58
European Journal of Radiologv, 16 (1992) 58-61 0 1992 Elsevier Scientific Publishers Ireland Ltd. All rights reserved. 0720-048X/92/$05.00
EURRAD 00379
Modular implementation of PACS: preliminary results of the RiksPACS project. Design considerations Arve Kaarensen Center of Medical Infomatics, Rikshospitalet.Universityof Oslo, Norway
Key words: Radiology and radiologist, design of radiological facilities; PACS
Introduction Picture Archiving and Communications Systems (PACS) are beginning to play a greater role in radiology departments. In this report we describe the RiksPACS-project and the resulting PACS-system that has been developed at Rikshospitalet, University of Oslo, Norway. The background of the project is the increasing need of effective image management systems. Furthermore, radiologic imaging equipment is becoming increasingly digital. The increased dynamic range of the digital imaging systems and the number of images per study require the use of digital viewing stations that permit interactive contrast manipulation and rapid image presentation. The current film-based system limits the potential effectiveness of the digital image technology. As we searched the market for PACS systems during the late 8Os, we found that the market was dominated by large, proprietary systems intended for fully digitalized radiology departments. The initial cost of implementing such systems was far too high. Some hospitals had tried (e.g. St. Mary’s hospital in London), and experienced great difhculties in implementing this ‘total approach’ to PACS. We therefore decided to base our approach on the concept of modular, distributed systems based on open technology. It was our belief, and still is, that this concept is the only possible approach to a successful implementation of PACS. Modular systems make it posCorrespondence to: Arve Kaarensen, Center of Medical Infoxmatics, Rikshospitalet, University of Oslo, Pilestredet 32, 0027 Oslo 1 Norway.
sible to implement PACS in a step-wise manner, beginning with a minimum configuration of one combined server/viewing station acquiring images from one imaging modality, and adding new modules as the needs grow. The market, however, was not ready for this philosophy. In 1989 we therefore decided to join a project aiming at developing a system based on the above concept. History of the RiksPACS project The RiksPACS-project was initiated January 1989 as a cooperation between Rikshospitalet, the University Center of Information Technology and Maptech A/S. Our industry partner, Maptech A/S, had experience in developing systems for digital maps. We found that their prototyping tools could easily be applied to developing a system for presentation of radiologic images. The tools were based on standard UNIX workstations with the X11 windowing system, and could generate applications with built-in interfaces to the Oracle database management system. Thus, they fully matched our concept of open technology as a platform for development of PACS. The section of neuroradiology was chosen to be the user environment of the project. The reason of this choice was that this section is heavily dependent on digital imaging equipment (MRT, CT, DSA). Furthermore, this section has a substantial communication need with the section of pediatric radiology, which is situated in another building some 200 m from the main radiology building. Thus, this environment seemed very well fit to study all aspects of a PACS (acquisition from different modalities, archiving of large amounts of im-
59
ages, communication, viewing of images both at local and remote stations). The project had a budget of 5.2 million NOK over a time period of 18 months. The time schedule was very tight, with 3 milestones: 1. July 1st 1989: A pilot system consisting of one combined server/workstation presenting images from MR. 2. February 1st 1990: A test version consisting of an archive server and 2 workstations presenting images from MR and CT. 3. July 1st 1990: A final version to be ready for clinical use. The first milestone was reached as scheduled. During the work towards the second milestone, however, the project ran into several problems. The main problem was the difficulty of interfacing the CT. This reveals what must be stated as the main problem regarding PACS: Image acquisition. We will discuss this problem in part 2 of this report. The acquisition problem not only delayed the project by 3 months. It also led to some financial problems, which in turn led to further delay of the project. The problems did not become less when our industry partner went bankrupt, and was purchased by a competing company, SysScan Technology A/S. The new owner was still interested in the project, but with more restrictive investment policy. Despite these problems the development continued, mainly because of the hospital staff and their belief in the system that began to take form of a product. Currently, an agreement exists between IBM, Cap Gemini and Medinnova, Rikshospitalet. This agreement states that IBM is responsible for marketing of RiksPACS and Cap Gemini is responsible of support and development of the product. Medinnova is a government owned company constituting the link between the researchers at Rikshospitalet and the industry. Medinnova is the copyrights owner of RiksPACS. What is PACS
PACS includes: Picture Archiving Communication Systems
viewing at diagnostic, consultation and remote workstations. on magnetic or optical media using short-or long-term storage devices. using local or wide area networks. that include modality interfaces, Information Management Systems and interfaces to Hospital Information
