Woong Huh

Development of a video‐guided real‐time patient motion monitoring system

PURPOSE The authors developed a video image-guided real-time patient motion monitoring (VGRPM) system using PC-cams, and its clinical utility was evaluated using a motion phantom. METHODS The VGRPM system has three components: (1) an image acquisition device consisting of two PC-cams, (2) a main control computer with a radiation signal controller and warning system, and (3) patient motion analysis software developed in-house. The intelligent patient motion monitoring system was designed for synchronization with a beam on/off trigger signal in order to limit operation to during treatment time only and to enable system automation. During each treatment session, an initial image of the patient is acquired as soon as radiation starts and is compared with subsequent live images, which can be acquired at up to 30 fps by the real-time frame difference-based analysis software. When the error range exceeds the set criteria (δ(movement)) due to patient movement, a warning message is generated in the form of light and sound. The described procedure repeats automatically for each patient. A motion phantom, which operates by moving a distance of 0.1, 0.2, 0.3, 0.5, and 1.0 cm for 1 and 2 s, respectively, was used to evaluate the system performance. The authors measured optimal δ(movement) for clinical use, the minimum distance that can be detected with this system, and the response time of the whole system using a video analysis technique. The stability of the system in a linear accelerator unit was evaluated for a period of 6 months. RESULTS As a result of the moving phantom test, the δ(movement) for detection of all simulated phantom motion except the 0.1 cm movement was determined to be 0.2% of total number of pixels in the initial image. The system can detect phantom motion as small as 0.2 cm. The measured response time from the detection of phantom movement to generation of the warning signal was 0.1 s. No significant functional disorder of the system was observed during the testing period. CONCLUSIONS The VGRPM system has a convenient design, which synchronizes initiation of the analysis with a beam on/off signal from the treatment machine and may contribute to a reduction in treatment error due to patient motion and increase the accuracy of treatment dose delivery.

A biomedical signal segmentation algorithm for event detection based on slope tracing

In this paper a simple signal segmentation algorithm is introduced. The algorithm determines the epochs of signal components of interest based on signal characteristic such as amplitude, slope, deflection width, or distance between neighboring deflections. The epochs are segmented indirectly by means of a slope trace wave that traces a signal with its average slope and predetermined delay. The algorithm is applied to ECG and electrogram to show its practical applicability and efficiency. It is found that the algorithm can be used to choose particular signal components appropriately without significant signal preprocessing or complexity.

Automated keyword extraction using category correlation of data

In this paper, we proposed a system that extracts keywords using thesaurus which contains data saved by category. The system enhances precision of extracted keywords based on considering correlation of the category. 30 Living Modified Organisms related experimental documents were used in order for performance measurement of the system. The proposed system showed better precision than frequency-based system by 47 % and thesaurus-based system by 18 %.

An ECG signal processing algorithm based on removal of wave deflections in time domain

This paper introduces a new approach to process biomedical signals by surgically removing wave deflections in time domain. The method first determines the epochs of high frequency deflections, cuts out them from the signal, and then connects the two disconnected points. To determine the epoch of a deflection to be removed, four slope trace waves are used to isolate the deflection based on signal characteristics of amplitude, slope, duration, and distance from neighboring deflections. The method has been applied to simulated data and MIT-BIH arrhythmia database to show its practical efficacy in the case of baseline wandering removal. It is found that the method has the capability to identify and remove high frequency deflections appropriately, leaving low frequency deflection such as baseline drifting.

An event detection algorithm in ECG with 60Hz interference and baseline wandering

In this paper, a morphology based, time domain algorithm to detect QRS complexes in unfiltered ECG contaminated by 60Hz interference and baseline wandering is introduced. The method uses two slope trace waves which are the delayed version of an original signal with averaged slopes within a certain time interval. After the two slope trace waves are determined and used to remove 60Hz interference, another slope trace wave is followed to determine the epoch of QRS complexes by the help of amplitude and interval thresholds. The algorithm has been applied to ECG before preprocessing to show its practical applicability and efficiency. It is found that the method can detect the QRS complex appropriately in presence of 60Hz interference and baseline wandering.

