Method for Detecting Ventricular Activity of ECG Using Adaptive Threshold

Lee, S. H.,Yoon, Y. R. WALTER H CHANG 2016 Journal of medical and biological engineering Vol.36 No.3

<P>The QRS complex in an electrocardiogram reflects the activity of the cardiac ventricles. Cardiac ventricle activity can provide information about ventricular arrhythmia. This study investigated whether the dominant activity of the ventricles can be used to analyze ventricular arrhythmia characteristics. To assess ventricular activity, we modified the adaptive threshold method proposed by Shin et al. and developed a ventricular activity segmentation approach. The proposed method was tested using five cardiac episodes, namely normal sinus rhythm, supraventricular tachycardia, ventricular tachycardia, ventricular flutter, and ventricular fibrillation, obtained from the MIT-BIH and Creighton University Ventricular Tachyarrhythmia databases. The average sensitivity was 95.77 %, the average positive predictivity was 98.09 %, and the average failed detection rate was 6.08 %.</P>

Feasibility Study of Extracorporeal Shock Wave Lithotripsy for Chronic Total Occlusion Therapy

Jin, Z.,Choi, H.,Park, J.,Jung, C.,Ko, S. Y.,Park, J. O.,Park, S. WALTER H CHANG 2016 Journal of medical and biological engineering Vol.36 No.2

<P>Recently, due to a lack of exercise and aging, cardiovascular disease has become a major cause of death worldwide. Drug therapy and surgical operation have been widely used to treat cardiovascular disease. However, the treatment of chronic total occlusions (CTOs) through clinical operation still remains a considerable challenge, as CTOs have stiff proximal fibrous caps on their ends, which can be a serious barrier for a conventional operation using guide wires or biomedical devices. Through the analysis of the composition and physical properties of CTOs, we synthesized an artificial CTO composition consisting of collagen, blood, CaCO3, and levo-polylactic acid polymer. The artificial CTO composition was inserted into an arterial segment of swine, and a final CTO artery model was obtained. For the feasibility test of an extracorporeal shock wave lithotripsy (ESWL) device for CTO therapy, we adopted ESWL equipment with a C-arm X-ray fluoroscope. Through the feasibility tests, the optimal parameters of the ESWL equipment were found: an energy level of 4 (16.7-17.2 kV) and a total of 1000 shock waves. A tunneling efficiency of 85 % was achieved with the optimal parameters. We also tested the tunneling efficiency according to increased tissue thickness with the optimal parameters; the tunneling efficiency was reduced when the tissue thickness was increased, but the tunneling efficiency remained at 62 % for a tissue thickness of 3 cm. In addition, the final remaining clot ranged in size from 3 to 183 mu m, which was observed using a Nikon Ti-U microscope and analyzed using ImageJ. The safety of ESWL treatment was also confirmed through pathological analysis. Consequently, we expect that ESWL might become an effective therapeutic method for the tunneling of CTO.</P>

Maneuverable Capsule Endoscope Based on Gimbaled Ducted-Fan System: Concept and Simulation Results

Kim, M.,Lee, C.,Lee, Y.,Park, C.,Kim, Y.,Kim, S. WALTER H CHANG 2016 Journal of medical and biological engineering Vol.36 No.1

<P>Wireless capsule endoscopes are a growing research area because they can be easily swallowed by patients to capture images of the digestive system without pain. However, a drawback of current capsule endoscopes is that most use passive motion. To overcome this drawback, a maneuverable capsule endoscope (MCE) based on a gimbaled ducted-fan (GDF) system is proposed in this study. The system design, prototype development of the GDF system, and associated modeling and simulation are presented. The concept of the GDF is adopted from the thrust-vector control algorithm of a space shuttle. To prevent organ damage, the ducted fan, which generates and controls the thrust required for achieving maneuverability, is mounted on a gimbal structure. A scaled-up prototype of the GDF system was manufactured. The overall conceptual design of the MCE based on the GDF system is presented. A flow simulation and a three-dimensional path-following simulation are performed to evaluate the proposed MCE's applicability. The mean terminal velocity of the 6:1 scaled-up MCE prototype was calculated from flow simulation to be 0.6047, 0.5941, and 0.9204 m/s for the three postures of the GDF system, respectively, which represented the three translational degrees of freedom. For the 1:1 scale prototype, the mean terminal velocity was calculated to be 0.1147, 0.1127, and 0.1746 m/s for the above three postures, respectively. The proposed MCE dynamic model follows the desired path profile when the Lyapunov stability-based path-following algorithm was applied to it. In summary, the terminal velocity achieved in this research is sufficient for maneuvering inside the stomach organ. The results show that the MCE concept could be used for detecting and diagnosing abnormalities in the digestive system.</P>

Effect of Acoustic Properties of Lens Materials on Performance of Capacitive Micromachined Ultrasonic Transducers

Kim, S. H.,Chang, J. H. WALTER H CHANG 2016 Journal of medical and biological engineering Vol.36 No.4

<P>The acoustic lens in capacitive micromachined ultrasonic transducers (cMUTs) is pivotal not only for elevation focusing but also for insulation from high DC bias voltages. The selection of the lens material is crucial for realizing the full potential of a cMUT; in particular, the acoustic impedance, frequency-dependent attenuation, and shear velocity of the lens materials should be closely considered during the material selection process. By using the finite element method, we determined the effects of these acoustic properties on cMUT performance in terms of signal strength, center frequency, and spectral bandwidth. From the simulation results, it was found that acoustic impedance does not considerably influence cMUT performance if the acoustic impedance value ranges from 1.3 to 1.6 MRayl, which is similar to that of human tissue. However, both frequency-dependent attenuation and shear velocity cause a downshift in center frequency, a reduction in bandwidth, and a decrease in signal strength, which are the main factors leading to deterioration in the spatial resolution and signal-to-noise ratio of an ultrasound image.</P>

Biomechanical Evaluation of Dynamic Balance Control Ability During Golf Swing

Choi, A.,Kang, T. G.,Mun, J. H. WALTER H CHANG 2016 Journal of medical and biological engineering Vol.36 No.3

<P>Balance ability seems to be significantly correlated with golfing skill. However, it is unclear whether dynamic balance control has a direct influence on golf swing performance. In this study, the effects of a golfer's skill level on the observed dynamic balance control ability during the golf swing were evaluated. Fifty participants were divided into three groups (professional, advanced, and novice) based on their official handicap scores. Six infrared cameras and two force platforms were used to determine dynamic alterations of the center of mass (COM) and center of pressure (COP). The peak-to-peak displacement and velocity of the COM and COP in the professional golfers were generally lower than those of the other golfers. However, the professional golfers displayed significantly greater COM displacement than that of the advanced amateur golfers in the lead/trail direction (p < 0.01). This does not directly imply deterioration of the dynamic balance ability since the COM-COP separation decreased as the skill level of the golfers increased. The professional golfers had superior dynamic balance ability, achieved by controlling the COP excursion to compensate for the increased variation of COM, leading to a more stable swing mechanism than that of the amateur golfers. This study provides quantitative information for the evaluation of dynamic balance control during the golf swing.</P>