MEDICAL IMAGING INFORMATICS Dr. Ali M. Hadianfard Faculty member of AJUMS http://www.alihadianfard.info/download.html
Further reading • Biomedical informatics computer applications in health care and biomedicine (3rd edition), Edward H. Shortliffe, 2006 (chapters 9 and 18). • PACS and Imaging Informatics Basic Principles and Applications (2nd edition), H. K. Huang, 2010 (chapters 1 and 7). • PACS A Guide to the Digital Revolution, Keith J. Dreyer, David S. Hirschorn, James H. Thrall, Amit Mehta, 2010 (chapter 2)
What is medical imaging informatics? Because of increasing availability of medical images in digital form, medical digital images have become a core data type that must be considered in many biomedical informatics applications. It is a subfield of biomedical informatics that has arisen in recognition of the common issues that pertain to all image modalities and applications once the images are converted to digital form. Medical imaging informatics embraces the following areas: Image Generation : The process of generating the images and converting them to digital form if they are not intrinsically digital ImageManipulation: Uses pre-processing and post-processing methods to enhance, visualize, or analyze the images ImageManagement :Includes methods for storing, transmitting, displaying, retrieving, and organizing images ImageIntegration : The combination of images with other information needed for interpretation, management, and other tasks (e.g. Patient record)
Why medical imaging is important? Diagnosis (Detection) Treatment planning Image-guided treatment, e.g. Image-guided surgery produced minimally invasive surgery Assessment of response to treatment Estimation of prognosis Medical communication Education Research
Medical imaging progress over time 1980s:Medical imaging technology development Computed radiograph(CR), MRI, CT, Ultrasonography(US), Digital Radiography(DR), WS, storage, networking Late 1980s: Imaging systems integration • PACS, the American College of Radiology and the National Electrical Manufacturers Association (ACR/NEMA), DICOM, high-speed networks Early 1990s: Integration of HIS/RIS/PACS • DICOM, HL7, Intranet and Internet Late 1990s–present:Workflow and application servers •Integrating the Healthcare Enterprise (IHE), ePR, enterprise PACS,Web-based PACS 2000s–present: Imaging informatics • Computer-aided diagnosis (CAD), image contents indexing, • Knowledge base, decision support, • Image-assisted diagnosis and treatment
Parameters of image quality Spatial resolution :Is related to the sharpness of the image; the number of pixels (voxels) per image area. Contrast resolution:Is a measure of the ability to distinguish small differences in intensity; the number of bits per pixel Temporal resolution:Is a measure of the time needed to create an image
Energy sources to create images Light X-rays: fluoroscopy, CT scan Ultrasound: Ultrasonography Nuclear Magnetic Resonance: MRI, positron-emission tomography (PET) - nuclear-medicine imaging e.g. radioactive isotope
What is PACS? A Picture Archiving And Communication System (PACS) consists of medical image and data acquisition, storage, and display subsystems integrated by digital networks and application software.
PACSInfrastructure PACS infrastructure consists of a basic skeleton of: hardware components (imaging device interfaces, storage devices, host computers, communication networks, and display systems) integrated by : a standardized, flexible software system for communication, database management, storage management, job scheduling, inter-processor communication, error handling, and network monitoring.
PACSComponents • Data and Image Acquisition Gateways • PACS Server and Archive • Display Workstations (Diagnostic and Review) • Application Servers • System Networks
Data and Image Acquisition Gateways PACS acquires images sent from imaging modalities (devices) and related patient data from the hospital information system (HIS) and the radiology information system (RIS). There are two types of gateways (GW) to the PACS server and archive, the database GWfor textual data, and the image acquisition GWfor imaging data. A major task in PACS is to acquire images reliably and in a timely manner from each radiological imaging modality via the acquisition GW, and relevant patient data, including study support text information of the patient, description of the study, and parameters relevant to image acquisition and processing through the database GW.
Major functions of the PACS Server and Archive • Receives images from examinations (exams) via acquisition gateways • Extracts text information describing the received exam from the DICOM image header • Updates the database management system • Determines the destination workstations to which newly generated exams are to be forwarded • Automatically retrieves necessary comparison images from historical exams from a cache storage or long term library archive system • Automatically corrects the orientation of computed or digital radiography images • Determines optimal contrast and brightness parameters for image display • Performs image data compression if necessary • Performs data integrity check if necessary • Archives new exams onto long-term archive library • Deletes images that have been archived from the acquisition gateway • Services query/retrieve requests from WSs and other PACS controllers in the enterprise PACS • Interfaces with PACS application servers
Major functions of PACS workstations • Case preparation: Accumulation of all relevant images and information belonging to a patient examination • Caseselection: Selection of cases for a given subpopulation through DICOM query/retrieve • Imagearrangement: Tools for arranging and grouping images for easy review • Interpretation: Measurement tools for facilitating the diagnosis • Documentation:Tools for image annotation, text, and voice reports • Casepresentation: Tools for a comprehensive case presentation, including 3-D image display for a large 3-D file, and fusion images • Imagereconstruction: Tools for various types of image reconstruction for proper display
Application Servers Application servers are connected to the PACS server and archive. Through these application servers, PACS data can be filtered to different servers tailored for various applications.
System Networks A basic function of any computer network and protocol (TCP/IP) are to provide an access path by which end-Users. At the local area network level, digital communication in the PACS infrastructure design can consist of low-speed Internet (10 Mbits/s signaling rate), medium-speed (100 Mbits/s) or fast (1 Gbit/s) Internet, and high-speed asynchronous transfer mode technology (ATM, 155–622 Mbits/s and up). In wide area networks, various digital service (DS) speeds can be used, which range from DS-0 (56 kbits/s) and DS-1 (T1, 1.544 Mbits/s) to DS-3 (45 Mbits/s) and ATM (155–622 Mbits/s).
System Networks – continue A low-speed network is used to connect the imaging modalities (devices) to the acquisition gateway computers because the time consuming processes of imaging acquisition do not require high-speed connection. Medium and high-speed networks are used on the basis of the balance of data throughput requirements and costs. A faster image network is used between GWs and the PACS server because several GWs may send large image files to the server at the same time. High-speed networks are always used between the PACS server and WSs.
Compression methods • Lossless compression: Maximum compression ratios achievable with lossless methods are on the order of 2:1 or 3:1. • Lossycompression: Compression ratios as high as 20:1 can be obtained with JPEG compression, but with variable quality. • Wavelet compression: Wavelet compression at ratios as high as 80:1 for plain films such as mammograms have being evaluated, and found to be satisfactory, although ratios of more than 60:1 are rarely used.( in the JPEG 2000 standard) (اصول موجك، مجموعه ايازموجهاستكه توسط مقياسهايي از موجكمادر بدست می آیند.)