Biomedical subjects

Wangdo Kim

Publications and source records attributed to Wangdo Kim.

8 recordsLinked to original sources

PubMed2006

Wound measurement by curvature maps: a feasibility study.

A non-contact wound measurement method by laser scanner and curvature maps is presented. A patient's foot ulcer is scanned by FastSCAN ten times over a three-week period. With the surface's 3D coordinates, curvature maps of the ulcerous area are calculated. Utilizing a specified rim curvature value, the wound edge is detected and processed via cubic spline smoothing, which is qualitatively verified by a photograph. Subsequently, the depth, area and volume of the wound can be calculated. The results indicate that laser scanning followed by curvature analysis might be a potential clinical tool for non-contact measurement of wounds.

Feasibility Studies↗

PubMed2005

Estimation of the axis of a screw motion from noisy data--a new method based on Plücker lines.

The problems of estimating the motion and orientation parameters of a body segment from two n point-set patterns are analyzed using the Plücker coordinates of a line (Plücker lines). The aim is to find algorithms less complex than those in conventional use, and thus facilitating more accurate computation of the unknown parameters. All conventional techniques use point transformation to calculate the screw axis. In this paper, we present a novel technique that directly estimates the axis of a screw motion as a Plücker line. The Plücker line can be transformed via the dual-number coordinate transformation matrix. This method is compared with Schwartz and Rozumalski [2005. A new method for estimating joint parameters from motion data. Journal of Biomechanics 38, 107-116] in simulations of random measurement errors and systematic skin movements. Simulation results indicate that the methods based on Plücker lines (Plücker line method) are superior in terms of extremely good results in the determination of the screw axis direction and position as well as a concise derivation of mathematical statements. This investigation yielded practical results, which can be used to locate the axis of a screw motion in a noisy environment. Developing the dual transformation matrix (DTM) from noisy data and determining the screw axis from a given DTM is done in a manner analogous to that for handling simple rotations. A more robust approach to solve for the dual vector associated with DTM is also addressed by using the eigenvector and the singular value decomposition.

Acceleration↗

PubMed2005

The analysis of golf swing as a kinematic chain using dual Euler angle algorithm.

The manner in which anatomical rotation from an individual segment contributes to the position and velocity of the endpoint can be informative in the arena of many athletic events whose goals are to attain the maximal velocity of the most distal segment. This study presents a new method of velocity analysis using dual Euler angles and its application in studying rotational contribution from upper extremity segments to club head speed during a golf swing. Dual Euler angle describes 3D movement as a series of ordered screw motions about each orthogonal axis in a streamlined matrix form-the dual transformation matrix- and allows the translation and rotation component to be described in the same moving frame. Applying this method in biomechanics is a novel idea and the authors have previously applied the methodology to clinical studies on its use in displacement analysis. The focus of this paper is velocity analysis and applications in sports biomechanics. In this study, electrogoniometers (Biometrics, UK) with a frequency of 1000 Hz were attached to a subject during the execution of the swing to obtain the joint angles throughout the motion. The velocity of the club head was then analyzed using the dual velocity which specifies the velocity distribution of a rigid body in screw motion at any point in time as the dual vector. The contributions of each segment to the club-head velocity were also compared. In order to evaluate this method, the calculated position and velocity of the club head were compared to the values obtained from video image analysis. The results indicated that there is good agreement between calculated values and video data, suggesting the suitability of using the Dual Euler method in analyzing a kinematic chain motion.

Algorithms↗

PubMed2005

Passive motion characteristics of the talocrural and the subtalar joint by dual Euler angles.

The objective of this study is to validate previous descriptions of hindfoot kinematics using dual Euler angle methods in a passive cadaveric model. The dual Euler angle method was chosen so as to facilitate description of the translational and rotational movement occurring at both the ankle and subtalar joints. A non-metal experimental set-up was fabricated to generate motion in foot cadaver specimens. Three-dimensional kinematic data of the ankle joint complex was collected from ten knee-below foot cadaver specimens using a 'Flock of Birds' electromagnetic tracking device. The data correlates well with previously published kinematic descriptions of the ankle subtalar joint complex. Both the ankle and subtalar joint show 6 degree of freedom motion and multiaxial characteristics. The motions of the talocrural joint, the talocalcaneal joint, and the gross motion between the foot and the shank were analyzed. During dorsiflexion-plantarflexion the motion of the calcaneus with respect to the tibia occurs mainly at the ankle joint, with little motion at the subtalar joint. The subtalar joint contributes more than the ankle joint during inversion-eversion.

