Transcript Document
PACS COMPONENTS, STANDARDS AND THEIR IMPLEMENTATION IN A PROTOTYPE APPLICATION. A Dissertation submitted in partial fulfillment of the requirements for the award of Masters degree in Computer Applications. By: Francis Batte Supervised by: Dr. Chen Tianzhou Department of Computer Science, Zhejiang University. Structure of this thesis PART 1 Chapter 2.0 PACS Hardware Architecture Chapter 1.0 Introduction. Chapter 3.0 PACS Software Architecture Chapter 4.0 DICOM Figure 1.3 Structure of this Thesis. PART II Chapter 6.0 WebXray Remote Consultation Tool Chapter 7.0 Conclusions Recommendations . Chapter 5.0 Prototype PACS Application Thesis outline • • • • • • Introduction PACS Hardware Components PACS Software Components DICOM PACS Prototype Application WebXray Real-time Teleconsultation Tool. Examination cycle in a conventional radiology Department Examination Request X-Ray LabPatient Reading Room Film Library RODIOLOGY DEPARTMENT Turn around may vary from Hours to days. Specialist Wards Referring Physician Intensive care Units Operating Rooms Emergency Department Radiologist Clerk Radiologist’s Report Transcription Office -Clerk Types out the report Problem Analysis Other hospital Departments Outside clinics 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. Problem Anaysis 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. Problem Analysis • 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. What are PACS? According to National Electrical Manufacturers’ Association (NEMA), a PACS should be able to offer: • Medical image viewing at diagnostic, reporting, consultation and remote workstations, • Archiving on magnetic or optical media using short or long-term storage devices, Communication using local or wide area networks or public communications services, • Systems integration with other healthcare facility for example image acquisition modalities, gateway computers and departmental information systems. 8 PACS HARDWARE COMPONENTS • • • • Image Acquisition systems Communication Networks Data archive Systems Display workstations Image Acquisition Systems are composed of medical imaging modalities’ devices and acquisition gateway computers which interface the imaging devices to the PACS archive server as illustrated in the figure below. NM, DSA, US, CR, or MR Imaging Acquisition Device/modality To Archive or DWS Acquisition Gateway Computer Interface Mechanism DWS = Display Workstation Fig 2.1: Schematic block diagram showing PACS image acquisition, with an interface mechanism connecting the imaging device to the acquisition gateway computer. The role of the Acquisition gateway computer is to: • Acquire image data from radiological imaging device • Convert the data from the manufacturer’s specification to the PACS standard format compliant with the ACR-NEMA/DICOM data formats • Perform pre- Image processing functions like background removal, orientation, resizing etc. 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 Charge-coupled device (CCD). Communication networks PACS communication networks enable the movement of medical data between modality imaging devices, gateway computers, PACS server, display workstations, remote locations for diagnosis and consultation and other Hospital information systems like HIS/RIS. The most commonly used network technologies in building PACS networks are: • The Ethernet based on IEEE standard 802.3, Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol. Suitable for LANs and can operate at 10Mbits/Sec on half-inch coaxial cable, twisted pair wire or fiber optic cables. • FDDI can be used for medium speed communication. Runs on optic fiber at 100Mbits/sec over a distance of 200kms with upto 1000 stations connected. • ATM: Can be used to combine LAN and WAN application. ATM is a Virtual circuit- oriented packet switching network with transmission speed ranging from 51.84 Mbits/sec – 2.5 Gbits/sec. 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: • A LAN linking imaging devices, data storage units and display devices within one departmental area. • A larger LAN for intra-hospital transport linking departments, • 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. 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. Local storage Imaging Device Acquisition Server Acquisition Computer To Remote Sites. Network connection ATM Switch L Local Workstation PACS Central Archive System (Controller) Figure 2.4: Storage subsystems in a distributed large scale PACS. Display Server. Storage Media PACS storage devices should hold gigabytes of data with relatively efficient access time. Research continues to consistently improve PACS by providing storage media that can hold many images and have quick access time. A PACS needs at least two levels of archive (short-term and longterm). Images should be retrievable from the short-term archive in 2 seconds. Images from the long-term archive should take no more than 3 minutes to retrieve. Examples of storage media that can be used for PACS archiving include: • Redundant array of inexpensive disks (RAID) for immediate access of current images. • magnetic disks for faster retrieval of cached images, • erasable magneto-Optical disks for temporary long term archive, • write once read many (WORM) in the optical disk library, which constitute the permanent archive, • Recently developed digital versatile discs (DVD-ROM) for low cost permanent archive • And the digital linear tapes for backup storage 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 greyvalue statistics and geometric properties (2D/3D distance, angle, profile, image annotation..) Documentation: Image annotation, report transcription and hardcopy, PACS Software Components. PACS software is composed of various software modules performing different functions depending on the size of the PACS Application. For Example: • 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 prefetching. • Workstation image processing and analysis software • PACS database for patients’ data storage and organization. Industrial standards • It is important to take into consideration defacto industrial standards when building PACS infrastructure to enable portability of the system to other computer platforms. For example the following industrial standards should be used in a PACS infrastructure design: UNIX operating system, Windows NT, TCP/IP and DICOM protocols, SQL (Structured Query language) as the database query language, ACR-NEMA and DICOM for image data format, HL7 for database information exchange between PACS, HIS and RIS. 