1. PET DICOM Format Chunlei Han Turku PET Centre Sep. 14, 2005, Turku, Finland

2. Content 1. General Introduction 1.1 Short History 1.2 Overview 1.3 Documentation 2. Encoding 2.1 Attribute Structure 2.2 Group and Element 2.3 Value Represention and Value Length 2.4 Value Field 2.5 Encoding Rule 3. My Plan on DICOM

3. 1.1 Short History of DICOM 1970, first CT(computerised tomography) was introduced. Digital medical imaging format emerged. 1985, ACR-NEMA standard was published. 1993, DICOM standard was published and is continuously being extended ever since In 1995, DICOM was accepted as a formal standard in Europe (MEDICOM, ENV 12052). ACR: American Colleg of Radiology NEMA: National Electrical Manufacturers Association DICOM: Digital Imaging and COmmunications in Medicine

4. 1.2 Overview of DICOM DICOM provides 1.Data structure for medical images and related data 2.Network oriented services: image transmission, query of an image archive, pring, modality integration 3.formats for storage media exchange. 1.It is widely accepted as a standard in medical imaging technics. 2.It has become an indispensable component for the integration of digital medical imaging systems 3.It covers almost all the medical imaging devices: such as CT, Ultrosound, X-ray (conventionel, angiographical, dental ect), MRI, PET and even Non-imaging data, such ECG, cardiac electrophysiology and hemodynamic information.

5. 1.3 DICOM Standard Documentation DICOM Part 1: Introduction and Overview DICOM Part 2: Conformance DICOM Part 3: Information Object DefinitionsDICOM Part 3: Information Object Definitions DICOM Part 4: Service Class Specifications DICOM Part 5: Data Structures and EncodingDICOM Part 5: Data Structures and Encoding DICOM Part 6: Data DictionaryDICOM Part 6: Data Dictionary DICOM Part 7: Message Exchange DICOM Part 8: Network Communication Support for Message Exchange DICOM Part 10: Media Storage and File Format for Media Interchange DICOM Part 11: Media Storage Application Profiles DICOM Part 12: Media Formats and Physical Media for Media Interchange DICOM Part 14: Grayscale Standard Display Function DICOM Part 15: Security and System Management Profiles DICOM Part 16: Content Mapping Resource DICOM Part 17: Explanatory Information DICOM Part 18: Web Access to DICOM Persistent Objects (WADO) http://medical.nema.org/

6. 2.1 Attribute Structure 128 bytes 4 bytes (four characters: ”DICM”) Tag 4 bytes VR 2/4 bytes ValueLength (VL) 2/4 bytes Value Field (VF) defined by VL Data Set Element optional field - dependent on negotiated Transfer Syntax Data Element Tag: 4 bytes, hexadecimal, group (2 bytes), elements(2 bytes) Value Represention (VR): optional, 2 or 4 bytes, character, depends on transfer syntax Value Length (VL): 2or 4 bytes, long integer, defines value field length, dependent on VR Value Field (VF): length is defined by VL, format is defined explicitly by VR or implicitly.

7. Tag 4 bytes VR 2/4 bytes ValueLength (VL) 2/4 bytes Value Field (VF) defined by VL Two parts: group (2 bytes) and element (2 bytes), 16-bit unsigned integer, hexadecimal Even number groups (such as 0002, 0008) are called public, definitions are same for all DICOM Odd number groups (such as 0009) are called private, defined by user, but must follow DICOM standard Currently defined public groups 0002, 0004,0008, 0010, 0012, 0018, 0020, 0022, 0028, 0032, 0038, 003A,0040,0050,0054,0060,0070,0088,0100,0400,2000,2010,2020,2030,2040,2050,2100,2110,2120,213 0,2200, 3002,3004,3006, 3008, 300A, 300C,300E,4000,4008,4FFE,50xx, 5200, 5400, 60xx,7FE0,FFFA,FFFC,FFFE Private group examples: GE Discovery conformance defines 0009, 0011, 0013 groups. Special groups 0002 is registry of DICOM file meta elements 0004 is registry of DCOM directory structing elements Special element gggg 0000 defines group length in bytes for all group. group number 2 bytes element number 2 bytes 2.2 Group and Element

8. Tag 4 bytes VR 2/4 bytes ValueLength (VL) 2/4 bytes Value Field (VF) defined by VL VR 2 byte Reseved 2 byte VR 2 byte A, Explicit VR with reserved. VR is OB, OW, OF, WQ UT or UN reserved bytes=00000000H B, Explicit VR without reserved, VR is others. B, Implicit VR (No VR !! ), therefore data set element becomes as Tag 4 bytes ValueLength (VL) 4 bytes Value Field (VF) defined by VL Defined VR: AE: application entiy AS: age string AT: attribute tag CS: code string DA: date DS: decimal string DT: date time FL: floating point single FD: floating point double IS: integer string LO: long string LT: long text OB: other byte string OF: other float string OW: owther word string PN: person name SH: short string SL: signed long SQ: sequence of items SS: signed short ST: short text TM: time UI: unique identifier UL: unsigned long UN: unknown US: unsigned short UT: unlimited text VL 4 bytes VL 2 bytes 2. 3. Value Representation and Value Length

9. Tag 4 bytes VR 2/4 bytes ValueLength (VL) 4 bytes Value Field (VF) defined by VL Value Field 1.Length is defined by VL. 2.Content format is defined by VR or implicitly. (0002), (0010) is transfer syntax UID 1.1.2.840.10008.1.2: implicit VR with little endian 2.1.2.840.10008.1.2.1: explicit VR with little endian 3.1.2.840.10008.1.2.2: explicit VR with big endian Pixel data is (7FE0), (0010) 2.4 Value Field and Others

10. 2.5 Encoding Rules 1.Skip first 128 bytes for preamble 2.Skip 4 byts for ”DICM” 3.Start to read group and element number 4.first part is always group 0002 5.find (0002), (0010), if transfer syntax UID is 1.2.840.10008.1.2: implict VR with little endian, No VR!!, VL is 4 bytes, little endian Tag 4 bytes ValueLength (VL) 4 bytes Value Field (VF) defined by VL 1.2.840.10008.1.2.1/1.2.840.10008.1.2.2: explict VR with little/big endian if VR is OB, OW, OF, WQ UT or UN: No VR!!, VR 2 bytes, reserved is 2 with 00000000H, VL is 4 bytes, and little endian Tag 4 bytes VR 2 bytes ValueLength (VL) 4 bytes Value Field (VF) defined by VL reserved 2 bytes if VR is SQ: go to encode by rule of sequence if VR is, others: VR is 2 bytes and VL is also 2 bytes Tag 4 bytes VR 2 bytes ValueLength (VL) 2 bytes Value Field (VF) defined by VL

11. 3. My Plane on DICOM DICOMReader (finished) for general and specific modality, such as GE Advance PET, GET Discovery PETCT and Philips MRI DICOM2ECAT7 (almost finished) PETCT Viewer (finished) DICOMModifer, rename and anonymyous DICOMWriter and ECAT7toDICOM DICOM Viewer and ROI tookit