review article picture archiving and communication system - rbrs

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non- or pre-DICOM communication standards between their modalities and workstations with a special gateway to the outside DICOM world (5). PACS-RIS-HIS integration A fundamental tenet of current PACS implementations is that images should not be available without information. Therefore, each PACS has a mechanism for linking the pertinent patient information (e.g. demographics, clinical history, allergies) with the image. Each image data set must be “labelled” or identified with a specific patient and linked to a patient folder or some other useful construct within PACS. Therefore, there are two components to a PACS archive. One component is the database that maintains patient metadata information and the other component is the file server that actually stores the image data sets (37). Current PACS with secure Internet or Intranet web techniques, enables rapid and simultaneous access to images in different physical locations. With prompt interpretation and voice recognition technology, reports should be available rapidly and may automatically be associated and delivered with the images (36). However, such successful PACS implementation requires RIS and HIS integration. Many institutions already have a HIS or RIS in place in addition to the PACS information system. Ideally, these systems should be integrated for image management. The most important roles of HIS related to PACS are to provide a “clean” master patient index that identifies every patient uniquely on a one-toone basis, as well as to provide admission, transfer, and discharge information. The RIS provides notification of events – particularly the scheduling of an imaging procedure, with relevant clinical information. The RIS provides unique identification of the imaging procedures requested and performed, allowing PACS to handle and archive them unambiguously, and to associate a diagnostic report with each study (36). Problems may occur even with highly integrated PACS-RIS-HIS. One of the most bothersome is that the PACS database, even with the best pre-fetching, usually is unaware of prior studies existing only on film. In addition, the present RIS database usually does not dis- PICTURE ARCHIVING AND COMMUNICATION SYSTEM — DE BACKER et al. 239 tinguish between studies on film and those archived digitally, without film (36). For most cross-sectional examinations, such as CT and MRI, the technologist manually enters patient demographic information into the acquisition device. The study and associated information are then “pushed” into PACS via a gateway (preferable using the DICOM standard). PACS then needs to handle or deal with both the image data set and associated information. If a HIS/RIS/PACS communication link is in place, then PACS attempts to match the incoming study with what exists on its database. If a discrepancy occurs, PACS may reject the study (i.e., not allow into the system), place it on the special list (e.g., “unspecified folder”, “exceptions list”, or “penalty box”), or create a new patient folder (i.e., new study) with the erroneous data. This scenario is not uncommon because dual entry of patient information is fraught with problems, including a substantial potential for misspelling and other alphanumeric data errors (e.g., transpositions). Another problem that is not specific to digital image storage but in a full PACS environment occurs when a patient has been assigned a new patient identification number in the HIS or RIS on a repeat visit to the hospital. This results in previous images not being found in the PACS archive. In both situations operator intervention is required to rectify the situation. An operator must then have access to a PACS workstation to identify the problem and accomplish a solution “after the fact” (5, 38). PACS should be considered part of the hospital infrastructure with distribution of radiological images throughout the hospital. Through an appropriate HIS/RIS/PACS interface, the current location of a patient in the hospital is made known to PACS to enable the correct distribution of images to the clinics and wards. In the future, viewing of radiological images should become an integrated part of the HIS. Both to assure data security of the PACS archive and to provide fast access to the users, image distribution throughout the hospital should be accomplished by using one or more separate image servers (5). PACS workflow Early PACS installations focused on just providing the most basic PACS functions, image retrieval and viewing. Workstations were rather clumsy and tended to reflect a lack of experience and understanding of radiologists’ work habits. Continuous technological improvement and better understanding of workflow within PACS resulted in a broader level of acceptance by radiologists. Workstation design and system architecture have improved as many institutions and manufacturers actively involved radiologists in the design process, resulting in the development of user-friendly workstations that are more suitable for the radiologists’ task. The smooth flow of images to the location at which they are needed, at the time they are needed, and displayed in the preferred manner as required by the radiologist to achieve both with efficiency and high diagnostic accuracy, requires management of the studies. This study management, often referred to as folder management, provides PACS with intelligent functionality for image acquisition, routing, storage, presentation, and retrieval functions (36,39). For example, when a patient is scheduled for a given type of procedure, the workflow manager will know where the images are likely to be viewed, what prior studies are relevant and prefetch these studies from the longterm archive and then to the workstation before the arrival of the images from the current study. Reports from prior procedures will be available at the workstation. When the study is completed the images are automatically sent to PACS and routed to the appropriate workstation. When the new study is called up for review, images appear in the correct sequence and at the appropriate window width and level. Prior images are available immediately for display. To ensure an ergonomic interface, an operating system based on the windows metaphor may be used for the viewing station. Image preprocessing with its potential to improve visualization of certain radiographic findings may often be very time-consuming with current workstations and, therefore, is rarely used in clinical routine. However, many preprocessing tasks could be automated by appropriate software. Automatic arrangement of images in pre-set orders and managed by a rule-based system may be provided. In soft-copy viewing of radiological images, it is often desirable to block out white, unexposed image areas.
240 JBR–BTR, 2004, 87 (5) Current workstations may provide dark shutters to manually exclude peripheral white image areas from being displayed. With appropriate segmentation software, this task may be automated. Automatic optimisation of window settings, image enlargement (zoom) and translation (pan) are other examples. In addition to conventional viewing of CT and MRI examinations, the DVS may provide the possibility to scan through virtual stacks of images (stack or cine-mode) or may allow stepping parallelly through two or more stacks of images (actual and previous examination, examination without and with contrast medium, different MR sequences) resulting in faster interpretation and reporting time. Finally, some calibrated quantification functions are needed: spatial measurements (length, surface, volume) and density measurements (in Hounsfield units for CT). For the acceptance of PACS by non-radiologists, the RVS should be very simple to use in order to avoid extensive user training. The RVS should be able to present the radiological image together with the radiological report because of the nondiagnostic quality of the graphic hardware. Image manipulation function may be limited to image rotation and centre-window adjustment; the images should be presented in a way that demonstrates the radiological findings. Specialized RVS may integrate programs for planning of surgical interventions such as the measurements of the dimensions of a total hip prosthesis. Conclusion Information technology has become a vital component of all health care enterprises and large hospital networks provide the basis of hospital-wide information. The technologic imperative that has been the driving force advancing radiology over the past 20 years has produced new approaches to the acquisition of medical images and placed radiology at the leading edge of the computer-technology era of modern medicine. Ever-increasing computer performance in combination with the advent of the communication standard DICOM makes PACS a reality with numerous small and middle-scale installations, but also with several truly filmless hospitals in operation all over the world (3). PACS is responsible for solving the problem of acquiring, transmitting, and displaying radiological images. Integration of PACS with the HIS and RIS facilitates more informed and presumably more accurate interpretations (40). References 1. Hynes D.M., Stevenson G., Nahmias C.: Towards filmless and distance radiology. Lancet, 1997, 350: 657-60. 2. Langlois S.L., Vytialingam R.C., Aziz N.A.: A time-motion study of digital radiography at implementation. 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