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. • Since it’s inception, DICOM 3.0 has gone through a lot of modifications and additions, the latest version released in 1998, consists of 14 parts identified by numbers PS 3.X – YYYY where X is part number and YYY is year of release (see Appendix A). • For example PS 3.2 (Conformance statement) describes how a manufacturer’s device or its associated software components conform to a subset of DICOM standard. A device or software needs only to conform to a subset of DICOM to be DICOM compliant. For example a Laser film digitizer needs to conform only to the minimum requirements for the digitized images to be in DICOM format and the digitizer should be a service class user to send the formatted images to a second device (e.g. magnetic disk), which is a service class provider. WEBXRAY APPLICATION. annotation tool image tool Graphics format tool Database computer aided diagnoses tools SQL network supported computer aided diagnoses tools information query and case tree other operation ut inp nettalk output dicom file tool USER INT ERFACE Menu and Toolbar Display Forms scanner tool dicom display tool display print tool printer Database Design WebXray Database is an object oriented database model implemented using SQL server 7.0, running on Windows NT operating system. The database is broken down into three components. • Storage system • Storage Management • Case Tree The Schematic diagram summaries the design architecture of the WebXray database. User Interface Case Display Form Items Display Form Image display Form Sql Database manger Case Tree Case Table Items T able Image Table Stoarge system Storage System Contains three tables • Case table containing patient’s demographic and registration information: Attributes in the table include Patient’s ID, name, sex, birthday, address and Case_ID as primary key • Items table stores patients’ diagnosis information after examination: Attributes in the table include inspection cause, date, site, diagnosis result, doctor and date with Items_ID as the primary key • Image table stores image data and related information i.e Image_ID, title, View result, annotation. Schematic diagram showing Data capture and table relationships Patient Doctor takes Images Image Data Capture Diagnosis Capture Patient Information Capture Stored Case Table Stored Image Table Stored Items T able 1 Case_ID ............. ................ ................ ................ ................. Diagnosis Contains Diagnosis 1 n Items_ID Case_ID ................ ................ .................. ................... n Image_ID Items_ID ................ ................... ................... .................... • Storage management is performed by Stored procedures implemented in the SQL server script, enable updating, querying and client server communication with the database. Stored procedures are used in this case as opposed to the execution of similar queries activated from the client to reduce network traffic. • Case Tree The case tree, the front-end hierarchical Tree View of the database embedded in the Graphical User Interface. It facilities the communication between the user and the SQL database server during database manipulation and image display. With the case tree it is possible to switch between the 3 database forms easily in the Graphical user interface to enter new data or view existing data DICOM Compatibility DICOM File tool. • WebXray acquires DICOM images through DICOM CDROMs, CD-ROMs specifically designed for medical application. WebXray uses DICOM single file format. A single DICOM file contains a file header and the actual image data. (see appendix B for WebXray DICOM header) • TDICOMObject is used in WebXray to open and read the DICOM file stream into memory and to convert the memory stream from DICOM format to BMP for display on the workstation. (page 48/49). DICOM Display tool Demonstration of the DICOM display Tool Effect on the same image using different window level settings. Computer aided diagnosis tools. • These tools are incorporated into the user interface to aid image processing and analysis. They include: Graphics format tool for annotation of images with text and graphics symbols during image analysis. Annotations help doctors isolate regions of interest on the image for further examination. Image Tool • This tool has most of the image processing tools mention earlier: Image scanning, zooming, loading, geometric transformation, smoothening, sharpening and displaying the edges of the image e.t.c Graphical User interface Design • In addition to the case tree, image tool and graphics tool already mentioned earlier, the Graphical User Interface has additional features like: Menu Bar, Toolbar and three forms used to enter, edit, manipulate and display the patient’s data stored in the database. Figure shows the image form used to display and manipulate data in the Image table. WebXray Hardware requirements • A Server with: CD-R, at least 64MB of RAM, Windows NT operating system and MS SQL Server for database management. • CD-ROMS for short term and long term archiving • High resolution Pentium computers with memory not less than 64MB as Clients. • Digital film scanner for digitizing X-ray films. • Laser printers for producing a hard copy diagnosis report and conference notes • 10 M/bits Ethernet or better . WebXray Real-time Teleconsultation Tool. • Consider the scenario: A doctor in a hospital ward wants to consult the radiologist about the results written for one of the patients in the ward, without having to leave the ward and walk all the way to the radiology department. This is one of the many scenarios teleconsultation is trying to address. Teleconsulation is a situation in which two or more physicians located in different departments of the hospital or geographically dispersed need to discuss the same patients’ image data without leaving their locations. Simple solutions have come up like Televideo and application sharing software for example NetMeeting from Microsoft, Proshare by Intel, PC Anywhere by Symantec and many others but have found little applicability to the medical environment due to lack of image processing tools. This therefore calls for integration of the teleconsultation component component with medical imaging component. This can be achieved in several ways each with its distinct advantages and disadvantages: 1) Conventional application-sharing software could be used in conjunction with PACS software. This can be realized first but will have poor performance as already mention above. 