DICOM: Definitions and Testing

(1)

DICOM:

Definitions and Testing

Bruce Curran Bruce Curran University of Michigan University of Michigan (AAPM Representative, DICOM WG (AAPM Representative, DICOM WG--77

Walter R. Bosch Walter R. Bosch Advanced Technology Consortium Advanced Technology Consortium Washington University of St. Louis Washington University of St. Louis

Acknowledgements

Sam Brain, Stanford University

Stanford IMRT Short Course Stanford IMRT Short Course

Committee to Advance DICOM

Slide Resources Slide Resources

DICOM Working Group 7

Radiation Therapy Extensions Radiation Therapy Extensions

Objectives

Introduction to

Introduction to ‘

‘DICOM

DICOM-

-speak

speak’

’

History of DICOM History of DICOM Overview of Documentation Overview of Documentation

DICOM Testing

Conformance Statements Conformance Statements DICOM

DICOM ‘‘AuthoritiesAuthorities’’ Some useful DICOM Utilities Some useful DICOM Utilities

Use of DICOM in National Protocols

DICOM

DICOM Connectathon

Connectathon

What is DICOM?

D

igital I

igital

I

maging CO

maging

CO

mmunications

in M

in

M

edicine

Network/Communication Protocol

Designed for transfer of information Designed for transfer of information Initial shortcomings for storage, management Initial shortcomings for storage, management

Object

Object-

-Oriented Model

Oriented Model

Abstracts processes based on the data Abstracts processes based on the data

Images, Plans, Structure Sets

Operators are actions that act on the data Operators are actions that act on the data

Storage, Query, Print

(2)

Network Protocol

LLC ISO NETWORK ISO TRANSPORT ISO SESSION KERNEL ISO PRESENTATION ISO Association Control Service Element (ACSE)

TCP IP DICOM Upper layer protocol for TCP/IP Session / Transport / Network (STN) Data Link Physical

(50-pin) Ethernet, FDDI, ISDN, etc. DICOM Application Entity Medical Imaging Application ISO Upper

Layer Service boundary

Point-to-point Network Environment

DICOM Features

OBJECT DATA MODEL

DICOM is based on a completely specified data model

DICOM includes a robust UID mechanism

DATA DICTIONARY

DICOM includes a large number of new data elements

SERVICE CLASSES

DICOM defines classes of service for specific

applications (e.g. image management, printing) and

conformance levels conformance levels

DICOM Features

NETWORK PROTOCOL

DICOM incorporates

DICOM incorporates negotiationnegotiationto permit nodes to agree to permit nodes to agree

on the functions to be performed

MESSAGE ENCODING

DICOM defines 24+ data types

DICOM message encoding includes JPEG compression

DICOM includes encapsulated image and multi

DICOM includes encapsulated image and multi--frame frame

syntaxes

DICOM supports multiple character repertoires

DICOM Features

Off

Off-

-Line Media Support

Line Media Support

DICOM defines a directory structure and media profiles

CD

CD--ROM, DVD, ROM, DVD, ……

Conformance

DICOM requires conformance statements and contains

detailed conformance requirements

Means of Testing, establishing compatibility

(3)

DICOM Terminology

DICOM Message Service Element (DIMSE)

-

The set The set of DICOM Application Layer communication services.

of DICOM Application Layer communication services. DIMSE Service Group (DSG)

DIMSE Service Group (DSG)

-

A subset of the full A subset of the full

DIMSE services which is applicable to a specific IOD.

DIMSE services which is applicable to a specific IOD. Information Object Definition (IOD)

Information Object Definition (IOD)

-

A data A data abstraction of a class of real

abstraction of a class of real--world objects. A collection of world objects. A collection of

related attributes (data elements).

