(Radiographics. 2000;20:573-580.)
© RSNA, 2000
Development of an Electronic Radiologist's Office in a Private Institute1
Jean-Chrétien Oberson, MD ,
Ronald Welz, PhD and
Laurent Bovisi, PhD
1 From the Centre d'Imagerie Diagnostique, Grand-Chêne 8 bis, CH-1003 Lausanne, Switzerland (J.C.O.); and WDS Technologies, Geneva, Switzerland (R.W., L.B.). Presented as an infoRAD exhibit at the 1998 RSNA scientific assembly. Received February 16, 1999; revision requested April 13; final revision received September 14; accepted September 23. Address reprint requests to J.C.O. (e-mail: cid@worldcom.ch).
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Abstract
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A computer system that improves the quality, user-friendliness, accessibility, and management of radiology data (images, reports, databases, knowledge) was implemented at a private institute. A picture archiving and communication system (PACS) was integrated with the radiology information system (RIS). Two servers and 12 personal computers form the integrated system. The first server is dedicated to management and archiving of Digital Imaging and Communications in Medicine (DICOM) images. The second server is dedicated to management of the RIS and archiving of patient data (Structured Query Language database), reports (hypertext markup language [HTML]), and images in the Joint Photographic Experts Group (JPEG) format (mini-PACS). There are three main client-server networks: a common network of imaging modalities (magnetic resonance imaging, computed tomography, ultrasonography, digital radiography) and two fast Ethernet networks (the PACS network and the RIS network). The RIS-PACS is linked remotely with other workstations and servers via Integrated Services Digital Network (ISDN). Images and reports can be distributed to referring physicians in the form of multimedia HTML and JPEG documents, which can also be used for quick and easy archiving, distribution, and reviewing within the institute. However, referring physicians have been reluctant to use electronic reports and images.
Index Terms: Computers • Intranet • Picture archiving and communication system (PACS) • Radiology reporting systems
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Introduction
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In early 1997, we decided to implement a picture archiving and communication system (PACS) based on personal computers (PCs) and Windows NT (Microsoft, Redmond, Wash) at our private institute. We integrated this system with our radiology information system (RIS). Although the cost-benefit value of PACS is often positive for hospitals (1), where radiologic images need to be archived and distributed, a PACS is more difficult to justify for a private institute, which may not have the same needs. However, cost-benefit considerations for a PACS extend far beyond purely economic issues (2,3).
Although our first, heterogeneous RIS-PACS integration was quite successful, we decided to develop a more homogeneous, high-performance Windows NT–based system. In this article, we provide a description of the system and present the performance of the system.
The integration of PACS and RIS seems to be necessary for realization of an efficient global system (4–10). We believe that recent standard PC-based software and hardware tools now permit such a system to be realized at an affordable price (11–15). Ultimately, such a system will also enable integration of digital medical knowledge and decision aid tools (16–18).
The experience gained during several years of work at our imaging institute allowed us to determine the institute's global needs in managing its data. Not only do radiologists need to view, archive, and retrieve patients' images, they also need to retrieve and recall complex and rare pathologic, anatomic, and radiologic knowledge and compile, retrieve, and consult medical records and reports. Finally, they have to be able to communicate results to referring physicians and colleagues. Classically, radiologists perform these activities using handbooks, papers, film images, luminescent panels, "hard" archives, telephones, mail, and dictating machines. Furthermore, their secretaries have to manage patient data such as demographics, addresses, and billing, as well as scheduling (diary) and report typing. The purpose of a fully integrated RIS-PACS system is to make all such activities less cumbersome, swifter, more user-friendly, and more efficient.
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Description of the System
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Our criteria for selection of hardware and software were a high degree of standardization, interoperability, reliability, and low cost. The system architecture is shown in Figure 1. All of the imaging modalities are connected to the system via DICOM (19). The specific modalities in the environment are shown in Figure 2. All database queries are performed with Microsoft SQL.