System (HIS) and Radiology Information Systems (RIS). Main requirements
The rapid development in information technology calls for PAC-systems with abilities to incorporate new technology as it develops. At the same time the organizational environment is a subject to dynamic changes. These facts impose some important conceptual requirements to the design of PACS. In short, the requirements could be listed as: l modularity l flexibility l scalability 0 ease of use l vendor independency Modularity means that the system should be broken into logically independent modules enabling freedom of choice regarding each submodule (e.g. database technology, compression methods, aquisition methods, communication protocols, tile formats etc.) Flexibility means that the system ensures adaptability to new requirements, both technical and organizational. Scalability means that the system should be costeffective for small environments as well as huge, fully digitalized radiology departments. Ease of use because PACS is a tool in diagnostic work and not a goal in itself. Vendor independency means that the system should be able to run on different hardware platforms, both to ensure a certain level of competition between vendors had to be able utilize the optimal hardware at any time. The main requirements listed above call for an important principle regarding design: standardization. Standardization should be implemented at every possible level, i.e. standardization of: l workstation operating systems (UNIX) l Data Base Management Systems (SQL-based Relational DBMS) l communication protocols (TCP/IP, OSI, ACRNEMA v.3.0) l image storage formats (ACR-NEMA, PAPYRUS) l compression methods (JPEG, MPEG, CCITT, ACR-NEMA) 0 user interface tools (X 11) l progr amming languages (ANSI C) The RiksPACS design
RiksPACS is an example of a system designed according to the requirements and principles mentioned
60
above. The system is based on an open architecture and can be executed on various workstation and server platforms. The system is currently implemented on all of the major workstation vendors (IBM, HP, SUN, DEC). The program code is written in the C-language, and is based on industrial standards like UNIX operating system, TCP/IP communication protocols, NFS tile system, SQL-based RDBMS (ORACLE), and X11 window system. Figure 1 describes a logical draft of the system. Refering to the draft the system is partitioned into 6 modules: Acquisition module Compression/decompression module Archiving module Database module Display module Operator module This modular construction ensure a great extent of flexibility regarding the physical implementation of the system. Acquisition module The acquisition module constitutes the interface to-
ward the imaging modalities. As shown in Fig. 2 the module consists of different submodules, import procedures, each of which is specific to the imaging modality in question. The import procedures take care of the physical transfer of pictures from the imaging modality to RiksPACS. The pictures are then converted to a common format and transferred to the archiving module for storage. Compression/decompression module
By separating the compression/decompression function into its own module, RiksPACS makes it possible
0 P
m
I
Acquisition
I
Compression
1
Archive
module
module
module
I I (
Fig. 1. RiksPACS logical design.
to implement different methods of compression. To date RiksPACS is based on the standard Lempel Ziv Welch lossless compression. This gives a compression factor of 1.5-2. We are currently experimenting with different kinds of lossy methods with compression factors of 2-20. The results of these experiments will decide whether the quality of the reconstructed picture is acceptable from a diagnostic viewpoint or not. Archiving module
The archiving module is administering the physical location of the picture on long- and short-term storage. All changes in storage structure is handled by this module. New examinations coming from the acquisition module are stored both on long-term (optical) storage and short-term (magnetic) storage. The short-term storage is organized by the FIFO-principle (First In First Out). This means that the new examinations are immediately accessible on the workstations, while the old examinations must be ordered by the operator module before they can be displayed on screen. The long-term storage is based on optical WORMdisks (Write Once Read Many) which guarantee a storage time of 30 years. The write once principle ensures that pictures stored in long-term storage cannot be erased. Database module
The database module constitutes the link between the different RiksPACS modules. All necessary information on patients, examinations, pictures and storage locations is stored in a relational database. By using a SQL-based database management system RiksPACS can easily be integrated with HIS/RIS systems, Display module The display module handles the interrelation with
the user. It consists of a base system, programmed in C, running on UNIX workstations with the Xl 1 window system. This base system contains an interpreter that makes it possible to tailor the user interface by means of a high level procedure oriented command language. This makes RiksPACS very flexible concerning adjustments to user requirements. The user interface is highly mouse-oriented. All functions are triggered by menu choices. Operator module
l-&ggk--~ Fig. 2. Acquisition module logical design.