DICOM Terminology

Service Class

-

A set of functionality relating to a A set of functionality relating to a

single type or real

single type or real--world activity. Composed of a set world activity. Composed of a set

of SOP Classes plus rules and associated semantics.

of SOP Classes plus rules and associated semantics. Service

Service--ObjectObject--Pair Class (SOP)Pair Class (SOP)

-

The atomic The atomic

unit of DICOM functionality. Composed of an IOD

and a DIMSE Service Group plus restrictions or

extensions of the IOD. (Equivalent to an Object

Class)

Service

-

Object Pair Class

SOP

Data Dictionary

Real

Real--World ObjectWorld Object

Information Object

Information Object DIMSE Service GroupDIMSE Service Group

DICOM Service Classes

Verification Verification Storage Storage Query/Retrieve Query/Retrieve Print Management Print Management Patient Management Patient Management Study Management Study Management Results management Results management Study Content Study Content Notification Notification

(4)

DICOM Service Classes

Verification (C

-

ECHO)

SCU (client) sends a C

SCU (client) sends a C--ECHO request to SCP ECHO request to SCP (server)

(server)

SCP replies with C

SCP replies with C--ECHO response back to SCUECHO response back to SCU DICOM equivalent of Unix

DICOM equivalent of Unix ““pingping””, but occurs , but occurs between DICOM AE

between DICOM AE’’ss

DICOM Service Classes

Storage (C

Storage (C--STORE)STORE) a.k.a.

a.k.a. ““pushpush””

Transfer is initiated at

the SCU (client)

SCP (server) stores

DICOM objects on

some medium (disk,

etc.) etc.) MAGN ETOM LiteBox SCU SCP STORE

DICOM Service Classes

Query/Retrieve

Query/Retrieve a.k.a.

a.k.a. ““pullpull””

Service has two parts

Service has two parts SCU makes a request for list of

SCU makes a request for list of

available objects (FIND)

SCU then requests the images

transferred back to self (GET)

or... or... LiteBox SCP SCU MAGN ETOM DB FIND GET

DICOM Service Classes

Query/Retrieve

Query/Retrieve a.k.a.

a.k.a. ““pullpull”” Service has two parts

Service has two parts SCU makes a request for list of

SCU makes a request for list of

available objects (FIND)

SCU then requests the images

transferred back to self (GET)

transferred back to self (GET)……

…

…or to another W/S (MOVE)or to another W/S (MOVE)

LiteBox SCP SCU MAGN ETOM DB FIND MOVE LiteBox

(5)

DICOM Service Classes

Print Management

Print Management Prints to DICOM

Prints to DICOM--capable capable N/W printer or W/S with local

N/W printer or W/S with local

printer

Allow printing of images and

overlays

Layout and gray scale control

Queue management Queue management SCP SCU MAGN ETOM N/W Printer LiteBox LiteBox Printer

How can I make DICOM work?

Configuration

Application Entity Title (AETITLE) Application Entity Title (AETITLE)

Name for a DICOM Sender / Receiver

Maximum of 16 characters, typically all caps

Maximum of 16 characters, typically all caps IP Address / Host Name

IP Address / Host Name

How to find the DICOM Application in TCP/IP Land

How to find the DICOM Application in TCP/IP Land Port

Port

TCP/IP mechanism for defining/restricting access

DICOM can use any port, 104 is specifically allocated

What Happens in DICOM?

MAGN ETOM LiteBox • Establish an Association • Location • Find IP/Host • Port must be active • Negotiation

• SOP Available • Data Formats • Perform the Service

• Transfer Data for Storage • Close the Association

SERVICE CLASS USER (SCU) SERVICE CLASS PROVIDER (SCP)

DICOM Communication

Network Data Transfer

Negotiated syntax Negotiated syntax

Big/Little

Big/Little--endianendian

What Services are supported

JPEG Compression JPEG Compression LiteBox LiteBox “Can you…?” “Yes, I can.” DICOM DICOM

(6)

Departmental Data Flows

MAGN ETOM MAGN ETOM LiteBox LiteBox CT MR DB Archive Virtual Sim. (AcqSim) RTP Linac Simulator Image SS, Plan, Dose Image

Image All Image

Plan Image, SS, Plan SS, Plan, Image Image LiteBox Portal Imaging

DICOM Data Stream

Data Element Data Element Data Element Data Element

…

Tag VR Value

Length Value Field Data Set

Optional - Dependant on Transfer Syntax

Order of Transmission

DICOM Data Elements

Name is unique label

(See Part 6)

VR is data type

Defined in Part 5

Tag is unique ID

(2) 4-digit (hex) numbers Defined in Data Dictionary (See Part 6)

1st_{number is group}

Even is Standard Odd is Private Extension Table C.7.2.1 -- General Study Module Attributes

Attribute Name Tag Type Attribute Description Study Instance UID (0020,000D) 1 Unique identifier for the Study. Study Date (0008,0020) 2 Date the Study started. Study Time (0008,0030) 2 Time the Study started. Referring Physician's Name (0008,0090) 2 Patient’s referring physician Study ID (0020,0010) 2 User or equipment generated Study

identifier. Accession Number (0008,0050) 2 A RIS generated number which

identifies the order for the Study. Study Description (0008,1030) 3 Institution-generated description or

classification of the Study (component) performed. Name of Physician(s) Reading

Study (0008,1060) 3 Physician(s) reading the Study.

