Biomedical subjects

Sun K Yoo

Publications and source records attributed to Sun K Yoo.

12 recordsLinked to original sources

PubMed2006

Motion artifact reduction in photoplethysmography using independent component analysis.

Removing the motion artifacts from measured photoplethysmography (PPG) signals is one of the important issues to be tackled for the accurate measurement of arterial oxygen saturation during movement. In this paper, the motion artifacts were reduced by exploiting the quasi-periodicity of the PPG signal and the independence between the PPG and the motion artifact signals. The combination of independent component analysis and block interleaving with low-pass filtering can reduce the motion artifacts under the condition of general dual-wavelength measurement. Experiments with synthetic and real data were performed to demonstrate the efficacy of the proposed algorithm.

Algorithms↗

PubMed2006

Wavelet-based low-delay ECG compression algorithm for continuous ECG transmission.

The delay performance of compression algorithms is particularly important when time-critical data transmission is required. In this paper, we propose a wavelet-based electrocardiogram (ECG) compression algorithm with a low delay property for instantaneous, continuous ECG transmission suitable for telecardiology applications over a wireless network. The proposed algorithm reduces the frame size as much as possible to achieve a low delay, while maintaining reconstructed signal quality. To attain both low delay and high quality, it employs waveform partitioning, adaptive frame size adjustment, wavelet compression, flexible bit allocation, and header compression. The performances of the proposed algorithm in terms of reconstructed signal quality, processing delay, and error resilience were evaluated using the Massachusetts Institute of Technology University and Beth Israel Hospital (MIT-BIH) and Creighton University Ventricular Tachyarrhythmia (CU) databases and a code division multiple access-based simulation model with mobile channel noise.

Algorithms↗

PubMed2005

A Web-based mobile asthma management system.

Continuous recording of daily symptoms constitutes an effective means of managing asthma patients. Daily management reduces the costs associated with hospitalization and improves the quality of patient care. We have implemented a Web-based mobile asthma management system. We used a pocket PC, mobile phone and desktop computer. The recorded items and individualized prescriptions were structured using Extensible Mark-up Language (XML) DTD (Data Type Definition). The mobile Web form was automatically adjusted to fit the different display resolutions of the terminal devices. The system provided reliable exchange of all relevant information between a doctor and the asthma patient using wireless mobile transmission. E-mail and Short Messaging Service (SMS) were used to send messages to patients, for example in the case of an automatically determined patient alert. Patients could obtain customized instructions according to their daily personal symptoms, peak expiratory flow (PEF), medications and activity restriction. The daily graph of PEF and the graphs of symptoms and medication were particularly useful for asthma patient control and self-awareness of the progress of the disease.

Asthma↗

PubMed2005

Instant wireless transmission of radiological images using a personal digital assistant phone for emergency teleconsultation.

The instant transmission of radiological images may be important for making rapid clinical decisions about emergency patients. We have examined an instant image transfer system based on a personal digital assistant (PDA) phone with a built-in camera. Images displayed on a picture archiving and communication systems (PACS) monitor can be captured by the camera in the PDA phone directly. Images can then be transmitted from an emergency centre to a remote physician via a wireless high-bandwidth network (CDMA 1 x EVDO). We reviewed the radiological lesions in 10 normal and 10 abnormal cases produced by modalities such as computerized tomography (CT), magnetic resonance (MR) and digital angiography. The images were of 24-bit depth and 1,144 x 880, 1,120 x 840, 1,024 x 768, 800 x 600, 640 x 480 and 320 x 240 pixels. Three neurosurgeons found that for satisfactory remote consultation a minimum size of 640 x 480 pixels was required for CT and MR images and 1,024 x 768 pixels for angiography images. Although higher resolution produced higher clinical satisfaction, it also required more transmission time. At the limited bandwidth employed, higher resolutions could not be justified.

Cell Phone↗

PubMed2004

Real-time emergency telemedicine system: prototype design and functional evaluation.

In this paper, an emergency telemedicine system was designed for the transmission of real-time multimedia for remote consultation, including radiological images, patient records, video-conferencing, full-quality video, ECG, BP, respiration, temperature, SpO(2), systolic and diastolic pressures and heart rate. The standardized, modular, software-based design architecture, without resorting to external hardware compression boards, enables the low-cost implementation of the telemedicine system, using the unified, systematic and compact integration of multimedia on general personal computers. Experimental tests on local networks analyze the technical aspects of designed systems, and inter-hospital experiments demonstrate its clinical usefulness.

Computer Systems↗

PubMed2004

Three-dimensional localization of cochlear implant electrodes using epipolar stereophotogrammetry.

Three-dimensional (3-D) localization of individual cochlear implant electrodes within the inner ear is of importance for modeling the electrical field of the cochlea, designing the electrode array, and programming the associated speech processor. A 3-D reconstruction method of cochlear implant electrodes is proposed to localize individual electrodes from two X-ray views in combination with the spiral computed tomography technique. By adapting epipolar geometry to the configuration of an X-ray imaging system, we estimate individual electrode locations in the least square sense without using a patient attachment required by an existing stereophotogrammetry technique. Furthermore, our method does not require any knowledge of the intrinsic and extrinsic parameters of the imaging system. The performance of our method is studied in numerical simulation and with patient data and is found to be sufficiently accurate for clinical use. The maximum root mean-square errors measured are 0.0445 and 0.214 mm for numerical simulation and patient data, respectively.

Cochlea↗

PubMed2004

Evaluation of compressed video-images for emergency telemedicine work with trauma patients.