A pacemaker sensing algorithm for low amplitude p-wave detection

A pacemaker sensing algorithm is devised for p-wave detection in low SNR atrial electrograms. The algorithm uses three parameters, amplitude, slew rate, and p-p interval, and a fuzzy neural network structure is adopted to combine their characteristics. The signal characteristic of the current event is compared to those of three most recent p-waves, and the similarity and dissimilarity between them are used to determine if the event is a p-wave. In addition, the distributions of the characteristics of recent p-waves are considered such that a wider distribution takes a less synaptic weight.

Development of pulse rate detection system for oriental medicine

The authors devised a pulse rate detection system to provide basic clinical index of cold-hot diagnosis of oriental medicine. The system consists of pulse signal detection, respiration signal detection, electrocardiograph detection, A/D conversion and computer system parts. The pulse rate, inspiration pulse rate and expiration pulse rate are defined as a pulse count in a respiration period, inspiration period and expiration period respectively. The clinical experiments on a normal person to evaluate the pulse rate detection system show a pulse/respiration ratio of 4.30/spl plusmn/1.03, a pulse/inspiration ratio of 1.60/spl plusmn/0.32, and a pulse/expiration ratio of 2.37/spl plusmn/0.75.

Behavior of an automatic pacemaker sensing algorithm for single-pass VDD atrial electrograms

Single-pass VDD pacemakers have been used as a result of simple implantation procedures and generally reliable atrial tracking. However, there is a controversy over their reliabilities of atrial tracking. As a new sensing method for reliable atrial tracking, a simple automatic pacemaker sensing, algorithm was implemented and evaluated to validate its benefits in sensing depolarization waves of single-pass VDD atrial electrograms. The automatic sensing algorithm had a predetermined sensing dynamic range and the sensitivity level was controlled as 50% of the average of two most recently sensed intrinsic amplitudes. The behavior of the automatic sensing algorithm in the single-pass VDD atrial electrograms was analyzed and characterized. It was observed that the automatic sensing algorithm was more effective than a conventional fixed threshold method to accurately detect and track p-waves in SVDD electrograms.

A light scattering cuvette for the measurement of thromboemboli type in flowing whole blood

A recent light scattering cuvette has been successful in differentiating the type of microemboli in flowing whole blood. However, since the technique was designed assuming the microemboli are concentrated near the center of the scattering medium, it is necessary to investigate the effect of off-center locations on discrimination. The scattering intensities from 5 off-center locations were investigated and the type discrimination parameter (ratio of two forward scattering intensities) was calculated. The perturbation solution of radiative transport equation was used to describe the scattered intensity distribution in the scattering medium. In each location the parameter used for discrimination was not significantly altered since the overall cuvette geometry compensates for the scattered intensity variation caused by off-center locations. Therefore, the scattering cuvette is reliable for differentiation of microemboli type.

Basic study on characterization of optical reflectance for the urine test paper

For semi-quantitative measurement of reflected light from the 8 way urine test paper, a prototype of urine monitoring system was designed. The system hardware was based on one-chip microcontroller, and its peripherals which consisted of ND converter, RAM, EPROM, LCD display and miniprinter. During analysis, the urine test paper was illuminated by LED lamp whose axes were at the angle of 45 degree and the light reflected vertically from the reagent area passed to the light detector. The reference and sample signal was converted by a microcontroller to a ratio and printed a semiquantitative value using a calibration line. INTRODUCTION Traditional wet chemistry has generally been performed by using some sort of glass or quartz container within which solutions are placed, both for seperated reaction steps and also for a possible analysis which may be spectroscopic in nature[r,2]. But dry test papers were incorporated all reagent within a single solid matrix such as paper or thin film or fiber. A chemical reaction will occur after sample has been applied to a reagent paper and change a color in a reagent area and then detected reflected light(3,4]. In order to demonstrate the capabilities of this instrument, pH and Occult-Blood assay were tested. We used the 8 way urine test paper. SYSTEM DESCRPTION The block diagram of urine test paper was shown in figure 1. Urine test paper was contained in paper cassette. The monitoring system was used three different LED(green, orange, red ) of high luminance and selected LED of each assay in current to voltage converter 0-7803-1377-1/93