The operator module consists of a number of routines to administrate the RiksPACS system. Routines that is included are:
61
Conducting the acquisition procedures Fetching of pictures from long-term storage Removing of pictures from short-term storage Mounting/dismounting of optical disks Backup Configuring of the system Network administration User administration
Current configuration of RiksPACS
Figure 3 describes the current configuration of RiksPACS at department of radiology, Rikshospitalet. The system consists of: a combined acquisition/archiving server situated in the MR computer room. The server is a IBM RS6000 mod. 520 with 32 Mb RAM and 4.2 GB magnetic disk. Connected to the server is a LF 4500 Rapid Changer (Laser Magnetic Storage) with a capacity of 28 GB online WORM optical storage. A diagnostic viewstation situated in the demonstration room, section of neuroradiology. It is a IBM RS6000 mod. 320 with 32 MB RAM, 330 MB magnetic disk and two 1K x 1K 256color displays. A diagnostic viewstation situated in the demonstration room, section of pediatric radiology. A Siemens Hardware Gateway Module Constituting the link between the archive server and the Siemens CT. An ethernet LAN between the network nodes.
m
Working Station
Fig. 3. RiksPACS
7I
configuration at Rikshospitalet.
Future plans: Connecting the network to a hospital wide network that is planned implemented this year (Possible FDDI backbone with ethernet segments in each department) Enhancing the aquisition module to interface the GE DSA. Connecting the system to a laser film printer for hardcopies. Placing remote viewing stations in department of neurosurgery. Integrating RiksPACS with RIS/HIS
European Journal of Radiologv, 16 (1992) 58-61 0 1992 Elsevier Scientific Publishers Ireland Ltd. All rights reserved. 0720-048X/92/$05.00
EURRAD 00379
Modular implementation of PACS: preliminary results of the RiksPACS project. Design considerations Arve Kaarensen Center of Medical Infomatics, Rikshospitalet.Universityof Oslo, Norway
Key words: Radiology and radiologist, design of radiological facilities; PACS
Introduction Picture Archiving and Communications Systems (PACS) are beginning to play a greater role in radiology departments. In this report we describe the RiksPACS-project and the resulting PACS-system that has been developed at Rikshospitalet, University of Oslo, Norway. The background of the project is the increasing need of effective image management systems. Furthermore, radiologic imaging equipment is becoming increasingly digital. The increased dynamic range of the digital imaging systems and the number of images per study require the use of digital viewing stations that permit interactive contrast manipulation and rapid image presentation. The current film-based system limits the potential effectiveness of the digital image technology. As we searched the market for PACS systems during the late 8Os, we found that the market was dominated by large, proprietary systems intended for fully digitalized radiology departments. The initial cost of implementing such systems was far too high. Some hospitals had tried (e.g. St. Mary’s hospital in London), and experienced great difhculties in implementing this ‘total approach’ to PACS. We therefore decided to base our approach on the concept of modular, distributed systems based on open technology. It was our belief, and still is, that this concept is the only possible approach to a successful implementation of PACS. Modular systems make it posCorrespondence to: Arve Kaarensen, Center of Medical Infoxmatics, Rikshospitalet, University of Oslo, Pilestredet 32, 0027 Oslo 1 Norway.