Video-encoders in telemedicine systems need to adjust their coding methods for operation on heterogeneous networks on which bandwidth fluctuates. We evaluated MPEG-4 compressed video-pictures of three trauma patients. We compared the original video-frames with compressed video-frames in terms of the peak signal-to-noise ratio (PSNR). In a qualitative evaluation, three emergency specialists scored the quality of the video-images blind, on a five-point scale (1= bad to 5 = excellent). The PSNR increased as the bit rate increased from 0.2 to 6 Mbit/s. When the bit rate was fixed, in other words at a given network bandwidth, a higher PSNR was obtained at the expense of spatial resolution and frame rate. The video quality was highly affected by the amount of camera shake. Emergency telemedicine systems require a high bit rate, high spatial resolution and a high frame rate to achieve optimum video quality. However, if the bandwidth is limited (i.e. the bit rate is fixed), temporal resolution becomes more important than spatial resolution.

Data Compression↗

PubMed2004

Performance of a web-based, realtime, tele-ultrasound consultation system over high-speed commercial telecommunication lines.

A Web-based, realtime, tele-ultrasound consultation system was designed. The system employed ActiveX control, MPEG-4 coding of full-resolution ultrasound video (640 x 480 pixels at 30 frames/s) and H.320 videoconferencing. It could be used via a Web browser. The system was evaluated over three types of commercial line: a cable connection, ADSL and VDSL. Three radiologists assessed the quality of compressed and uncompressed ultrasound video-sequences from 16 cases (10 abnormal livers, four abnormal kidneys and two abnormal gallbladders). The radiologists' scores showed that, at a given frame rate, increasing the bit rate was associated with increasing quality; however, at a certain threshold bit rate the quality did not increase significantly. The peak signal to noise ratio (PSNR) was also measured between the compressed and uncompressed images. In most cases, the PSNR increased as the bit rate increased, and increased as the number of dropped frames increased. There was a threshold bit rate, at a given frame rate, at which the PSNR did not improve significantly. Taking into account both sets of threshold values, a bit rate of more than 0.6 Mbit/s, at 30 frames/s, is suggested as the threshold for the maintenance of diagnostic image quality.

Data Compression↗

PubMed2003

Alignment of CT images of skull dysmorphology using anatomy-based perpendicular axes.

Rigid body registration of 3D CT scans, based on manual identification of homologous landmarks, is useful for the visual analysis of skull dysmorphology. In this paper, a robust and simple alignment method was proposed to allow for the comparison of skull morphologies, within and between individuals with craniofacial anomalies, based on 3D CT scans, and the minimum number of anatomical landmarks, under rigidity and uniqueness constraints. Three perpendicular axes, extracted from anatomical landmarks, define the absolute coordinate system, through a rigid body transformation, to align multiple CT images for different patients and acquisition times. The accuracy of the alignment method depends on the accuracy of the localized landmarks and target points. The numerical simulation generalizes the accuracy requirements of the alignment method. Experiments using a human dried skull specimen, and ten sets of skull CT images (the pre- and post-operative CT scans of four plagiocephaly, and one fibrous dysplasia patients), demonstrated the feasibility of the technique in clinical practice.

Adolescent↗

PubMed2003

Polygon reduction of 3D objects using Stokes' theorem.

Surface over volume rendering can be useful for many applications. However, the tremendously large number of polygons composing the surface primitives should be reduced to a manageable size so as to utilize the capability of low cost hardware and software rendering engines, a standard Internet protocol and VRML format. In this paper, we propose a novel algorithm that deletes several vertices simultaneously by forming a closed arbitrary shaped boundary. The Stokes' theorem, used in electro-magnetic field analysis, was newly adapted to extract the arbitrary shaped boundary. The simultaneous deletion procedure provides a computational gain and increases the reduction ratio without sacrificing the topological distortion of the original mesh. Numerically synthesized polygonal objects and real CT data were tested to evaluate the performance of the new algorithm and to demonstrate the possibility of a medical rendering application. The new algorithm outperforms the conventional decimation algorithm in both computational and reduction efficiency.

Algorithms↗

PubMed2003

Evaluation of two mobile telemedicine systems in the emergency room.

Two different prototype mobile telemedicine systems were constructed for use in the emergency room. They could transmit physiological signals as well as video pictures and sound. One device, the mobile emergency bed (MEB), was powered by battery and had a wireless connection to the local-area network (LAN). For the other, the mobile emergency server (MES), a patient monitor, video-camera and microphone were connected by a radio-frequency link to a server. A functional evaluation and a clinical evaluation (by 12 emergency doctors in six emergency centres) were performed on both prototypes. The bandwidth and the video quality of the MEB were better than those of the MES, because of the digital transmission of the wireless LAN. The MES was better for directing patient treatment and teleconsultation; the MEB was better for static patients in the emergency centre. In general, the MES was more suitable for practical emergency telemedicine work.

Attitude of Health Personnel↗

PubMed2002

Improvement of multi-channel isolated bio-potential amplifiers using multiplexing.

We propose a simple isolated link circuit for a multi-channel bio-potential amplifier, by adapting the multiplexing/demultiplexing technique that is generally used in digital circuit design. The reduced number of isolation amplifiers, due to the multiplexing technique, results in an increase in the amount of isolation, as well as a reduction in manufacturing cost. The simple incorporation of a dead-zone in multiplexed timing, and a pull-down resistor in the multiplexed signal line, enables a multiple isolated bio-signal transmission over the shared isolation amplifier, with an affordable inter-channel cross talk.

Brain↗