Won-Jin Yi

A System for Ubiquitous Health Monitoring in the Bedroom via a Bluetooth Network and Wireless LAN

Advances in information technology have enabled ubiquitous health monitoring at home, which is particularly useful for patients, who have to live alone. We have focused on the automatic and unobtrusive measurement of biomedical signals and activities of patients. We have constructed wireless communication networks in order to transfer data. The networks consist of Bluetooth and Wireless Local Area Network (WLAN). In this paper, we present the concept of a ubiquitous-Bedroom (u-Bedroom) which is a part of a ubiquitous-House (u-House) and we present our systems for ubiquitous health monitoring.

Classification of Parkinson gait and normal gait using Spatial-Temporal Image of Plantar pressure

The purpose of this paper is the classification of Spatial-Temporal Image of Plantar pressure (STIP) among normal step and the patients step of Parkinson disease. For this, we created a new image data, STIP, that have information of the change of plantar pressure during heel to toe motion (i.e., contain spatial and temporal information for plantar pressure). To get STIP, the walking of 21 patients with Parkinson disease and 17 age-matched healthy subjects were recorded and analyzed using in-shoe dynamic pressure measuring system with comfort walking. For feature extraction of gait, we applied Principal component analysis (PCA) to STIP and calculated weights of STIP on each principal components. Then, we build hard margin Support Vector Machine (SVM) classifier for gait recognition and test of generalization performance using normalized weights on PCs of STIP. SVM result indicated an overall accuracy of 91.73% by the RBF(Radial Basis Function) kernel function. These results demonstrate considerable potential in applying SVMs in gait classification for many applications.The purpose of this paper is the classification of Spatial-Temporal Image of Plantar pressure (STIP) among normal step and the patients step of Parkinson disease. For this, we created a new image data, STIP, that have information of the change of plantar pressure during heel to toe motion (i.e., contain spatial and temporal information for plantar pressure). To get STIP, the walking of 21 patients with Parkinson disease and 17 age-matched healthy subjects were recorded and analyzed using in-shoe dynamic pressure measuring system with comfort walking. For feature extraction of gait, we applied Principal component analysis (PCA) to STIP and calculated weights of STIP on each principal components. Then, we build hard margin Support Vector Machine (SVM) classifier for gait recognition and test of generalization performance using normalized weights on PCs of STIP. SVM result indicated an overall accuracy of 91.73% by the RBF(Radial Basis Function) kernel function. These results demonstrate considerable potential in applying SVMs in gait classification for many applications.

Relationship between the curve of Spee and dentofacial morphology evaluated with a 3-dimensional reconstruction method in Korean adults

INTRODUCTION The purposes of this study were to examine the curve of Spee of the maxillary and mandibular arches by using a 3-dimensional reconstruction method and to determine the relationship between the curve of Spee and dentofacial morphology with multiple regression analysis. METHODS Lateral cephalograms and dental models were evaluated from 18 Korean men and 31 Korean women. The depth of the curve of Spee was measured on the virtual dental models with computer software. Seventeen cephalometric variables related to the lateral cephalograms were analyzed to determine differences in dentofacial morphology. The Pearson correlation analysis and a multiple linear regression analysis were performed to determine the relationship between the curve of Spee as the dependent variable and other cephalometric and dental variables as the independent variables. RESULTS The depth of the curve of Spee in the mandibular arch was significantly related to overbite, overjet, and the sagittal position of the mandible with respect to the anterior cranial base. The curve of Spee was not affected by sex. CONCLUSIONS These results will assist in the determination of the sagittal organization of the teeth as a reference for prosthetic restoration and orthodontic treatment.

Comparison of effective dose for imaging of mandible between multi-detector CT and cone-beam CT

Purpose The aim of this study was to compare the effective dose for imaging of mandible between multi-detector computed tomography (MDCT) and cone-beam computed tomography (CBCT). An MDCT with low dose technique was also compared with them. Materials and Methods Thermoluminescent dosimeter (TLD) chips were placed at 25 organ sites of an anthropomorphic phantom. The mandible of the phantom was exposed using 2 different types of MDCT units (Somatom Sensation 10 for standard-dose MDCT, Somatom Emotion 6 for low-dose MDCT) and 3 different CBCT units (AZ3000CT, Implagraphy, and Kavo 3D eXaM). The radiation absorbed dose was measured and the effective dose was calculated according to the ICRP 2007 report. Results The effective dose was the highest for Somatom Sensation 10 (425.84 µSv), followed by AZ3000CT (332.4 µSv), Somatom Emotion 6 (199.38 µSv), and 3D eXaM (111.6 µSv); it was the lowest for Implagraphy (83.09 µSv). The CBCT showed significant variation in dose level with different device. Conclusion The effective doses of MDCTs were not significantly different from those of CBCTs for imaging of mandible. The effective dose of MDCT could be markedly decreased by using the low-dose technique.