DICOM Tags

Types

1 Required, non-blank 2 Required, can be blank 3 Optional

Description Description

Free text description of

attribute

Table C.7.2.1 -- General Study Module Attributes Attribute Name Tag Type Attribute Description Study Instance UID (0020,000D) 1 Unique identifier for the Study. Study Date (0008,0020) 2 Date the Study started. Study Time (0008,0030) 2 Time the Study started. Referring Physician's Name (0008,0090) 2 Patient’s referring physician Study ID (0020,0010) 2 User or equipment generated Study

identifier. Accession Number (0008,0050) 2 A RIS generated number which

identifies the order for the Study. Study Description (0008,1030) 3 Institution-generated description or

classification of the Study (component) performed. Name of Physician(s) Reading

(7)

DICOM RT

Proposed at RSNA, 1994 Proposed at RSNA, 1994

Working Group started in 1995 as NEMA RT Section TG

First objects approved in 1998

Added several objects for Radiation Therapy Added several objects for Radiation Therapy

RT Dose RT Dose RT Structure Set RT Structure Set RT Image RT Image RT Plan RT Plan RT Treatment

RT Treatment Record(sRecord(s))

Since DICOM 3.1, just another part of DICOM Since DICOM 3.1, just another part of DICOM

DICOM RT Objects

RT Image

Conical Imaging Geometry Conical Imaging Geometry

Conventional Simulators Conventional Simulators Virtual Simulators ( Virtual Simulators (DRRsDRRs)) Portal Images Portal Images

RT Series Module

(8)

RT Dose

Radiotherapy Dose Radiotherapy Dose Distributions Distributions 2

2--and 3and 3--D Dose GridsD Dose Grids

Named or Unnamed Named or Unnamed Dose Points Dose Points Isodose Curves Isodose Curves Dose

Dose--Volume HistogramsVolume Histograms

RT Structure Set

Defines Radiotherapy Defines Radiotherapy- -Related Structures Related Structures Anatomical outlines, Anatomical outlines,

target volumes, critical

structures

Isodose lines, reference

point doses point doses May reference CT or MR May reference CT or MR images images

RT Treatment Record

Delivery Record Delivery Record Defines Three New Defines Three New IODs IODs:: RT Beams Treatment RT Beams Treatment Record Record RT Brachytherapy RT Brachytherapy Treatment Record Treatment Record RT Treatment RT Treatment Summary Record Summary Record

RT Plan

Contains Modules for Contains Modules for

Prescription Prescription Patient Setup Patient Setup Fractionation Fractionation

External Beam Treatment

Brachytherapy Treatment

(9)

RT

Beams

Module

Beam Beam Name Radiation Type

Beam Limiting Device (MLC, Collim.) Wedge Compensator Bolus Block Applicator # of Control Points Control Point Beam Energy

Gantry Angle, Rotation Direction Collimator Settings

MLC Positions Control Point

Control Point Sequence

Flexible Enough to Handle:

Static Beams, including static MLC Static Beams, including static MLC Arcs

Arcs

Dynamic MLC Dynamic MLC

Uses

Uses “

“Cumulative

Cumulative Meterset

Meterset

Weight”

Weight

”

concept

Portion of the beam delivered in segment Portion of the beam delivered in segment

Control Point Sequence

Control Point 0;

Cumulative

Cumulative MetersetMetersetWeight = 0Weight = 0 Defines all initial parameters Defines all initial parameters

Gantry, table, collimator/MLC settings, etc.

