Picture Archiving and Communication systems

Transcription

1 Picture Archiving and Communication systems (PACS) By: Somayeh nabiuni 1

2 Major limitations of the conventional radiology practice Wasted time - implying diagnostic results many not be obtained in a timely manner. High risk of loss or miss filing patient examination data - implying they have to retake the examination With a manual filing system, retrieval time of films from the film library maybe in order of minutes if not hours. Turn around time in obtaining results by the referring physician(s) varies from hours to Days. It is difficult to obtain a copy of the image without the need for the digitized hard copy to be regenerated Consultation among medical personnel Consultation is a very important activity in health care treatment. During this consultation process, information about patients cases and opinions need to be exchanged between attending physicians and specialists. Traditionally, this consultative process occurs through face-to-face meetings, telephone conversation, or a series of written messages passed between physicians. Face to face consultations require both the physician and the specialist be in the same place at the same time. Since physicians and specialists have multiple responsibilities and given the fact that they may be separated by a long distance from the referring physician. This whole process in general turns out to be time-consuming, inefficient and causes delay in patient treatment The limitations of the conventional radiology department and consultation among medical personnel can be solved by deploying a Digital environment Using Picture Archiving and Communication systems (PACS). PACS represents an alternative to film and paper in image interpretation, distribution and management. Based on digital computer technology, a PACS handles images in electronic form with the sole objective of attaining a more efficient and cost-effective means of examining, storing and retrieving diagnostic images. The challenge still facing PACS is clinical acceptance as opposed to traditional practice. Therefore successful implementation of PACS is a complex problem that requires a concerted effort across a wide range of disciplines. Attaining a fully digital environment, will also require the enhancement of PACS for remote consultation or teleconferencing. 2

3 What is PACS? Picture Digital diagnostic image (radiological) Archiving Electronic storage & retrieval (no lost films!) Communication Computer network (multiple access, IS integration) System Control of the processes (integrated technology). 3

4 PACS HARDWARE COMPONENTS Image Acquisition systems Communication Networks Data archive Systems Display workstations The Main Components HIS From Modalities Data Gate Backup RIS PACS Broker Database and Archive Web viewers image Acquisition Systems are composed of medical imaging modalities devices and acquisition gateway computers which interface the imaging devices to the PACS archive server. The role of the Acquisition gateway computer is to: 1. Acquire image data from radiological imaging device 2. Convert the data from the manufacturer s specification to the PACS standard format compliant with the ACR-NEMA/DICOM data formats 3. Perform pre- Image processing functions like background removal, orientation, resizing etc. 4

5 Image Acquisition methods. Two methods are used for image acquisition: Direct digital acquisition and Digitization of plain films. Direct digital acquisition. Recently developed direct X-ray detectors can capture the X-ray image without going through an additional medium like the imaging plate. This method of capture is sometimes called direct digital radiography. Images obtained from 30% of radiology examinations for example CT, NM, MRI, US, DF and DSA are already in digital form when generated making them inherently suitable for PACS integration Digitization of plain films: Since computers can process only digital images, and 70% of the radiology departments still use projection radiology which uses X-ray films a pre requisite for attaining a digital radiology environment is the conversion of the radiolographic images from films to digital format. This is achieved using film/image digitizers like Laser film Scanner and Chargecoupled device (CCD). PACS Network Topology Topology refers to the way the network is laid out physically or logically. Two or more devices connect to a link, then two or more links form a topology. Five basic topologies are possible: Bus, star, tree, mesh and ring.the topologies used depend on the medical environment being network. Conceptually three main types of networks may be used to transport radiology images: 1. A LAN linking imaging devices, data storage units and display devices within one departmental area. 2. A larger LAN for intra-hospital transport linking departments, 3. And a tele-radiology network for transmission of images to other hospitals in the region or to and from remote sites for diagnosis at a distance. 5

6 Data storage and Archive Image storage and communication can be based on either a centralized or distributed architecture. In centralized storage system all the acquired images are forward to a central archive system to which every modality or workstation is attached on a point-to-point basis. Whereas a distributed architecture is composed of linked local storage subsystems or file servers. Each server has its own short-term storage unit (usually a small RAID), one or more image acquisition modalities, and several diagnostic/review workstations. Each of these architectures has it s own advantages and disadvantages. However distributed storage architecture has been found suitable for large-scale PACS and centralized architecture for minipacs. Display Workstation This is the hardware component radiologists compare to the manual light box or Alternator, it therefore plays an important role in the clinical acceptance of PACS. Most radiologists today view diagnostic films in a reading room using light boxes or alternators. Light boxes are lighted panels on which about a dozen films may be hung at a time for inspection and manually rotate about 8 out of 200 films into position for viewing. Using the alternators, rudimentary image processing functions operations like zooming using a magnifying glass and annotation of films is performed. Therefore a display workstation is a replacement of the alternator to provide high quality digital viewing and appropriate image processing capability. The image processing capabilities provided by a display workstation depend on the type of workstation. Some of the basic image processing functions include: Access: Image storage/retrieval, data compression, interpretation of file formats and communication (esp. ACR-NEMA, DICOM), study handling, multiple image display, Manipulation: Image processing operations (e.g. zoom, pan, mirror, contrast/brightness adjustment, reorientation, negate, arithmetics, window/level contrast adjustment), Evaluation: Local/global grey value statistics and geometric properties (2D/3D distance, angle, profile, image annotation..) Documentation: Image annotation, report transcription and hardcopy 6

7 PACS SOFTWARE COMPONENTS Image Acquisition Software responsible for image Acquiring, Formatting, preprocessing, sending, deleting and Archival Archive Server software for image receiving, stacking, routing, study grouping, platter management, retrieving and perfecting. Workstation image processing and analysis software PACS database for patients data storage and organization. It is important to take into consideration defector industrial standards when building PACS infrastructure to enable portability of the system to other computer platforms for example: Windows XP, TCP/IP and DICOM protocols, ZODB as the object oriented database, ACR-NEMA and DICOM for image data format and python as programming language for implementing the PACS. Digital Imaging and Communication in Medicine (DICOM) DICOM is a popular standard which has emerged as a result of the initial efforts by ACR and NEMA joint committee formed in 1993 to: Promote communication of digital image information regardless of device manufacturer Facilitate the development and expansion of PACS that can also interface with other systems of hospital information Allow the the creation of diagnostic information databases that can be interrogated by a wide variety of devices distributed geographically. 7

8 Benefits for clinicians o improved image quality and viewing capability o reduction in time looking for lost images o images available 24 hours a day, seven days a week o simultaneous image viewing across multiple sites and locations o quality images for teaching and presentation Benefits for patients o Easier, secure access to their own health and care information o Faster, safer diagnosis and treatment o Faster, easier, more convenient way to make hospital appointments o Safer way to obtain medication Tertiary Community Acute GP Radiologist at Home 8