Jeong Hwan Seo

An enhanced algorithm for knee joint sound classification using feature extraction based on time-frequency analysis

Vibroarthrographic (VAG) signals, generated by human knee movement, are non-stationary and multi-component in nature and their time-frequency distribution (TFD) provides a powerful means to analyze such signals. The objective of this paper is to improve the classification accuracy of the features, obtained from the TFD of normal and abnormal VAG signals, using segmentation by the dynamic time warping (DTW) and denoising algorithm by the singular value decomposition (SVD). VAG and knee angle signals, recorded simultaneously during one flexion and one extension of the knee, were segmented and normalized at 0.5 Hz by the DTW method. Also, the noise within the TFD of the segmented VAG signals was reduced by the SVD algorithm, and a back-propagation neural network (BPNN) was used to classify the normal and abnormal VAG signals. The characteristic parameters of VAG signals consist of the energy, energy spread, frequency and frequency spread parameter extracted by the TFD. A total of 1408 segments (normal 1031, abnormal 377) were used for training and evaluating the BPNN. As a result, the average classification accuracy was 91.4 (standard deviation +/-1.7) %. The proposed method showed good potential for the non-invasive diagnosis and monitoring of joint disorders such as osteoarthritis.

Portable measurement system for the objective evaluation of the spasticity of hemiplegic patients based on the tonic stretch reflex threshold.

The clinical scales used for the evaluation of the spasticity have some drawbacks, in spite of their simplicity and ease of assessment, and their inter- and intra-rater reliability remains controversial. The aim of this study is to develop a portable system for the objective and reliable evaluation of the spasticity based on the K-means clustering of the tonic stretch reflex threshold (TSRT) and to compare the discrimination performance of the level of spasticity determined by our method with that by the conventional modified Ashworth scale (MAS). Fifteen hemiplegic patients (7 males and 8 females, age: 63.5±15.6) participated in the study. The average and standard deviation values of the TSRTs were 127.9±1.6, 121.8±1.5 and 117.9±1.3 in groups G1, G2 and G3, respectively, and there were significant differences between the TSRTs of each group (p<0.05). Also, our groups classified by the criteria of the TSRT had a strong negative correlation (r=-0.95, r(2)=0.90, p<0.05) between the level of spasticity and TSRTs. These results demonstrated that our system could be clinically more useful for the quantitative and reliable discrimination of the spasticity than the conventional MAS.

An Acoustical Evaluation of Knee Sound for Non-invasive Screening and Early Detection of Articular Pathology

Knee sound signals generated by knee movement are sometimes associated with degeneration of the knee joint surface and such sounds may be a useful index for early disease. In this study, we detected the acoustical parameters, such as the fundamental frequency (F0), mean amplitude of the pitches, and jitter and shimmer of knee sounds, and compared them according to the pathological conditions. Six normal subjects (4 males and 2 females, age: 28.3u2009±u20092.3xa0years) and 11 patients with knee problems were enrolled. The patients were divided into the 1st patient group (5 males and 1 female, age: 30.2u2009±u200910.3xa0years) with ruptured wounds of the meniscus and 2nd patient group (2 males and 3 females, age: 42.1u2009±u200916.2xa0years) with osteoarthritis. The mean values of F0, jitter and shimmer of the 2nd patient group were larger than those of the normal group, whereas those of the 1st patient group were smaller (pu2009<u20090.05). Also, the F0 and jitter in the standing position were larger than those in the sitting position in both the 1st and 2nd patient groups (pu2009<u20090.05). These results showed good potential for the non-invasive diagnosis and early detection of articular pathologies via an auscultation.

Estimation algorithm of the bowel motility based on regression analysis of the jitter and shimmer of bowel sounds

Bowel sound (BS) signals can be used clinically as useful indicators of bowel motility. In this study, we devised a modified iterative kurtosis-based detector algorithm, in order to enhance the de-noising performance of BS signals, and an estimation algorithm of bowel motility based on the regression modeling of the jitter and shimmer of BS signals obtained by auscultation. The correlation coefficient, coefficient of determination and errors between the colon transit times measured by a conventional radiograph and the corresponding values estimated by our method were 0.987, 0.974 and 3.5 ± 3.3h, respectively. These results demonstrated that our method could be used as a complementary tool for the non-invasive diagnosis and monitoring of bowel motility, instead of conventional radiography.

The acoustical analysis of knee joint sounds for non-invasive diagnosis of articular pathology

We have evaluated and classified arthritic pathology using the acoustical analysis of knee joint sounds. Six normal subjects and 11 patients with knee problem were enrolled and patients were divided into the 1st patient group needed an orthopaedic surgery because of the ruptured wounds of meniscus or ACL (anterior cruciate ligament) and 2nd patient group diagnosed as osteoarthritis. In sitting and standing position, subjects flexed and extended the knee joint, the sounds and angle of knee joint were collected. Dynamic time warping was applied for normalizing a time-axis. The fundamental frequency, the mean amplitude of pitch, jitter, shimmer were analyzed according to a position and unpaired T-test and ANOVA test were used for statistic results. The experimental results showed that the fundamental frequency of the 2nd patient group or standing groups was higher than the others and the pitch of sounds was varied unstably.

