The Design of Wavelet-based Biological Signal CODEC for Telemedicine Application / 대한의료정보학회지

In this paper, waveform preserving coding technique is proposed for the bio-signals based on wavelet transform local maxima representation. In order to efficiently encode the bio-signal, it utilize the inherent property of bio-signals that sharp waves corresponding to the local maxima in wavelet domain contain the most of the clinically significant information in general. The testing sets of ECG and EEG are experimented to select the appropriate wavelet basis and to demonstrate the usefulness regarding to coding efficiency. The spline basis is more suitable in designing the coder than the Harr basis since the spline basis produces less number of local maxima than the Harr basis. The proposed wavelet method based on spline basis outperforms the conventional subband coding technique in terms of wave form degradation and coding efficiency. The actual transmission experiment using external communication network and the general personal computer demonstrates the applicability to telemedicine system handling the bio-signals.

Spectral analysis of heart valve sound for detection of prosthetic heart valve diseases

The spectral analysis of heart valve sound is a noninvasive diagnostic method known to be useful in evaluating the state of the heart valve function. This may provide early detection of valve calcification, thrombus or destruction, since previous studies have shown that the dominant frequency peak moved to a high frequency area when natural heart valve leaflets were calcified, stiffened or destroyed. However, it is important for a heart valve sound diagnostic system to find a proper spectral analysis method on phonocardiography. Until now, conventional frequency analyses such as the Fourier transform or autoregressive spectral estimation technique have been used to estimate spectral components of a phonocardiogram, but they are inappropriate because the signal frequency is assumed to remain constant during the transform interval. To overcome this problem, in this study, FOS (Fast Orthogonal Search) & MUSIC (MUltiple SIgnal Classification), which both appeared suitable for the analysis of biological data, were applied to prosthetic heart valve sound as the new heart valve sound spectral analysis methods. Five subjects with normally functioning mechanical heart valves and a patient with a malfunctioning one were selected to collect the heart valve sound signals. As a result, the second dominant peak frequency proved to be important along with the first dominant peak frequency in identifying the valve function. This study showed that the new heart valve sound spectral analysis method presented in this paper may be an effective method in heart valve sound analysis. Further study using this system in a large population of patients will aid in providing a diagnostic method in the early detection of valve failure.

Design of a medical image processing software for clinical-PACS

Software modules for interactive display, manipulation and retrieval of medical images have been designed for a Picture Archiving and Communications System (PACS). The target of these modules is not for a high-end diagnostic workstation for radiologists, but for a PC-based low cost clinical workstation for a referring physician. This software is constructed based on a concept of an object-oriented language which is designed to be modular and expandable. It consists of several functional modules: (a) a communication module for image retrieval, (b) a standard module for the interpretation of the DICOM images, (c) a user interface module for the non-computer oriented clinicians and (d) a tool module for viewing and manipulating images as well as editing the annotation.

In vitro sound spectral analysis of prosthetic heart valves by mock circulatory system

A comparative study was made of the sounds produced by normal prosthetic valves (St. Jude Medical, Bjork-Shiley, polymer) with those produced by the same valves but having simulated thrombosis at the stent, hinge, or strut. Comparisons of the closing sound were made for the power frequency spectra associated with individual valves. We used periodogram approach to obtain the spectral characteristics of the valve prostheses. The closing sound of the abnormal mechanical valves displayed lower apparent peak frequency. But the abnormal polymer valve produced higher apparent peak frequency. The results showed that frequency spectra gave information pertinent to the simulated malfunction. Sound spectral analysis is believed to be a simple and a good diagnostic tool for detection of prosthetic valve malfunction. Also it seemed to be superior to other methods such as phonocardiography and echocardiography.