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Figure 1. Functional elements of the RIS-PACS system. CAD = computer-assisted diagnosis; CD-ROM = compact disk, read-only memory; DICOM = Digital Imaging and Communications in Medicine; HTML = hypertext markup language; JPEG = Joint Photographic Experts Group; SQL = Structured Query Language; Web = World Wide Web.
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Figure 2. Technical implementation chart for the RIS-PACS system. CT = computed tomography, ISDN = Integrated Services Digital Network, MRI = magnetic resonance (MR) imaging, RAID = redundant array of inexpensive disks, US = ultrasonography.
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Images and reports can be distributed to referring physicians in the form of multimedia HTML and JPEG documents, which can also be used for quick and easy archiving, distribution, and reviewing within our institute. The JPEG compression ratio goes down to 10% of the original file size without a noticeable change in the quality of the image (20–23). In our experience, the limiting factor is not the JPEG images themselves but the poor quality of the low-end public monitors used to view them (24–33). With very high quality gray-scale monitors (eg, SMM monitor [Siemens, Erlangen, Germany] or MedDis monitor [Barco Display Systems, Kortrijk, Belgium]), the quality of JPEG images ranges from satisfactory to good, especially for reviewing purposes (15,21,27,32,33). The main drawback of JPEG images relative to DICOM images is that JPEG images have only an 8-bit (256) gray level depth, whereas DICOM images have a 12-bit (4,096) or greater gray level depth. JPEG images displayed on a high-quality monitor are comparable with images displayed as hard copies (film) (32–36). Once the most appropriate window level and window width for a gray-scale image are selected, the possibility of a 12-bit gray level depth becomes less important. The DICOM viewer software in our system (RxView; WDS Technologies, Geneva, Switzerland) can be adapted to automatically generate HTML-JavaScript code and JPEG images.
The reporting function of the RIS system includes scheduling, demographics, patient information, and billing database components, which consist of a collection of ActiveX modules running within the browser. ActiveX is written in the powerful object-oriented Delphi language (Borland International, Scotts Valley, Calif), and the database is an SQL server (Microsoft).
We selected the Windows NT operating system and network. We added AltaVista (Palo Alto, Calif) indexing and search engines (off-line version) to find lost HTML documents and perform statistical and scientific investigation of our reports. Every day, the AltaVista software automatically indexes the new HTML reports. Our networks are linked to the Internet (Figs 1, 2).
There are three main local client-server networks (Fig 2). (a) The Sienet network (Siemens) is a common network of digital imaging modalities. (b) A fast Ethernet network, called the PACS network, is linked to the DICOM Windows NT server, most of the individual PC stations, the Sienet, and the digitizer station. DICOM messages and files are the main data type flowing through these two networks. (c) A second fast Ethernet network, called the RIS network, is linked to the RIS and mini-PACS Windows NT server and all the individual PC stations. JPEG images, HTML files, and SQL data are the main data types flowing through this network. We physically separated the system into these three parts to avoid conflict between data flow and thus prevent a slowing down of the system. Nevertheless, users at the terminal workstations do not notice the three networks and can use the system transparently. The two Ethernet networks use the transmission control protocol/Internet protocol (TCP/IP) stack and form the intranet of the institute. The main link between these two networks is the PC terminal stations. These stations can retrieve and read DICOM files from the PACS network and can push, retrieve, or read generated HTML and JPEG files from the RIS network. A secondary direct link exists between the two Windows NT servers for automatic patient data coordination.
Four digital imaging units that produce DICOM images are linked to the Sienet: a 1.5-T Magnetom Vision (Siemens) with a Spark 10 computer (Sun Microsystems, Mountain View, Calif); a 0.2-T Magnetom Open (Siemens) with a Spark 2 computer (Sun Microsystems); a Somatom Plus 4 (Siemens); and a Sonoline Elegra Advanced (Siemens). In a few months, a Multix-Universal FD unit (direct digital radiography with a cesium iodide detector and a matrix of 3,000 x 3,000 pixels in 43 x 43 cm) (Siemens) will be installed and linked to the Sienet.