2) A CSCW toolkit can be used to add the communication functionality to existing medical imaging software. This may have draw back because of lack of total integration of the two of software 3) A PACS medical imaging software can be created from the ground up with the communication facilities built in. This option is more complex but provides optimal performance since all the system components will be fully integrated into the system. In our system we adopt the third approach to develop the webXray remote consultation tool (referred to as Nettalk) by adding communication functionality to the WebXray application using TCP/IP. The purpose of adding Nettalk in the WebXray PACS application is to enable physicians’ exchange comments in real-time during a tele-consultation session. In addition to the above, the application provides: A friendly multi-user graphical interface, containing a user menu and toolbar to quickly access commonly used commands. Shared Text view visible to all conference participants and a private text editor for posting text to the conference. Client/server communication using TCP/IP. Print facility to enable printing conference notes Basic software functions like save, open , print preview. Etc.. Nettalk Communication Design • Nettalk is based on a replicate model for client-server process communication. In a replicate model each participating site runs a copy of the conferencing software with identical functionalities. Any conferencing data generated by a participating site will be disseminated to other participating sites and maintained locally. The replicate model has striking advantages such as better system performance, that is why it is chosen as the implementation model for nettalk. • TCP/IP protocol is used in implementing client-server communication architecture. In client-server communication architecture, communication generally takes the form of a request message from the client to the server asking for a service to be delivered. The server then processes the service and sends back a reply Illustration of client-server model using TCP/IP as the communication protocol. request Client process TCP?IP Reply Server process • To add TCP/IP functionality to nettalk, client/server sockets are used. Delphi provides two VCL (Visual Component Library) classes, TClientSocket and TServerSocket, which allow creating TCP/IP socket connections to communicate with other remote applications. • TserverSocket. TServerSocket is used to manage server socket connections for TCP/IP server. TServerSocket object is added to nettalk design form to turn it into a TCP/IP server. When the application is running, TServerSocket listens for requests from TCP/IP connections from remote machines, and establishes connections when requests are granted. • TclientSocket. TClientSocket is used to manage socket connections for TCP/IP client. TClientSocket object is added to nettalk design form to turn it into a TCP/IP client. TClientSocket specifies a desired connection to nettalk TCP/IP server, manages the connection when it is open, and terminates the connection when the application is through. SendText and ReceiveText Some of the main procedures I used in this program to activate socket connections are sendText and receiveText. • SendText: function SendText(const S: string): Integer; This procedure writes a string S to the socket connection • ReceiveText: function ReceiveText: string; ReceiveText is used to read a string from the socket connection in the OnClientRead event handler of a socket component For Example ……. for j:=0 to i do serversocket1.Socket.Connections [j].SendText (label1.Caption+': ' +edit1.text); edit1.Clear; end; Will broadcast to all connected sections the text in sendtext() Discussions, conclusions and Future Work • • • Future advances PACS in workstation display resolution, network speed, data storage capacity, computer speed and electronic components will help make PACS a powerful alternative to Hard-copy system. From this research in chapters 2 through 3 it is realized that building PACS demands a lot in terms of hardware and software and depends greatly on the currently available technologies. Therefore in a mid of limited resources, the computerization process in hospitals should be stepwise, first hospitals need to set up RIS and HIS which are less demanding before setting up PACS. Mini PACS with the possibility for expansion can be a hopeful solution for small radiology departments . Chapter 5.0 analyzed the implementation of PACS components in a prototype application (WebXray). WebXray is implemented on the Windows NT operating system platform because Windows NT is the most widely used network operating system running on PCs and support TCP/IP communication and multitasking. It therefore provides a low cost software development platform for medical imaging applications in a PC environment. • Chapter 6.0 is an effort we adopted to address the problem of consultation among medical personnel. To enable referring physicians use WebXray for Remote consultation, Nettalk was developed. With nettalk, unlimited number of referring physicians can easily exchange comments with their colleagues scattered in different parts of the hospital while analyzing the same image, bridging space and time very critical in health care delivery. • However, WebXray needs more enhancements to be a full medical multimedia conferencing system. More program modules need to be added to support exchange of graphic annotations, voice and video, which this research was not able to accomplish in a limited time frame. MY SINCERE THANKS TO THE DEFENSE COMMITTEE AND EVERYONE PRESENT FOR SPARING YOUR VALUABLE TIME TO ATTEND THIS PRESENTATION.