Algorithms↗

PubMed2005

Tibial torsion measurement by surface curvature.

BACKGROUND: Tibial torsion is the angle between the transverse axes of the proximal and distal tibial articular surfaces. It measures the degree of twisting of the tibia around its own longitudinal axis. The accurate measurement on the magnitude of tibial torsion is of great use in monitoring derangements. It is also useful as a baseline in the event of surgical intervention. Various methods have been developed but none of them have gained wide acceptance. Even the CT scan technique, which is considered the "gold standard", produces varying results when executed by different researchers. A quick, objective and non-invasive method is thus very much needed for the effective monitoring of tibial torsion in clinical environments. METHODS: Eighteen adult men's lower legs were scanned by a laser scanner to give the surface coordinates of the leg surfaces. By calculating curvature maps of legs from the 3D coordinates, stable anatomical landmarks such as the lateral and medial malleoli can be located. The angle indicating the degree of tibial torsion can then be derived from these landmarks. FINDINGS: The objective determination of the various anatomical landmarks results in a reproducible measure of tibial torsion. The results obtained in this study are generally in agreement with the measurements reported previously. INTERPRETATION: The reproducibility of the results allows for the objective observation, monitoring and comparison of tibial torsion over time and across subjects. It allows also for the development of a system of measurement that is fast, convenient, accurate and radiation-free.

Bone Diseases↗

PubMed2005

Determining dual Euler angles of the ankle complex in vivo using "flock of birds" electromagnetic tracking device.

The dual Euler angles method has been proposed as an alternative approach to describe the general spatial human joint motion. In this study, the dual Euler angles method was applied to study the three-dimensional motion of the ankle complex. The methodology for obtaining dual Euler angles of the ankle complex was developed by using a "Flock of Birds" electromagnetic tracking device. The repeatability of the methodology was studied based on the intertester and intratester variability analysis. Finally kinematic coupling characteristics of the ankle complex during dorsiflexion-plantarflexion, eversion-inversion, and abduction-adduction were analyzed according to the parameters of the dual Euler angles.

Algorithms↗

PubMed2004

Analysis of passive motion characteristics of the ankle joint complex using dual Euler angle parameters.

OBJECTIVE: To apply the dual Euler angles method to investigate the passive motion characteristics of the human ankle joint complex. DESIGN: Three-dimensional kinematic data of the ankle joint complex was collected from 10 knee-below foot cadaver specimens. BACKGROUND: Besides the Euler angles and screw axis methods, the dual Euler angles method has been proposed as an alternative approach to quantify general spatial human joint motion. The dual Euler angles method provides a way to combine rotational and translational joint motions and to interpret motions in Cartesian coordinate systems, which can avoid the problems caused by the use of the joint coordinate system due to non-orthogonality. METHODS: A non-metal experimental setup was fabricated to generate motion in foot cadaver specimens. The kinematic data during passive dorsiflexion-plantarflexion was measured using an electromagnetic tracking device. RESULTS: The kinematic coupling characteristics and the respective contribution of the ankle joint and the subtalar joint to the gross motion of the foot with respect to the shank were analyzed based on dual Euler angle parameters. The results obtained in this study are generally in agreement with the observations reported previously. CONCLUSIONS: The dual Euler angles method is suitable for analyzing the motion characteristics of the ankle joint complex. The motion at the ankle joint complex involves rotations about and translations along three axes.

Algorithms↗

PubMed2002

Use of dual Euler angles to quantify the three-dimensional joint motion and its application to the ankle joint complex.

This paper presents a modified Euler angles method, dual Euler angles approach, to describe general spatial human joint motions. In dual Euler angles approach, the three-dimensional joint motion is considered as three successive screw motions with respect to the axes of the moving segment coordinate system; accordingly, the screw motion displacements are represented by dual Euler angles. The algorithm for calculating dual Euler angles from coordinates of markers on the moving segment is also provided in this study. As an example, the proposed method is applied to describe motions of ankle joint complex during dorsiflexion-plantarflexion. A Flock of Birds electromagnetic tracking device (FOB) was used to measure joint motion in vivo. Preliminary accuracy tests on a gimbal structure demonstrate that the mean errors of dual Euler angles evaluated by using source data from FOB are less than 1 degrees for rotations and 1mm for translations, respectively. Based on the pilot study, FOB is feasible for quantifying human joint motions using dual Euler angles approach.

Algorithms↗