sible to implement PACS in a step-wise manner, beginning with a minimum configuration of one combined server/viewing station acquiring images from one imaging modality, and adding new modules as the needs grow. The market, however, was not ready for this philosophy. In 1989 we therefore decided to join a project aiming at developing a system based on the above concept. History of the RiksPACS project The RiksPACS-project was initiated January 1989 as a cooperation between Rikshospitalet, the University Center of Information Technology and Maptech A/S. Our industry partner, Maptech A/S, had experience in developing systems for digital maps. We found that their prototyping tools could easily be applied to developing a system for presentation of radiologic images. The tools were based on standard UNIX workstations with the X11 windowing system, and could generate applications with built-in interfaces to the Oracle database management system. Thus, they fully matched our concept of open technology as a platform for development of PACS. The section of neuroradiology was chosen to be the user environment of the project. The reason of this choice was that this section is heavily dependent on digital imaging equipment (MRT, CT, DSA). Furthermore, this section has a substantial communication need with the section of pediatric radiology, which is situated in another building some 200 m from the main radiology building. Thus, this environment seemed very well fit to study all aspects of a PACS (acquisition from different modalities, archiving of large amounts of im-
59
ages, communication, viewing of images both at local and remote stations). The project had a budget of 5.2 million NOK over a time period of 18 months. The time schedule was very tight, with 3 milestones: 1. July 1st 1989: A pilot system consisting of one combined server/workstation presenting images from MR. 2. February 1st 1990: A test version consisting of an archive server and 2 workstations presenting images from MR and CT. 3. July 1st 1990: A final version to be ready for clinical use. The first milestone was reached as scheduled. During the work towards the second milestone, however, the project ran into several problems. The main problem was the difficulty of interfacing the CT. This reveals what must be stated as the main problem regarding PACS: Image acquisition. We will discuss this problem in part 2 of this report. The acquisition problem not only delayed the project by 3 months. It also led to some financial problems, which in turn led to further delay of the project. The problems did not become less when our industry partner went bankrupt, and was purchased by a competing company, SysScan Technology A/S. The new owner was still interested in the project, but with more restrictive investment policy. Despite these problems the development continued, mainly because of the hospital staff and their belief in the system that began to take form of a product. Currently, an agreement exists between IBM, Cap Gemini and Medinnova, Rikshospitalet. This agreement states that IBM is responsible for marketing of RiksPACS and Cap Gemini is responsible of support and development of the product. Medinnova is a government owned company constituting the link between the researchers at Rikshospitalet and the industry. Medinnova is the copyrights owner of RiksPACS. What is PACS
PACS includes: Picture Archiving Communication Systems
viewing at diagnostic, consultation and remote workstations. on magnetic or optical media using short-or long-term storage devices. using local or wide area networks. that include modality interfaces, Information Management Systems and interfaces to Hospital Information
System (HIS) and Radiology Information Systems (RIS). Main requirements
The rapid development in information technology calls for PAC-systems with abilities to incorporate new technology as it develops. At the same time the organizational environment is a subject to dynamic changes. These facts impose some important conceptual requirements to the design of PACS. In short, the requirements could be listed as: l modularity l flexibility l scalability 0 ease of use l vendor independency Modularity means that the system should be broken into logically independent modules enabling freedom of choice regarding each submodule (e.g. database technology, compression methods, aquisition methods, communication protocols, tile formats etc.) Flexibility means that the system ensures adaptability to new requirements, both technical and organizational. Scalability means that the system should be costeffective for small environments as well as huge, fully digitalized radiology departments. Ease of use because PACS is a tool in diagnostic work and not a goal in itself. Vendor independency means that the system should be able to run on different hardware platforms, both to ensure a certain level of competition between vendors had to be able utilize the optimal hardware at any time. The main requirements listed above call for an important principle regarding design: standardization. Standardization should be implemented at every possible level, i.e. standardization of: l workstation operating systems (UNIX) l Data Base Management Systems (SQL-based Relational DBMS) l communication protocols (TCP/IP, OSI, ACRNEMA v.3.0) l image storage formats (ACR-NEMA, PAPYRUS) l compression methods (JPEG, MPEG, CCITT, ACR-NEMA) 0 user interface tools (X 11) l progr amming languages (ANSI C) The RiksPACS design
RiksPACS is an example of a system designed according to the requirements and principles mentioned
60
above. The system is based on an open architecture and can be executed on various workstation and server platforms. The system is currently implemented on all of the major workstation vendors (IBM, HP, SUN, DEC). The program code is written in the C-language, and is based on industrial standards like UNIX operating system, TCP/IP communication protocols, NFS tile system, SQL-based RDBMS (ORACLE), and X11 window system. Figure 1 describes a logical draft of the system. Refering to the draft the system is partitioned into 6 modules: Acquisition module Compression/decompression module Archiving module Database module Display module Operator module This modular construction ensure a great extent of flexibility regarding the physical implementation of the system. Acquisition module The acquisition module constitutes the interface to-
ward the imaging modalities. As shown in Fig. 2 the module consists of different submodules, import procedures, each of which is specific to the imaging modality in question. The import procedures take care of the physical transfer of pictures from the imaging modality to RiksPACS. The pictures are then converted to a common format and transferred to the archiving module for storage. Compression/decompression module
By separating the compression/decompression function into its own module, RiksPACS makes it possible
0 P
m
I
Acquisition
I
Compression
1
Archive
module
module
module
I I (
Fig. 1. RiksPACS logical design.
