPR) and surrounding structures in computed tomography (CT) images obtained from subjects in the supine and upright positions.MethodsSix subjects were evaluated using cone-beam CT (CBCT) in the upright position, and with a four-row multidetector helical CT (MDCT) in the supine position. All of the voxel sizes were adjusted to 0.3 × 0.3 × 0.3 mm3 in the x, y, z coordinate system. The posterior nasal spine and basion were used as references. The LPR and surrounding structures were measured and compared in the two different modalities.ResultsIn 83% of the cases, the LPR was deeper when the position was changed from supine to upright.ConclusionsOur results suggest that imaging of the LPR using CBCT with the subject in the upright position is superior to that using MDCT with the subject in the supine position.

A morphological comparison of the piriform sinuses in head-on and head-rotated views of seated subjects using cone-beam computed tomography

ObjectivesFood flow in the oropharynx changes when the head is rotated. The purpose of this study was to evaluate morphological differences in the upper and lower piriform sinuses in head-on (HO) versus head-rotated (HR) positions.MethodsTen healthy adult volunteers with no previous history of dysphagia were subjected to cone-beam computed tomography (CBCT) in the HO and HR positions. Binary CBCT images were created at 50% gray scale to examine morphological changes in the lower piriform sinuses.ResultsUpon rotation to the right, the cross-sectional area of the left lower piriform sinus increased significantly (P = 0.037). The depth of the right lower piriform sinus also increased significantly (P = 0.011) upon rotation. The volume of the lower piriform sinuses increased significantly on both sides (right, P = 0.009; left, P = 0.013). The upper piriform sinuses acquired a teardrop shape, with the rotated side narrowed and opposite side enlarged.ConclusionsThese results suggest that changes in food flow during head rotation result mainly from changes in the size and shape of the upper piriform sinuses.

A new screening pathway for identifying asymptomatic patients using dental panoramic radiographs

To identify asymptomatic patients is the challenging task and the essential first step in diagnosis. Findings of dental panoramic radiographs include not only dental conditions but also radiographic signs that are suggestive of possible systemic diseases such as osteoporosis, arteriosclerosis, and maxillary sinusitis. Detection of such signs on panoramic radiographs has a potential to provide supplemental benefits for patients. However, it is not easy for general dental practitioners to pay careful attention to such signs. We addressed the development of a computer-aided detection (CAD) system that detects radiographic signs of pathology on panoramic images, and the design of the framework of new screening pathway by cooperation of dentists and our CAD system. The performance evaluation of our CAD system showed the sensitivity and specificity in the identification of osteoporotic patients were 92.6 % and 100 %, respectively, and those of the maxillary sinus abnormality were 89.6 % and 73.6 %, respectively. The detection rate of carotid artery calcifications that suggests the need for further medical evaluation was approximately 93.6 % with 4.4 false-positives per image. To validate the utility of the new screening pathway, preliminary clinical trials by using our CAD system were conducted. To date, 223 panoramic images were processed and 4 asymptomatic patients with suspected osteoporosis, 7 asymptomatic patients with suspected calcifications, and 40 asymptomatic patients with suspected maxillary sinusitis were detected in our initial trial. It was suggested that our new screening pathway could be useful to identify asymptomatic patients with systemic diseases.

Effect of head rotation on the pathway of a food bolus through the pharynx as evaluated by a videofluoroscopic swallow study

PurposesHead rotation is widely used as a postural technique for dysphagic patients. In this study, we evaluated the effects of head rotation on pharyngeal swallowing in healthy subjects.MethodsA videofluoroscopic swallow study (VFSS) of pharyngeal swallowing was performed on subjects with the head in neutral (upright and full-faced) and rotated positions. Seventeen volunteers were given samples of liquid barium and custard pudding mixed with barium to swallow.ResultsVFSS findings revealed that the head-rotated swallow causes the bolus to lateralize away from the direction of head rotation. Satisfactory lateralization of the food or liquid bolus during a head-rotated swallow was observed in approximately 80% of cases with liquid barium and in 60% of those with material of pudding consistency. A spillage of bolus into the pharynx before swallow initiation occurred in only approximately 15% of cases when a subject rotated his/her head.ConclusionIn this study, the effects of head rotation on pharyngeal swallowing in healthy subjects were evaluated. Results from this study suggest that the efficacy of head rotation is affected by the consistency of food and liquid materials.

Evaluation of age-related changes with cross-sectional CT imaging of teeth

Tooth pulp atrophy occurs with increasing age. An age estimation procedure using dental cone beam computed tomography (CBCT) imaging was developed. Clinical dental CBCT images of 60 patients (aged from 20 to 80 years) were evaluated. The ratio of the cross-sectional area of the pulp cavity to the cross-sectional area of the tooth (pulp cavity ratio) was calculated. The pulp cavity ratio in the labio-lingual plane of the mandibular anterior teeth and the mesio-distal plane of the maxillary anterior teeth was strongly correlated with the patients’ age. The pulp cavity ratio of anterior teeth may be a useful parameter for estimating age.