Real-time, High-resolution Diagnosis for Osteoarthritis in the Rat Using Common-Path Fourier-Domain Optical Coherence Tomography

The need for an inexpensive, real-time, high-resolution diagnosis for osteoarthritis (OA) is profound. After inducing OA in rats, we monitored the degradation of the articular cartilage by experimentally using in-house developed common-path Fourier-domain optical coherence tomography (CP-FDOCT). To observe the progression of OA, we injected monosodium iodoacetate (MIA) into the left knee joint. The histological images showed patterns that are similar to OCT images. These results illustrated the potential of CP-FDOCT for use in the noninvasive diagnosis of this particular grade of OA.

Implementation of a Multi-functional Ambulatory Urodynamics Monitoring System Based on Newly Devised Abdominal Pressure Measurement

The measurement of the rectal pressure is considered to be the ‘gold standard’ for the assessment of the abdominal pressure. However, conventional rectal catheters can cause erroneous results and are not comfortable for the patients. To reduce these problems, we devised a non-invasive technique for the measurement of the abdominal pressure using the parametric curve fitting method, based on linear, polynomial, exponential or sine equation modeling, between the rectal pressure and electromyographic (sEMG) signals recorded simultaneously from the abdomen. The sEMG signals and rectal pressure were obtained simultaneously from 12 patients with neurogenic bladders due to spinal cord injury (ageu2009=u200953.2u2009±u200911.9xa0years, BMIu2009=u200924.4u2009±u20092.7, ASIA classification: D). Using our algorithm, the correlation coefficient and root mean square error (RMSE) between the measured and estimated abdominal pressure obtained by the quartic polynomial modeling were 0.86u2009±u20090.05 and 4.70u2009±u20091.56, respectively. The results obtained herein suggest that the sEMG signals can be used reliably for the indirect measurement of the abdominal pressure in ambulatory urodynamics monitoring systems.

High-resolution morphological features of the muscle and cartilage in vivo using optical coherence tomography based on super luminescent diode

We have demonstrated a polarization sensitive cartilage and muscle imaging based on common path optical coherence tomography (CP-OCT) using near infrared source. The axial and lateral resolutions of our PS-OCT system are 9µm and 6µm, respectively. The internal structural information has been extracted by the real-time signal analysis (Fourier Transform) from the modulated spectral intensity depending on the beam and tissue birefringence. Preliminary results using fresh beef and in vivo rat show that we can visualize the birefringence effect of the tissue collagen fibers in the samples for better image contrast and sensitivity for detection of hidden dermal structures. Compared to conventional CP-OCT, our proposed PS-OCT could provide depth-resolved images, which reflect tissue birefringence.

A new approach for detection of leg movement using bio-impedance measurement

This paper describes the possibility of analyzing gait pattern from the variation of the lower leg electrical impedance. This impedance is measured by the four-electrode method. Two current electrodes are applied to the thigh, knee, and foot, and two potential electrodes are applied to the lateral aspect, medial aspect, and posterior position of lower leg. The correlation coefficients of the joint angle and the impedance change from human leg movement was obtained using electrogoniometer and 4ch impedance measurement system developed in this study. We found the optimal electrode position for ankle, knee and hip joint movements based on high correlation coefficient, least interference, and maximum magnitude of impedance change. The correlation coefficients of the ankle, knee, and the hip movements -0.87, 0.957 and 0.80, respectively. From such features of the lower leg impedance, it has been made clear that different movement patterns exhibit different impedance patterns and impedance level. This system showed possibility that lower leg movement could be easily measured by impedance measurement system with a few skin-electrodes.

Classification of joint pathology using an acoustical analysis of knee joint sound

The purpose of this study is to evaluate and classify arthritic pathology using the acoustical analysis of knee sound. Six normal subjects and 11 patients with knee problem were enrolled and patients were divided into the 1st patient group needed an orthopeadic surgery because of the ruptured wounds of meniscus or ACL (anterior cruciate ligament) and 2nd patient group diagnosed as osteoarthritis. In sitting and standing position, subjects flexed and extended the knee joint, the sounds and angle of knee joint were collected. The results showed that the values of fundamental frequency, jitter and shimmer of osteoarthritis patient group were larger than values of normal group and the values of orthopaedic patient group were smaller than values of normal group. These results suggest that an analysis of knee joint sound might assist non-invasive diagnosis of an articular pathology.