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

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Pet dicom format l.jpg

PET DICOM Format

Chunlei Han

Turku PET Centre Sep. 14, 2005, Turku, Finland


Content l.jpg
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


1 1 short history of dicom l.jpg
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


1 2 overview of dicom l.jpg
1.2 Overview of DICOM

DICOM provides

  • Data structure for medical images and related data

  • Network oriented services: image transmission, query of an image archive, pring, modality integration

  • formats for storage media exchange.

  • It is widely accepted as a standard in medical imaging technics.

  • It has become an indispensable component for the integration of digital medical imaging systems

  • 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.


1 3 dicom standard documentation l.jpg
1.3 DICOM Standard Documentation

  • DICOM Part 1: Introduction and Overview

  • DICOM Part 2: Conformance

  • DICOM Part 3: Information Object Definitions

  • DICOM Part 4: Service Class Specifications

  • DICOM Part 5: Data Structures and Encoding

  • DICOM 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/


2 1 attribute structure l.jpg
2.1 Attribute Structure

128 bytes

4 bytes (four characters: ”DICM”)

Data Set Element

Tag

4 bytes

VR

2/4 bytes

ValueLength (VL)

2/4 bytes

Value Field (VF)

defined by VL

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.


2 2 group and element l.jpg
2.2 Group and Element

Tag

4 bytes

VR

2/4 bytes

ValueLength (VL)

2/4 bytes

Value Field (VF)

defined by VL

group number

2 bytes

element number

2 bytes

  • 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,0040,0050,0054,0060,0070,0088,0100,0400,2000,2010,2020,2030,2040,2050,2100,2110,2120,2130,2200, 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.


2 3 value representation and value length l.jpg
2. 3. Value Representation and Value Length

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

VR

2/4 bytes

ValueLength (VL)

2/4 bytes

Value Field (VF)

defined by VL

Tag

4 bytes

A, Explicit VR with reserved. VR is OB, OW, OF, WQ UT or UN

reserved bytes=00000000H

VR

2 byte

Reseved

2 byte

VL

4 bytes

B, Explicit VR without reserved, VR is others.

VL

2 bytes

VR

2 byte

B, Implicit VR (No VR !! ), therefore data set element becomes as

Tag

4 bytes

ValueLength (VL)

4 bytes

Value Field (VF)

defined by VL


Slide9 l.jpg

2.4 Value Field and Others

Value Field (VF)

defined by VL

VR

2/4 bytes

ValueLength (VL)

4 bytes

Tag

4 bytes

Value Field

  • Length is defined by VL.

  • Content format is defined by VR or implicitly.

(0002), (0010) is transfer syntax UID

  • 1.2.840.10008.1.2: implicit VR with little endian

  • 1.2.840.10008.1.2.1: explicit VR with little endian

  • 1.2.840.10008.1.2.2: explicit VR with big endian

    Pixel data is (7FE0), (0010)


2 5 encoding rules l.jpg
2.5 Encoding Rules

  • Skip first 128 bytes for preamble

  • Skip 4 byts for ”DICM”

  • Start to read group and element number

  • first part is always group 0002

  • 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

ValueLength (VL)

4 bytes

Value Field (VF)

defined by VL

Tag

4 bytes

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

ValueLength (VL)

4 bytes

Value Field (VF)

defined by VL

Tag

4 bytes

VR

2 bytes

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

ValueLength (VL)

2 bytes

Tag

4 bytes

VR

2 bytes

Value Field (VF)

defined by VL


3 my plane on dicom l.jpg
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


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