Sun Kook Yoo

Clinical Evaluation of Compression Ratios using JPEG2000 on Computed Radiography Chest Images

The efficient compression of radiographic images is of importance for improved storage and network utilization in support of picture archiving and communication systems (PACS) applications. The DICOM Working Group 4 adopted JPEG2000 as an additional compression standard in Supplement 61 over the existing JPEG. The wavelet-based JPEG2000 can achieve higher compression ratios with less distortion than the Discrete Cosine Transform (DCT)-based JPEG algorithm. However, the degradation of JPEG2000-compressed computed radiography (CR) chest images has not been tested comprehensively clinically. The authors evaluated the diagnostic quality of JPEG2000-compressed CR chest images with compression ratios from 5:1 to 200:1. An ROC (receiver operating characteristic analysis) and t test were performed to ascertain clinical performance using the JPEG2000-compressed images. The authors found that compression ratios as high as 20:1 can be utilized without affecting lesion detectability. Significant differences between the original and the compressed CR images were not recognized up to compression ratio of 50:1 within a confidence level of 99%.

PDA–Phone-Based Instant Transmission of Radiological Images over a CDMA Network by Combining the PACS Screen with a Bluetooth-Interfaced Local Wireless Link

Remote teleconsultation by specialists is important for timely, correct, and specialized emergency surgical and medical decision making. In this paper, we designed a new personal digital assistant (PDA)–phone-based emergency teleradiology system by combining cellular communication with Bluetooth-interfaced local wireless links. The mobility and portability resulting from the use of PDAs and wireless communication can provide a more effective means of emergency teleconsultation without requiring the user to be limited to a fixed location. Moreover, it enables synchronized radiological image sharing between the attending physician in the emergency room and the remote specialist on picture archiving and communication system terminals without distorted image acquisition. To enable rapid and fine-quality radiological image transmission over a cellular network in a secure manner, progressive compression and security mechanisms have been incorporated. The proposed system is tested over a code division Multiple Access 1×-Evolution Data-Only network to evaluate the performance and to demonstrate the feasibility of this system in a real-world setting.

Neural network based emotion estimation using heart rate variability and skin resistance

In order to build a human-computer interface that is sensitive to a users expressed emotion, we propose a neural network based emotion estimation algorithm using heart rate variability (HRV) and galvanic skin response (GSR). In this study, a video clip method was used to elicit basic emotions from subjects while electrocardiogram (ECG) and GSR signals were measured. These signals reflect the influence of emotion on the autonomic nervous system (ANS). The extracted features that are emotion-specific characteristics from those signals are applied to an artificial neural network in order to recognize emotions from new signal collections. Results show that the proposed method is able to accurately distinguish a users emotion.

Integrated Solution for Physical Activity Monitoring Based on Mobile Phone and PC.

Objectives This study is part of the ongoing development of treatment methods for metabolic syndrome (MS) project, which involves monitoring daily physical activity. In this study, we have focused on detecting walking activity from subjects which includes many other physical activities such as standing, sitting, lying, walking, running, and falling. Specially, we implemented an integrated solution for various physical activities monitoring using a mobile phone and PC. Methods We put the iPod touch has built in a tri-axial accelerometer on the waist of the subjects, and measured change in acceleration signal according to change in ambulatory movement and physical activities. First, we developed of programs that are aware of step counts, velocity of walking, energy consumptions, and metabolic equivalents based on iPod. Second, we have developed the activity recognition program based on PC. iPod synchronization with PC to transmit measured data using iPhoneBrowser program. Using the implemented system, we analyzed change in acceleration signal according to the change of six activity patterns. Results We compared results of the step counting algorithm with different positions. The mean accuracy across these tests was 99.6 ± 0.61%, 99.1 ± 0.87% (right waist location, right pants pocket). Moreover, six activities recognition was performed using Fuzzy c means classification algorithm recognized over 98% accuracy. In addition we developed of programs that synchronization of data between PC and iPod for long-term physical activity monitoring. Conclusions This study will provide evidence on using mobile phone and PC for monitoring various activities in everyday life. The next step in our system will be addition of a standard value of various physical activities in everyday life such as household duties and a health guideline how to select and plan exercise considering ones physical characteristics and condition.

A Mobile Tele-Radiology Imaging System with JPEG2000 for an Emergency Care

The aim of this study was to design a tele-radiology imaging system for rapid emergency care via mobile networks and to assess the diagnostic feasibility of the Joint Photographic Experts Group 2000 (JPEG2000) radiological imaging using portable devices. Rapid patient information and image exchange is helpful to make clinical decisions. We assessed the usefulness of the mobile tele-radiology system by measuring both a quantitative method, PNSR calculation, for image qualities, and its transmission time via mobile networks in different mobile networks, respectively; code division multiple access evolution-data optimized, wireless broadband, and high-speed downlink packet access; and the feasibility of the JPEG2000 computed tomography (CT) images by qualitatively assessing with the Alberta stroke program early CT score method with 12 CT image cases (seven normal and five abnormal cases). We found that the quality of the JPEG2000 radiological images was satisfied quantitatively and was judged as acceptable qualitatively at 5:1 and 10:1 compression levels for the mobile tele-radiology imaging system. The JPEG2000-format radiological images achieved a fast transmission while maintaining a diagnosis quality on a portable device via mobile networks. Unfortunately, a PDA device, having a limited screen resolution, posed difficulties in reviewing the JPEG2000 images regardless of the compression levels. An ultra mobile PC was preferable to study the medical image. The mobile tele-radiology imaging systems supporting JPEG2000 image transmission can be applied to actual emergency care services under mobile computing environments.

Ubiquitous-severance hospital project: implementation and results.