to implement different methods of compression. To date RiksPACS is based on the standard Lempel Ziv Welch lossless compression. This gives a compression factor of 1.5-2. We are currently experimenting with different kinds of lossy methods with compression factors of 2-20. The results of these experiments will decide whether the quality of the reconstructed picture is acceptable from a diagnostic viewpoint or not. Archiving module
The archiving module is administering the physical location of the picture on long- and short-term storage. All changes in storage structure is handled by this module. New examinations coming from the acquisition module are stored both on long-term (optical) storage and short-term (magnetic) storage. The short-term storage is organized by the FIFO-principle (First In First Out). This means that the new examinations are immediately accessible on the workstations, while the old examinations must be ordered by the operator module before they can be displayed on screen. The long-term storage is based on optical WORMdisks (Write Once Read Many) which guarantee a storage time of 30 years. The write once principle ensures that pictures stored in long-term storage cannot be erased. Database module
The database module constitutes the link between the different RiksPACS modules. All necessary information on patients, examinations, pictures and storage locations is stored in a relational database. By using a SQL-based database management system RiksPACS can easily be integrated with HIS/RIS systems, Display module The display module handles the interrelation with
the user. It consists of a base system, programmed in C, running on UNIX workstations with the Xl 1 window system. This base system contains an interpreter that makes it possible to tailor the user interface by means of a high level procedure oriented command language. This makes RiksPACS very flexible concerning adjustments to user requirements. The user interface is highly mouse-oriented. All functions are triggered by menu choices. Operator module
l-&ggk--~ Fig. 2. Acquisition module logical design.
The operator module consists of a number of routines to administrate the RiksPACS system. Routines that is included are:
61
Conducting the acquisition procedures Fetching of pictures from long-term storage Removing of pictures from short-term storage Mounting/dismounting of optical disks Backup Configuring of the system Network administration User administration
Current configuration of RiksPACS
Figure 3 describes the current configuration of RiksPACS at department of radiology, Rikshospitalet. The system consists of: a combined acquisition/archiving server situated in the MR computer room. The server is a IBM RS6000 mod. 520 with 32 Mb RAM and 4.2 GB magnetic disk. Connected to the server is a LF 4500 Rapid Changer (Laser Magnetic Storage) with a capacity of 28 GB online WORM optical storage. A diagnostic viewstation situated in the demonstration room, section of neuroradiology. It is a IBM RS6000 mod. 320 with 32 MB RAM, 330 MB magnetic disk and two 1K x 1K 256color displays. A diagnostic viewstation situated in the demonstration room, section of pediatric radiology. A Siemens Hardware Gateway Module Constituting the link between the archive server and the Siemens CT. An ethernet LAN between the network nodes.
m
Working Station
Fig. 3. RiksPACS
7I
configuration at Rikshospitalet.
Future plans: Connecting the network to a hospital wide network that is planned implemented this year (Possible FDDI backbone with ethernet segments in each department) Enhancing the aquisition module to interface the GE DSA. Connecting the system to a laser film printer for hardcopies. Placing remote viewing stations in department of neurosurgery. Integrating RiksPACS with RIS/HIS
