A fail safe Computed Radiography PACS segment at Conquest Hospital
David Baker, Keith Foord and Nigel Tomlinson*
Department of Radiology, Conquest Hospital, The Ridge, St Leonards on Sea, East Sussex, UK and * Capitec Scientific Services, NHS Estates, Department of Health, Frant House, Coach and Horses Passage, Tunbridge Wells, Kent, UK
Abstract
The Conquest group described practical issues and difficulties with a single Fuji AC2 based (Philips ACe) computed radiography (CR) unit at EuroPACS ‘94 in Geneva . With increasing reliance on CR for plain image work the issues of a critical single point of failure and of plate processing capacity became more important. In 1996 it was decided to completely replace the old facility with a triplicated CR segment with high intrinsic single point of failure protection.
At replacement in December 1997 following a competitive tender, the ergonomic issues of manual data input, image optimisation, rotation, annotation, cropping etc. were addressed. The opportunity was also available to take advantage of hospital re-networking to migrate from the dedicated radiology departmental bi-directional triangular 100 Mbits/s FDDI network with Cabletron hubs to the use of a new 2 x 100 Mbits/s FDDI hospital wide network with Anite switched hubs under VLAN control to enable fast switching and optimised routing.
With the old CR network there was manual input of patient demographics and examination detail at ID stations. Within the Philips ACe plate reader and its associated PC computer the Fuji/Philips firmware manipulated images. Data export to the image preview and routing station was in SPI (ACR-NEMA 2 ) format. No manipulation of images was possible on the preview station. Data was then exported to PACS and archived on RAID immediately. The maximum rate of CR plate throughput rarely exceeded 25 plates per hour in clinical practice although the unit was theoretically rated at 40 plates per hour.
Now three ID stations (USITs) are networked to allow input of ASCII patient and examination data from the radiology information system to allow radiographers to select studies without the need for any manual input. Plans exist to migrate to bi-directional HL7 or DICOM RIS -PACS data exchange. Once the study is selected the CR plate is read by the associated Philips AC3 plate reader and the image data transferred to Philips Easyvision workstations. These are themselves networked to allow images to be transferred between them. (Figure). Plate cycle times through each AC3 is 20 seconds for 18 x 24 cm plates, 40 seconds per 24 x 30 cm plate and 50 seconds per 35 x 43 cm plate. Even with the largest plate size total throughput per unit is over 60 plates per hour and if all three are available a total throughput of circa 200 plates per hour is possible, easily coping with maximum demand.
All the ergonomic and image manipulation issues previously described are met by these stations. The Easyvisons are DICOM Patient Study and Image IO conformant and the segment is prepared for full PACS integration. There is local medium term disk buffering shared between the units allowing for approximately 10 days CR work , which means that CR work can continue during PACS downtime. As a bonus the Philips DSI and V3000 rooms are also linked through the Easyvisions. Using this configuration a guarantee of 100% availability of at least one CR/Easyvision combination has been contracted with the CR suppliers. As an interim two of Easyvisions are networked via a separate closed Imation network to an Imation 8800 image server and thence to 8500 and 9700 dry laser imagers. The third Easyvision can print via either of the others. After full PACS re-introduction printing will be via print servers, but the closed laser imager network will be retained for back up.
Conclusion
Within a full PACS 100% availability of plain image acquisition devices must be assured. A triplicated CR PACS segment has been designed and installed which meets these requirements.
Oral presentation at EuroPACS'98, Barcelona, Spain