The imaging modalities were interfaced by using RxPACS-Rcv DICOM SCP software (WDS Technologies), which is based on the Merge Technologies (Milwaukee, Wis) DICOM toolkit. There were no major interfacing difficulties.
For digital imaging units that produce non-DICOM images (eg, GCA-7100A gamma camera [Toshiba, Tokyo, Japan] and Siregraph D340–Fluorospot H [Siemens]) and for nondigital imaging units that produce analog film images, a high-quality film digitizer (VXR-12; VIDAR Systems, Herndon, Va) generates digital DICOM files (150–300 dpi, 4,096 gray levels) directly into the PACS network by means of PC-based software (RxView). Because of the very high storage requirements for mammography, this modality has not yet been digitized.
The system has 12 PC terminal workstations (300-MHz Pentium II processor [Intel, Santa Clara, Calif]; 512-kbyte cache; 4-Gbyte hard drive; 128–256-Mbyte random-access memory [RAM]). Eight stations (four radiologists, two secretaries, two technologists) have RxView and are linked to the PACS network. All of the stations are linked to the RIS network. Five stations are linked to the remote extranet server and the Internet via ISDN. The multimedia patient documents (reports and images) in the HTML-JavaScript and JPEG formats can thus be sent to the remote, private, secured extranet server.
The first Windows NT server (450-MHz Pentium II processor [Intel]; 512-kbyte cache; 18-Gbyte hard drive; 512-Mbyte RAM) is dedicated to management and archiving of DICOM images. There are two levels of mass storage media. The first level, for short-term use (~2 weeks), is an 18-Gbyte hard disk. This level allows quick access to recent DICOM files. The second level, for long-term use (several years), consists of write once, read many (WORM) CD-ROM platters, which are managed manually. We do not use expensive CD-ROM jukeboxes for DICOM files because the RIS server allows consultation of all archived (hard disk) images in the JPEG format.
RxView is a multimodality imaging viewer with all the classic functions of such a tool (Fig 3). It is integrated in a succession of DICOM software modules running on PCs in a Windows environment (RxPACS [WDS Technologies]). RxPACS includes other modules, such as an SQL relational database (RxArchive) and hierarchical storage management (HSM). RxArchive allows the manually managed CD-ROMs to be kept in order.
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Figure 3. DICOM viewer (RxView). A main central window displays the images (a). There is also an iconic list of images (b) and the classic functions, tools, and buttons of a PACS viewer (c).
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The second Windows NT server (450-MHz Pentium II processor [Intel]; 512-kbyte cache; 54-Gbyte hard drive; 512-Mbyte RAM) is dedicated to management of the RIS and archiving of patient data (SQL database), reports (HTML), and all images in the JPEG format (mini-PACS). When displayed on a high-quality monitor, the JPEG images are sufficient for image review but perhaps not for diagnosis. Access to these images is rapid and easy because the report and the images are intimately linked (Fig 4). The report is generated by word processing software such as Microsoft Word in the HTML format. The other HTML-JavaScript documents, including the main frame (the home page of the multimedia document) and JPEG images, can be generated by a dedicated software module linked to RxView, from which the radiologist can quickly select images and regions of interest (ROIs). The server uses a redundant array of inexpensive disks (RAID) mirroring system and extensible hard disks (from 54 Gbytes to a higher value) as a mass storage medium (up to 10 years storage) to keep all JPEG images and HTML documents rapidly accessible. Access to HTML and JPEG documents is provided by pointers, which link the patient and report databases to these documents. All valid images are stored in the form of JPEG Web images, exactly as is done with printed images on film (hard copy) daily. All imaging information (report and images) for each patient then becomes quickly available from the hard disk of the RIS network server.
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Figure 4. Web document self-viewer (multimedia). The main (home) page (window) of the document (a) has two frames: The right frame contains the report (b), and the left frame contains the logo of the institute and information about it (c). The "Go to the viewer" button (d) opens a new window (e), which contains the images as well as classic and elementary viewer functions and buttons (f).