Comparison of trabecular bone anisotropies based on fractal dimensions and mean intercept length determined by principal axes of inertia

The mechanical quality of trabecular bone depends on both its stiffness and its strength characteristics, which can be predicted indirectly by the combination of bone volume fraction and architectural anisotropy. To analyze the directional anisotropy of the trabecular bone, we applied the fractal geometry technique to plain radiographs. The anisotropy of the bone was quantified from an ellipse, based on the directional fractal dimensions (FD), by the principal axes of inertia. The anisotropies based on the FD were compared with those determined using the common method of mean intercept length (MIL). The directional FD gave the fractal information obtained from a projection along the MIL orientation. For this reason, the spatial variations associated with the bone length in any direction were manifested in a related frequency band of the power spectrum determined along the direction. The directional FD and MIL plots were highly correlated, although they originated from quite different geometries. Of the angle, premolar, and incisor regions of the human mandible, the anisotropies calculated using both FD and MIL showed the highest correlation in the trabecular bone of the angle region. The method using directional FDs as determined by the principal axis of inertia measures the anisotropy directly, using two-dimensional plain radiographs. This kind of method will be a useful to provide better estimates of bone quality in vivo compared with the density measurements alone, especially for the indirect diagnosis of jawbone quality in dental clinics.

Correlation between 3-dimensional facial morphology and mandibular movement during maximum mouth opening and closing

PURPOSE The purpose of this study was to analyze the relationship between mandibular movement and facial morphology parameters measured using 3-dimensional CT data. MATERIALS AND METHODS We have developed a mandibular movement tracking and simulation system. The mandibular movement data were acquired from 22 subjects (6 males and 16 females), 3 who had no clinical facial deformities and 19 who had orthofacial deformities. The subjects voluntarily performed maximum mouth opening and closing movements. Three-dimensional maximum linear movements of selected points (bilateral condylions, infradentale, and pogonion) were calculated to represent mandibular movement. Facial morphology values were measured 3-dimensionally from CT data and bilateral morphological values were divided into 2 groups according to the mandibular deviation, the deviated side, and counter-deviated side groups. Correlation coefficients were calculated to evaluate the relationship between mandibular movements and facial morphology. RESULTS Maximum linear movements of all selected points on the mandible were positively correlated with sella-nasion-point A (SNA) and sella-nasion-point B (SNB). Movements of the infradentale and pogonion were significantly correlated with ramus inclination, lateral mandibular body angle, ramus length, and mandibular body length. Condylar movement was positively correlated with lateral mandibular body angle and mandibular body length. Multiple stepwise linear regression analysis was performed to evaluate the model predicting the effect of morphological values on mandibular movement. Condylar movement was associated with the SNA (R(2) value = 0.32 for the deviated side, R(2) value = 0.26 for the counter-deviated side), and movement of the infradentale was associated with both SNA and ramus length (R(2) value = 0.57). Movement of the pogonion could be predicted by SNA, mandibular length, and condylar head length (R(2) value = 0.65). CONCLUSION The 3D facial morphology values were associated with variations in mandibular movement, and morphological parameters contributed to predicting the movement of the mandible with different degrees.

The relationship between three-dimensional principal rotations and mandibular deviation

