Displaying dynamic medical images "on the fly" with the MBASE "Video PACS" solution

Lyon 02 October 2000Within the Transfer Technology Nodes (TTN) support network for High Performance Computing and Networking (HPCN), six French partners have worked together to build and validate a Medical Image Server based on a parallel computer architecture. The idea for this best practice activity was to generate a service which smoothly can deal with dynamic medical images in and outside the hospital environment. The new "Video PACS" solution developed by the MBASE project team, provides on-demand instant access to animated images without the need for huge storage and processing capabilities on the client side. The system has extensively been tested at the pilot site of the Louis Pradel Hospital in Lyon.

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Medical images associated with patient records should be readily available throughout the hospital site for communication and management. The existing Picture Archiving and Communications Systems (PACS) however are only able to transmit still images and video film from the source modality to a dedicated consultation workstation in time-devouring push mode. On-demand access to visual patient material is restricted to the radiologist who is responsible for a specific modality such as angiography or sonography. If the patient studies are not saved on S-VHS tapes or CD-ROM, the results of the examination soon will be lost due to the limited internal disk space of the radiology information systems.

In addition, the conventional archiving methods give rise to quality reduction and data loss. To solve these issues, the MBASE team decided to use parallel database and storage technology next to high speed client/server networking which has to guarantee an improved batch and on-line handling of the image data and an on-demand delivery of patient video results for daily clinical use across the entire hospital. The database management specialists at the LIP Laboratory from the Ecole Normale Supérieure de Lyon and at Ardent Software worked in close collaboration with MATRA Systèmes & Information, the HPCN expert, to design the system. In addition, there were three medical end-users to evaluate MBASE at the Hospital Pradel, including the Association of French Radiologists (SFR), and CREATIS and INSERM, two medical research laboratories.

The MBASE team aimed at creating a computer-assisted diagnosis-oriented imaging environment. The MBASE server storage and the parallel database engine were built to overcome potential performance bottleneck problems in traditional DICOM protocol-based solutions. These two demonstrators allow to treat complex, simultaneous queries in a multi-user client/server setting. On the one hand, radiological diagnostic clients are connected to the storage offering exclusive write access via the low-cost non-switched Fibre Channel Storage Area Network (SAN) technology. On the other hand, a switched fast Ethernet provides easy access to the clustered image server from anywhere in the hospital. As such, a parallel gateway system is established with the hospital LAN, providing three times the bandwidth of a high-end Symmetric Multi-Processor (SMP) machine at an equal cost.

The MBASE server radiological gateway is fully compatible with the current DICOM PACS standard but integrates a faster alternative with "Video PACS", based on the JPEG format for static images and on lossy image compression with MPEG-1 and MPEG-2 for dynamic images. Two scenarios, on the workflow and on-demand image access, were selected by the team to compare DICOM PACS to "Video PACS" performance rates. In the workflow setting, image-handling immediately follows a patient examination. The system moves the visual data to the server or a doctor's workstation with a delay referred to as transfer time. In the on-demand scenario, there is no anticipation to a previous exam. The physician only requests to consult a set of patient data and the delay needed to deliver the images is the access time.

During the evaluation tests at the Hospital Pradel, measurements have been carried out for the two types of delay. Whereas in DICOM the file first has to be completely stored on the client side before it is accessible, in the MBASE "Video PACS" solution, the server is streaming the data, allowing the doctor to already display the patient file while it is still being transmitted over the network. Whether on-demand or on the workflow access to images is required, it makes absolutely no difference anymore to the MBASE server. Simultaneous multi-user access to the system is provided with less than 30 seconds latency instead of a few minutes with the DICOM protocol, while on-demand access to animated images is improved from an average of nineteen minutes to merely two seconds. These results will stimulate hospital staff to make more frequent use of PACS applications.

At the Hospital Pradel, the MBASE system was tested for cardiology but this solution can also be applied to other medical specialities such as obstetrics. The team equally demonstrated that a very fast access to the DICOM format file can be established by connecting the existing DICOM workstations to the high performance Fibre Channel Storage Area Network of the MBASE server. More details on the MBASE system can be obtained from the project contact person Pierre Croisille. The brochure "Image Processing and Parallel Computing in Medical Applications" also comprises a description of MBASE, next to a host of other TTN medical parallel computing projects, which were carried out under the Esprit programme, funded by the European Union. This publication can be ordered on-line at the all-in price of DM 45,- at AT&M Technologie und Marketing GmbH.


Leslie Versweyveld

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