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The local RIS-PACS is linked remotely with other workstations and servers via ISDN. From their PC stations, physicians can consult remote biomedical databases and Web documents (bookless radiology). Multimedia patient reports and images can be sent to a private remote extranet server or directly via e-mail (postless radiology) after encoding of the documents for confidentiality. Referring physicians and general practitioners linked to this remote server can therefore download and consult the documents on their patients. The PCs of one or more radiologists at our institute may have access to the RIS and PACS servers directly via ISDN or can be linked to the remote extranet server.
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Performance of the System
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A lossy JPEG compression ratio of 1:10—a little more (1:12) for CT, US, and MR images and a little less (1:8) for conventional x-ray images—is commonly used for the RIS network (Web documents). The size of each Web document (JPEG images and report) varies from 0.5 Mbytes (one x-ray image or echogram) to 8 Mbytes (200 CT or MR images). We therefore produce 150 Mbytes of documents (not including mammograms) per day (~35 Gbytes per year), which seems reasonable given the present, and particularly the future, size and cost of a hard disk.
A lossless compression ratio of about 1:2 is commonly used for the PACS network (DICOM images). The size of each DICOM image study per patient varies from 2.5 to 50 Mbytes. We therefore produce 600–800 Mbytes of DICOM data per day (~160 Gbytes per year, ie, ~170 CD-ROMs per year). Given the present cost of CD-ROMs, this archive is very inexpensive.
The two fast Ethernet networks (100 Mbit/sec) allow high downloading performance: a few seconds for Web documents (RIS) and a few seconds to 30 seconds for DICOM data (PACS). It takes 1–8 minutes to send Web documents via e-mail with ISDN (128 kbit/sec or 16 kbyte/sec), which also seems reasonable. Because radiologists consult old documents (images and reports) for review and comparison with new documents, they prefer to use the Web documents to perform such tasks. Only rarely (maybe less than 2% of the time) do they need to physically retrieve a DICOM CD-ROM and manually put it inside its drive to review old original DICOM images. Over the medium term, we hope to communicate results in the form of Web documents only via e-mail or mass storage media and to reduce production of film images.
Until a few months ago, it was difficult to persuade our referring colleagues to accept Web documents, despite their advantages, in place of images on film and reports on paper. As more and more physicians are professionally connected to the Internet, this situation is hopefully changing rapidly.
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Conclusions
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The system described herein or a similar one may form the short-term future radiologist's office. Cost-benefit considerations are taken into account when evaluating such an electronic office system, as well as the fact that a RIS-PACS system allows less cumbersome, swifter, more user-friendly, and more efficient activity for radiologists. In turn, this fact means that throughput of image review by radiologists increases because image access is quicker and easier. These new characteristics provide "added value" and higher performance for patient care. Even though a complete evaluation has yet to be performed, it would appear that the manner in which radiologists work is changing and that their activity is progressively becoming more efficient and swifter at our institute.
We have not met any serious technical difficulty in implementing the RIS-PACS system and have experienced no significant problem with DICOM images generated by the imaging units. The current hardware and software performance of the PC environment seems to be well-adapted, and their affordability makes development of this system possible. Furthermore, we have not encountered the typical problems experienced by hospitals in adapting and linking the existing hospital information systems (HISs) to the new RIS-PACS.
One of the advantages of multimedia HTML-JPEG documents on patients is that referring physicians are able to read them with standard Web browsers and without investing in expensive hardware or software. Despite this overwhelming advantage, we still have difficulty convincing referring colleagues to use this new means of communication. The main reason given is the fear of not being able to overcome supposed complex technical problems.
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Footnotes
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Abbreviations: CD-ROM = compact disk
read-only memory; DICOM = Digital Imaging and Communications in Medicine; HTML = hypertext markup language; ISDN = Integrated Services Digital Network; JPEG = Joint Photographic Experts Group; PACS = picture archiving and communication system; PC = personal computer; RIS = radiology information system; SQL = Structured Query Language
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Abstract
Introduction
