Yoshiharu Sukenobu

Comparison of two methods for accurate measurement of modulation transfer functions of screen‐film systems

The modulation transfer function (MTF) of a screen-film system can be measured by two methods, i.e., a slit method with Fourier transform on the line spread function and a square-wave response function (SWRF) method. However, it is still uncertain whether MTFs obtained by the two methods are identical. In this study, MTFs of relatively sharp and unsharp screen-film systems were measured by using the two methods. The slit method provided slightly greater MTF for the relatively sharp system than the SWRF method. However, MTFs of the unsharp system obtained with the two methods were comparable. Generally, the slit method tends to provide reliable results for unsharp systems, whereas the SWRF method is favorable for sharp systems. Accuracy and consistency of these measurements were examined by comparison of experimental and theoretical edge responses derived from the measured MTFs. However, the difference in edge responses obtained by the two methods was relatively small compared with the variation of the measured edge responses, and thus results were considered inconclusive as to whether either of the methods can provide more accurate MTFs. International interlaboratory comparison indicated that the variation in the measured MTFs at six different institutions was relatively large for both methods. However, the MTFs of two screen-film systems measured by the slit method appear to agree with those by the SWRF method within the variation expected from the interlaboratory comparison.

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.

Evaluation of an asymmetric screen‐film system for chest radiography

To evaluate the potential utility of an asymmetric screen‐film system for chest radiography, its image quality and detail visibility compared with a conventional screen‐film system are investigated. The basic imaging properties were evaluated by measuring Hurter and Driffield curves, resolution properties, and noise Wiener spectra. The visibility of simulated anatomical and pathological details in radiographs of a chest phantom and normal anatomy in chest radiographs of patients were evaluated subjectively. The dynamic range of each system is comparable, though the asymmetric screen‐film system can provide an advantage over the conventional system due to a relative dose reduction of approximately 35% and higher resolution properties at high optical densities. The noise level of the asymmetric screen‐film system is slightly greater at low optical densities and much greater at high optical densities. However, the visibility of lung details with the asymmetric screen‐film system is slightly superior to the conventional screen‐film system despite the increase in noise. Mediastinal and retrodiaphragmatic details are similar, though marginally superior with the asymmetric screen‐film system. It is concluded that the asymmetric screen‐film system provided slightly superior image quality to the conventional screen‐film system for chest radiography, provided the average lung density is maintained at a higher level than is customary with conventional systems.

HIS:RIS contribution to image diagnosis and maximization of efficacy of PACS when coupled with HIS:RIS

To maximize the efficacy of the PACS coupled with the HIS/RIS and to clarify the effectiveness of the PACS itself, the amount of contribution of the HIS/NS to image diagnosis was measured beforehand. Video-tape recorders were used to record the CRT display of the HIS/RIS terminals and the simultaneous conversation between a patient and his physician in the clinics of our hospital. Consultation time and entry time for image examination order were measured for each case by replay of the tape. Consultation time was approximately 10 min, while order time was 2-3.5 min depending on whether the physician was an internist or an orthopedist. Detailed description on an order was closely related to detailed reports. The HIS/RIS contributed to image diagnosis even before the PACS was coupled. Concrete methods of efficacy maximization of the PACS were pointed out by internists and orthopedists in terms of modalities, outpatient clinics and wards.

JJ1017 image examination order codes: standardized codes supplementary to DICOM for imaging modality, region, and direction

The DICOM standard includes non-image data information such as image study ordering data and performed procedure data, which are used for sharing information between HIS/RIS/PACS/modalities, which is essential for IHE. In order to bring such parts of the DICOM standard into force in Japan, a joint committee of JIRA and JAHIS (vendor associations) established JJ1017 management guideline. It specifies, for example, which items are legally required in Japan while remaining optional in the DICOM standard. Then, what should be used for the examination type, regional, and directional codes? Our investigation revealed that DICOM tables do not include items that are sufficiently detailed for use in Japan. This is because radiology departments (radiologists) in the US exercise greater discretion in image examination than in Japan, and the contents of orders from requesting physicians do not include the extra details used in Japan. Therefore, we have generated the JJ1017 code for these 3 codes for use based on the JJ1017 guidelines. The stem part of the JJ1017 code partially employs the DICOM codes in order to remain in line with the DICOM standard. JJ1017 codes are to be included not only in IHE-J specifications, also in Ministry recommendations of health data exchange.

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.

PACS in Japan and progress of technology assessment

The statistics of PACS installations in Japan and the progress of key technologies over the past 13 years (1985-98) are described. The total number of installations of more than 557 is comparable with that (517) of hospital information systems (HIS), because advanced electronic technologies have brought a rapid spread of PACS for these 13 years. Examples of large sized PACS in Japan are discussed and a method for integrating HIS and RIS (Radiological Information System) is described. Standardization activities on PACS in Japan such as image data transfer and filing are also introduced. A unique domestic standard in Japan for IS&C (Image Save and Carry) and electronic filing of medical images is presented. The realization of DICOM in Japan is also described. Technology assessment of PACS is discussed in terms of methods and the results of measurement. Examples in the Osaka University Hospital over 6 years (1992-98) are presented. In order to figure out the effectiveness of PACS itself, the HIS/RIS contribution to radiological examination and reporting was measured before PACS was implemented. The total aim of the whole system operation is to maximize the effectiveness of HIS/RIS/PACS integrated each other. The results of time study, character counting in radiological reports, network loading study and other measurements are employed to expand the size of PACS in Osaka University which has 20 terminals at present.

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.

JJ1017 committee report: image examination order codes--standardized codes for imaging modality, region, and direction with local expansion: an extension of DICOM.

The digital imaging and communications in medicine (DICOM) standard includes parts regarding nonimage data information, such as image study ordering data and performed procedure data, and is used for sharing information between HIS/RIS and modality systems, which is essential for IHE. To bring such parts of the DICOM standard into force in Japan, a joint committee of JIRA and JAHIS established the JJ1017 management guideline, specifying, for example, which items are legally required in Japan, while remaining optional in the DICOM standard. In Japan, the contents of orders from referring physicians for radiographic examinations include details of the examination. Such details are not used typically by referring physicians requesting radiographic examinations in the United States, because radiologists in the United States often determine the examination protocol. The DICOM standard has code tables for examination type, region, and direction for image examination orders. However, this investigation found that it does not include items that are detailed sufficiently for use in Japan, because of the above-mentioned reason. To overcome these drawbacks, we have generated the JJ1017 code for these 3 codes for use based on the JJ1017 guidelines. This report introduces the JJ1017 code. These codes (the study type codes in particular) must be expandable to keep up with technical advances in equipment. Expansion has 2 directions: width for covering more categories and depth for specifying the information in more detail (finer categories). The JJ1017 code takes these requirements into consideration and clearly distinguishes between the stem part as the common term and the expansion. The stem part of the JJ1017 code partially utilizes the DICOM codes to remain in line with the DICOM standard. This work is an example of how local requirements can be met by using the DICOM standard and extending it.

PACS with personal computer and workstation for HIS, RIS, PACS integration

Osaka University hospital moved to the new hospital in September 1993, where HIS and RIS are installed and a part of PACS will be installed to provide safe and convenient circumstances for patients and hospital staffs. We investigated the flow of radiological examination orders, X-ray films, and diagnostic reports in the previous film-based system, and estimated the data volume in digital PACS. We designed (1) the total hospital information system and PACS, (2) RIS, FCR and controller connection and (3) RIS, handy terminal and FCR connection.