DICOM Digital Imaging and Communications in Medicine

Transcription

1 DICOM Digital Imaging and Communications in Medicine INF5081 / Vårsemester 2007 Wolfgang Leister Reidar Øksnevad Pedro Cruz G. April 2007 PACS PACS = Picture Archive and Communication System Archive for medical imaging Data exchange / tele-radiology Modality = imaging device ultrasonography, magnetic resonance imaging, positron emission tomography, computed tomography, endoscopy, mammography, radiography (X-rays),... Other information systems in health care HIS = Hospital Information System RIS = Radiology Information System IHE = Integrating the Healthcare Enterprise (e.g., HL7)

2 PACS Picture Archiving and Communication Systems Medical systems hardware and software run digital medicine workflow. Archiving servers Diagnostic workstations, Integrated with digital image acquisition devices. Based on DICOM DICOM Digital Imaging and Communications in Medicine Major standard for medical imaging. Developed by NEMA National Electrical Manufacturers Association in cooperation with international organizations. «huge» standard, continuously evolving. Companies participate in the process. Most big manufacturers of medical equipment supports DICOM. All hospitals in Norway use DICOM for medical image communication.

3 Why DICOM? Needed an open standard for image communication between medical imaging hardware / software e.g., CT, ultrasound, etc. Hospitals / doctors / dentists countries The DICOM standard Industry-Standard Divided into several parts: Conformance statement «DICOM compliance» stating what part of the standard is implemented optional components

4 The DICOM standard Networking A protocol on top of TCP/IP Higher-level networking (syntax, semantics) between PACS An offline file format Archive on CD or DVD Printing... Send Print Class/Instance SOP 8

5 DICOM History Based on ACR-NEMA standard published in ACR (American college of radiology) NEMA (National Electrical Manufacturers Association) DICOM was established in Nearly annual updates Many supplements DICOM 2007 contains 18 parts and 133 supplements DICOM Base Standard 2007 PS 3.1 Introduction and Overview PS 3.2 Conformance PS 3.3 Information Object Definitions PS 3.4 Service Class Specifications PS 3.5 Data Structures and Encoding PS 3.6 Data Dictionary PS 3.7 Message Exchange PS 3.8 Network Communication Support for Message Exchange PS 3.10 Media Storage and File Format for Data Interchange PS 3.11 Media Storage Application Profiles PS 3.12 Media Formats and Physical Media for Data Interchange PS 3.14 Grayscale Standard Display Function PS 3.15 Security Profiles PS 3.16 Content Mapping Resource PS 3.17 Explanatory Information PS 3.18 Web Access to DICOM Persistent Objects (WADO)

6 DICOM Parts (as of 2003) Part 1: Overview Part 2: Conformance Part 4: Service Class Specifications Part 5: Data Structures and Semantics Part 6: Data dictionary Part 7: Message exchange Part 10: Media Storage & File Format (Network operations) Part X Part Y Part Z Part 8: Net- Work Support TCP/IP & OSI Part 9: Point to Point Part 3: Information Objects Part 11: Media Storage Application Profiles Specific Media formats & Physical Media PARTS OF DICOM V3 Extensions to DICOM to support media storage How DICOM works Information Objects = objects in DICOM Service Classes = operations and services Instance = use of a service class e.g., CT-Store

7 The DICOM File Format Header containing the patient's name / id type of media (CT, MRI, audio recording, etc.) image dimensions... Body, containing «information objects» medical reports audio recordings images A Typical DICOM Image File

8 Images in DICOM files A single DICOM file can contain any number of images. The format needs to be specified in the header: native, as defined in the standard: raw data lossless JPEG, RLE or LZW lossy JPEG an encapsulated format: JPEG2000 (JPEG2000-3D) MJPEG for animations MPEG-4 JPEG2000 in DICOM Accepted by NEMA in 2001 Lossless or lossy coding Resolution scalability

9 JPEG2000 in DICOM Region of Interest Encoding in JPEG2000 use lossless compression on the important parts of an image code the less important parts using a lossy algorithm Original image Image with encoded with ROI Communication Protocol in DICOM Medical Imaging Application DICOM Application Message Exchange DICOM Session/ Transport/ Network STN DICOM Upper Layer Protocol for TCP/IP OSI Association Control Service Element (ACSE) OSI Presentation OSI Session DICOM Data Links TCP OSI Transport DICOM IP OSI Network Physical Point to Point Enviroment Standard Network Physical Layers (Ethernet, etc). Network Enviroment 18

10 Important things to know JPEG 2000 is now the official compression method under DICOM. Wavelet based, up to 16-bit pixel depth. Lossless and lossy. DVD is now an official exchange medium under DICOM Can use any DVD flavor (-ROM, +R, +RW, etc.) Reader most support JPEG or JPEG 2000 lossy compression New work under way to Endoscopy Visible Light Video (endoscopy, microscopy, photography). MPEG video image encoding in DICOM!. Schemes supported by DICOM JPEG : lossless and lossy. Lossy JPEG for ultrasound Multiframe 512x512x8, 1024x1024x10 CD-R and on network BUT JPEG lossy limited to 12 bits unsigned! JPEG-LS: More efficient, fast lossless. Lossless JPEG for cardiac angio: 640x480 single and multiframe 8 bits gray/rgb, text BUT JPEG lossless not the most effective! Deflate ( gzip-zip ): For non-image objects. JPEG 2000: Progressive. Added to DICOM the 14th. of January 2002.

11 Conclusion DICOM is an image file format a networking protocol built on TCP. Major standard for digital medical applications handling medical data and images. DICOM has several parts which describe the procedures of the digital object to analyze. DICOM is constantly evolving hard to conform!!! PACS (hardware and software) and DICOM are closely related. References great introduction to the DICOM file format has «everything» image samples the official standard PACS information