OBJECTIVE To investigate the rotational variations of three-dimensional (3D) trajectories at anatomic landmarks by different mandibular kinematics, we applied principal axes of inertia to the 3D trajectories. The principal rotations were determined directly from the anatomy-based trajectories produced by a patient-specific temporomandibular joint simulation. As a preliminary study, the principal rotations for a pilot group of patients with mandibular deviation were correlated with the deviation. STUDY DESIGN Three-dimensional mandibular movements from the patients with mandibular deviation were tracked based on a patient-specific splint and an optical tracking system. The dental occlusion recorded on the splint provided synchronization for initial movement in the tracking and the simulation phases. The translation and rotation recorded during tracking were applied sequentially to the mandibular model in relation to a fixed maxilla model. The sequential positions of the points of interest based on the reference coordinate system could also be simulated and traced by the same method. The landmarks selected for analysis were the points of the bilateral condyles and of the mandibular incisor. The moment of inertia tensor was calculated with respect to the 3D trajectory points. Using the unit vectors along the principal axes derived from the tensor matrix, α, β, and γ rotations (horizontal, sagittal, and frontal planes) around the z-, y-, and x-axes, respectively, were determined to represent the principal directions as principal rotations. RESULTS The measured rotations were correlated with the deviation in 3 orthogonal planes. Under the influence of the mandibular asymmetry, the orientations of the principal axis at the condyles increase counterclockwise in the horizontal plane and clockwise in the frontal plane. At the incisor point, the horizontal and frontal angles increase counterclockwise, but the sagittal angles increase clockwise. The interrelations between different rotations and between landmarks, defined as a correlation coefficient between principal rotations, decrease as the deviation increases. CONCLUSIONS Three-dimensional trajectories at selected landmarks based on the reference coordinate system were evaluated using principal axes of inertia to investigate the functional characteristics of the mandible with a deviation. The movement asymmetry between the condyles increases as the deviation increases in all directions. The principal rotations at the condyles can be explained by those at the incisor with varying degrees despite the deviation.

Predicting the configuration of a C-shaped canal system from panoramic radiographs

OBJECTIVE To characterize the presentation of C-shaped canals in mandibular molars on dental panoramic radiographs. STUDY DESIGN The sample consisted of 290 patients who had undergone both panoramic dental radiography and computed tomography (CT). Initially the presence of mandibular molars with C-shaped canals was identified on this sample by the use CT. This was used as a ground radiographic truth. Then 3 investigators independently classified the mandibular molars according to their 6 root morphologies on panoramic dental radiographs. The sensitivities, specificities, positive predictive values (PPV), and negative predictive values (NPV) of characteristic findings on panoramic radiographs were calculated. RESULTS A C-shaped canal was identified in 90 (29%) of 311 mandibular molars. The most common morphology of C-shaped canal molars was 2 separate conical roots (52%); trabecular patterns were relatively common between the roots. In contrast, the most common morphology of molars without C-shaped canals was 2 separate roots that were either divergent or parallel (85%). CONCLUSION Panoramic radiography is a good surveying modality to detect C-shaped canals and can be used to determine whether further examination is required before endodontic treatment.

Directional disorder of ciliary metachronal waves using two-dimensional correlation map

The interrelationship of cilia and the order of wave directions are important factors that determine the effectiveness of cilia to transport materials in mucociliary systems of the respiratory tract. The interrelationship of cilia and the directional disorder of the ciliary metachronal wave were analyzed using digital microscopic images. The degree of synchronization between ciliary beats was determined by the correlation factor between two different spots. To find out the uniphase directions of beating cilia, principal axes of inertia were applied to the two-dimensional correlation map calculated from sequential ciliary images. The standard deviation of determined wave directions in a region of interest (ROI) was defined as a measure of metachronal wave disorder. The pooled mean of metachronal wave disorder was 23.4 /spl plusmn/ 8.79/spl deg/ in ROIs of 8 /spl mu/m /spl times/ 8 /spl mu/m and 25.4 /spl plusmn/ 6.46/spl deg/ in 32 /spl mu/m /spl times/ 24 /spl mu/m from the sphenoid sinus mucosa of five normal subjects. Our result shows that there is a considerable variation in metachronal wave directions of cilia beating on the epithelium.

Texture analysis of mandibular cortical bone on digital dental panoramic radiographs for the diagnosis of osteoporosis in Korean women

OBJECTIVE To determine whether individual measurements or a combination of textural features and mandibular cortical width (MCW) derived from digital dental panoramic radiographs (DPRs) are more useful in assessment of osteoporosis. STUDY DESIGN Textural features were obtained by using fractal dimension (FD) and gray-level co-occurrence matrix (GLCM). Digital DPRs and bone mineral densities (BMDs) of the lumbar spine and the femoral neck were obtained from 141 female patients. A naïve Bayes classifier, a k-nearest neighbor (k-NN) algorithm, and a support vector machine were assessed for classifying osteoporosis. RESULTS The combinations of FD plus MCW (95.3%, 92.1%, 96.8%) and GLCM plus MCW (93.7%, 89.5%, 94.2%) for femoral neck BMD showed the highest diagnostic accuracy with the use of the naïve Bayes, k-NN, and support vector machine classifiers, respectively. CONCLUSIONS The combination of textural features and MCW contributed a better assessment of osteoporosis compared with the use of only individual measurements.