Objectives The purpose of this study was to review an implementation of u-Severance information system with focus on electronic hospital records (EHR) and to suggest future improvements. Methods Clinical Data Repository (CDR) of u-Severance involved implementing electronic medical records (EMR) as the basis of EHR and the management of individual health records. EHR were implemented with service enhancements extending to the clinical decision support system (CDSS) and expanding the knowledge base for research with a repository for clinical data and medical care information. Results The EMR system of Yonsei University Health Systems (YUHS) consists of HP integrity superdome servers using MS SQL as a database management system and MS Windows as its operating system. Conclusions YUHS is a high-performing medical institution with regards to efficient management and customer satisfaction; however, after 5 years of implementation of u-Severance system, several limitations with regards to expandability and security have been identified.

Prototype design of mobile emergency telemedicine system

High bit rate wireless cellular service using CDMA 1X-EVDO is now popular in Korea, particularly in urban areas, since it was launched commercially in 2002. This cellular service allows the real-time transmission of patient images and vital sign signals simultaneously in a moving ambulance application. In this paper, we designed a prototype emergency telemedicine system that can transfer both biological signal and patient motion video from a moving vehicle using a CDMA 1X-EVDO reverse link. To cope with the limited bandwidth of the reverse link (transmission bandwidth of cellular device) relative to the the forward link (receiving bandwidth), priority control between the vital sign and video images, frame rate control using MPEG-4 compression, and error control using automatic repeat request were incorporated into the application layer protocol of the designed prototype system. Many on-road experiments have been performed to evaluate the actual performance and to demonstrate the applicability in a real situation. In most cases, the biological signal and patient video images with reduced frame rate were successfully transmitted from the moving vehicle in urban areas.

Development and evaluation of a CMOS sensor-based digital intra-oral radiographic system

As part of an ongoing investigation into the development of a dental digital radiographic (DDR) system using a complementary metal-oxide semiconductor (CMOS) sensor, this study developed hardware and software with a graphical user interface to acquire and display intra-oral images from a prototype DDR system. The aim of this study was to develop a DDR system using a CMOS sensor and evaluate its characteristics. Electrical signals that were generated by the CMOS sensor were transformed into digital images by a control computer equipped using a USB board. The distance between the X-ray tube and the CMOS sensor was adjusted within the range of 10-40 cm to provide the optimal image quality. In order to evaluate the image quality according to variations in the dose, phantom images (60 kVp, 7 mA) were obtained at exposure times of 0.03, 0.05, 0.08, 0.10, and 0.12 s, and the signal-to-noise ratio (SNR) was calculated from the phantom image data. The modulation transfer function (MTF) was obtained from a Fourier transform of the line spread function, which was itself derived from the edge spread function of a sharp edge image acquired using the exposure conditions of 60 kVp, 7 mA, and 0.08 s exposure time. The best contrast and focus were obtained at 20 cm. The SNR level was found to increase with increasing exposure time ranging from 0.03 to 0.08 s. The results obtained at 10% of the MTF showed that the resolution of the DDR system was approximately 6.2 line pairs per millimeter. The characteristics of the prototype DDR system have potential applications in intra-oral dental radiographic imaging. The fully developed DDR system can be used for making a clinical diagnosis with further improvements in the acquisition time and spatial resolution.

Migration of medical image data archived using mini-PACS to full-PACS.

This study evaluated the migration to full-PACS of medical image data archived using mini-PACS at two hospitals of the Yonsei University Medical Center, Seoul, Korea. A major concern in the migration of medical data is to match the image data from the mini-PACS with the hospital OCS (Ordered Communication System). Prior to carrying out the actual migration process, the principles, methods, and anticipated results for the migration with respect to both cost and effectiveness were evaluated. Migration gateway workstations were established and a migration software tool was developed. The actual migration process was performed based on the results of several migration simulations. Our conclusions were that a migration plan should be carefully prepared and tailored to the individual hospital environment because the server system, archive media, network, OCS, and policy for data management may be unique.

Analysis of the heart rate and its variation affecting image quality and optimized reconstruction window in retrospective ECG-gated coronary angiography using multidetector row CT

It is clinically important to examine the effect of the heart rate and its variation on the image quality and selection of the optimized window in coronary angiography using multidetector row CT (MDCT). This study performed contrast-enhanced coronary angiography using MDCT on 83 patients. Fifty-two cases with information on the heart rate available were enrolled in this study. The effect of heart rate and its variation were systemically analyzed. Two radiologists rated the image quality as follows: 4-excellent; 3-good; 2-fair; 1-bad. Cardiac cycle windows at 40% and 70% were routinely selected for image reconstruction. The optimized window was rated as 1 when a 40% reconstruction had a better quality than the 70% reconstruction, as 2 when the 40% reconstruction was the same as the 70% reconstruction, and as 3 when the 70% reconstruction was better than the 40% reconstruction. The image quality was more affected by a variation of the heart rate than by the high heart rate. The selection of the optimized reconstruction window for a good image quality was mostly affected by the heart rate and there was a tendency for the 40% phase reconstruction to have a better image quality than the 70% reconstruction at higher heart rates.It is clinically important to study the effect of heart rate and its variation on image quality, and selection of optimized window in coronary angiography using multi-detector row CT (MDCT). We performed contrast-enhanced coronary angiography using MDCT in 83 patients. Sixty cases with available information of heart rate were enrolled in this study. We systemically analyzed the effect of heart rate and its variation. Two radiologists rated image quality as follows: 4, excellent; 3, good; 2, fair; 1, bad. Cardiac cycle windows at 70 and 40% were routinely selected for image reconstruction. Both of 40% and 70% reconstructed images were available only to fifty-seven cases. Optimized window was rated as 1 when 40% reconstruction was better quality than 70%, as 2 when 40% reconstruction was the same as 70%, and as 3 when 70% reconstruction was better than 40%.