Yasuhiko Okura

PACS development in Asia

First, history of PACS in Japan from 1982 to 2002 has been investigated. By 2002 total of 1468 PACS units have been installed. Of these, 1174 are small-size PACS with less than four image display terminals, 203 are medium-size with 5-14 terminals, and 91 are large-size with 15 up to 1300 terminals. The main nine large-size PACS of 91 have been retrospectively investigated from 1984 for PACS experiments and from 1989 for PACS operation. Most of these nine hospitals have increased the number of PACS terminals by installing additional PACS units, instead of reinforcing the existing single PACS. The use of DICOM interfaces has increased the number of modalities connected to PACS and influenced the spreading of PACS installations in Japan. The status of HIS and RIS coupling to PACS, and the use of PACS in primary diagnosis or in image referral are discussed. Assessment of PACS is now in an early stage. Baseline studies of HIS/RIS/PACS effectiveness have been carried out to assess quantitatively the PACS merit. Second, history of PACS development in Korea is described. Very acute climbing up of filmless PACS diffusion was observed from 2000 to 2002. The reasons seem to be lack of domestic X-ray film industry, economic crisis in 1997 and PACS Reimbursement Act in health insurance in Korea. Third, the Hong Kong Wide Area Image Distribution/PACS Project is reported. It is now under phase 1 of design and partial implementation employing the latest and the highest ends of advanced technology such as failure resilience.

An Inductive Method for Automatic Generation of Referring Physician Prefetch Rules for PACS

To prefetch images in a hospital-wide picture archiving and communication system (PACS), a rule must be devised to permit accurate selection of examinations in which a patients images are stored. We developed an inductive method to compose prefetch rules from practical data which were obtained in a hospital using a decision tree algorithm. Our methods were evaluated on data acquired in Osaka University Hospital for one month. The data collected consisted of 58,617 cases of consultation reservations, 643,797 examination histories of patients, and 323,993 records of image requests in PACS. Four parameters indicating whether the images of the patient were requested or not for each consultation reservation were derived from the database. As a result, the successful selection sensitivity for consultations in which images were requested was approximately 0.8, and the specificity for excluding consultations accurately where images were not requested was approximately 0.7.

Evaluation of the Effect of Varying MPEG-2 Compression Ratios on Digital Coronary Angiographic Assessment of Stenosis Severity

The purpose of this study is to evaluate the influence of MPEG-2 compression scheme on coronary angiography and to search the highest compression ratio at which no significant effect to accuracy of assessment of stenosis severity occurs. Forty-Four digital cine angiographies were used. Three cardiologists participated in a subjective study in which they read both uncompressed images and compressed images. Furthermore, an objective study was carried out to measure vessel stenosis ratio by using software. The influence of compression was evaluated by kappa statistics in case of subjective study and by both systematic error and random error in case of objective study. Kappa statistics between uncompressed image and compressed image at a ratio of 80:1 was significantly lower than that of other compression ratios such as 40:1. Similar results were obtained in objective evaluation. In this report, the authors provide the baseline for further studies on observer performance for motion images.

Generalization of methodology of measurement for clinical evaluation of HIS/RIS

To establish generalized method of quantitative measurement of clinical effectiveness of HIS/RIS, a method of comparison between pre/post operation of a system and between different systems operated in different hospitals was proposed. A generalized method for calculation of effectiveness index by score functions was developed. The results of measurement and calculation were applied to look for the timing of version up of the systems and also will be applied to grasp the effectiveness of revised systems. We have measured clinical effectiveness quantitatively along the method of technology assessment of HIS/RIS in Osaka University since 1993. Objects of measurement in HIS were time study such as consulting time, machine operation time, machine operation time with conversation between a physician and his patient and so on. And objects of measurement in RIS were reporting time for image diagnosis, writing time for a report and number of characters written in a radiological report and so on. Actual numerical value of index was calculated according to the developed score function and variables measured in 1998 and 1999 for HIS, and also according to the score function and variables measured in 1993 before RIS operation and after RIS operation in 1994, 1995, 1996, 1998 and 1999. The measurement and calculation will be carried out in other hospitals at large and the indices will be compared between hospitals in terms of system characteristics.

Development of remote surgical navigation and biopsy needle guidance system using Open-MRI and high-speed network

This study describes a remote surgical guidance and navigation system developed for surgery using “Open-MRI” and high-speed network. We connected Osaka University Hospital and Kawasaki Hospital which has deployed Open- MRI with high speed IP over ATM network. The distance between two hospitals is approximately 50 km. Two video cameras were installed with an angle of 40 degrees on an open-MRI gantry to obtain intraoperative images. Two pairs of CODEC (AD/DA converter) were equipped on the network to transfer both images and sound in real time. A pointer system to indicate a region on an image was also developed. MRI images obtained by Open-MRI were transferred to a 3D workstation in Osaka University Hospital. The system was designed for a senior surgeon in Osaka University to advise regarding accurate needle direction for a remote patient by checking the reconstructed 3D images and schemata shown by the navigation software. The schemata were also superimposed on intraoperative images from two cameras, and the superimposed images were sent back to Kawasaki Hospital. This system allowed a surgeon in the operation room at Kawasaki Hospital to accurately view navigation schema under supervision by a senior surgeon in a remote university hospital with superimposion of intraoperative images. The pointer system allowed both doctors to share intraoperative images during a virtual-real surgical operation. A successful biopsy case using this newly developed system illustrates the effectiveness of this system.

Time study of computer aided diagnosis—a preliminary results on temporal subtraction

Abstract In this paper, we present the results of time study of CAD (Computer-Aided Diagnosis) on temporal subtraction for ground-glass shadow on chest radiographs. Our results showed that the average reading time with the CAD system was significantly longer than without employing the CAD system. However, diagnostic accuracy with temporal subtraction images was slightly improved than without temporal subtraction (with; Az=0.96, without; Az=0.95). Consequently, we could interpret that the radiologists performance was enhanced by CAD on temporal subtraction, even with longer reading time.

A modeling of PACS performance and simulation using stochastic activity network for optimized design

To evaluate PACS performance, simulation model of PACS performance employing PetriNet was developed and the simulation was carried out. Variables used in the simulation were measured in Osaka University Hospital. The authors developed model for three connection types of Image Display Terminal (IDT) and servers. From results, the authors found that Type I is optimized design of PACS with the shortest response time among three types.