Subsequent Control Points

Cumulative

Cumulative MetersetMetersetWeight > 0Weight > 0 Specify all parameters which change Specify all parameters which change

Control Point Sequence

Static Beam

Control Point 0: Control Point 0:

Cumulative

Cumulative MetersetMetersetWeight = 0 Weight = 0

Define Gantry, Table, Collimator, MLC, etc

Define Gantry, Table, Collimator, MLC, etc…… Control Point 1:

Control Point 1:

Cumulative

Cumulative MetersetMetersetWeight = 1Weight = 1

(No other parameters defined)

(10)

Control Point Sequence

Arc Beam

Cumulative

Cumulative MetersetMetersetWeight = 0 Weight = 0

Gantry Angle =

Gantry Angle = _i_i

Gantry Rotation Direction =

Gantry Rotation Direction = CW/CCWCW/CCW

All other Parameters (collimator, table,

All other Parameters (collimator, table, ……))

Cumulative

Gantry Angle =

Gantry Angle = _f_f

Gantry Rotation Direction =

Gantry Rotation Direction = NONENONE

Control Point Sequence

Dynamic MLC,

N

Segments

Cumulative

Initial MLC Leaf Sequence

S

00

All other parameters

All other parameters Control Point 1: Control Point 1:

Cumulative

Cumulative MetersetMetersetWeight = 1/NWeight = 1/N

MLC Leaf Sequence

S

11

Control Point Sequence

Dynamic MLC,

N

Segments (continued)

Control Point r: Control Point r:

Cumulative

Cumulative MetersetMetersetWeight = r/NWeight = r/N

MLC Leaf Sequence MLC Leaf Sequence

S

rr … … Control Point N: Control Point N: Cumulative

MLC Leaf Sequence

S

NN

X Y Z

DICOM RT Coordinate System

IEC 1217 IEC 1217 Right Right--handedhanded Positive rotations CW Positive rotations CW looking along + looking along +veveaxisaxis Zero angle is nominal Zero angle is nominal (

(unrotatedunrotated) position ) position Defines Series of Defines Series of Coordinate Systems: Coordinate Systems:

Fixed, Gantry, Collimator,

Wedge, Table,

(11)

Z_f

Coordinate Systems

Fixed System Fixed System Origin at Isocenter Origin at Isocenter Z

Z--axis verticalaxis vertical Y

Y--axis coaxis co--linear with linear with

rotation axis of

gantry

X

X--axis at right angles axis at right angles

to Y, Z to Y, Z Yf Xf I S X_g Yf,Yg Zg Zf Xf g Ig, Io

Gantry Coordinate System

Stationary w.r.t. Stationary w.r.t. Gantry. Gantry. ZZ_g_g--axis axis passes thro radiation passes thro radiation source S

source S

Derived from Fixed Derived from Fixed Coordinate System Coordinate System by rotation about Y by rotation about Y- -axis axis S Yb

Beam Limiting Device

Coordinate System

Zb X_b S, Ib Io b Radiation Field

Collimator Rotations

(Viewed from radiation source) X1 X2 Y1 Y2 Xb Yb FY Fx Yg X_g b

(12)

MLC

-

X Positions

Yb Xb X1,1 X1,2 X1,n X2,n X2,2 X2,1

Leaf Positions are

mechanical

boundaries projected

onto Isocenter plane

Positions sent in Positions sent in order order X X1,11,1,X,X1,21,2,,……XX1,N1,N,, X X2,12,1,X,X2,22,2,,……XX2,N2,N

MLC

-

Y Positions

Yb Xb Y1,1 Y1,2 Y1,n Y2,n Y2,2 Y2,1

Leaf Positions sent

in order in order Y Y1,11,1,Y,Y1,21,2,,……YY1,N1,N,, Y Y2,1_2,1, Y, Y2,22,2,,……YY2,N2,N

DICOM 3 Parts

10. Media Storage and File Format

11. Media Storage Application Profiles

12. Physical Media Formats

13. (Retired)

14. Grayscale Display Standard

15. Security

16. Content Mapping 1. Introduction and Overview

2. Conformance 3. Information Object

Definitions

4. Service Class Specifications 5. Data Structures & Semantics 6. Data Dictionary 7. Message Exchange 8. Network Communication Support 9. (Retired) http://medical.nema.org/dicom/2003.html

Conformance

DICOM Part 2 specifies the structure of a

conformance statement

DICOM does not specify a test suite or a

compliance verification mechanism

All DICOM implementations must be supported

by a properly constructed conformance

statement

(13)

DICOM Conformance Statement

Implementation Model which describes the Application Implementation Model which describes the Application Entities in the implementation

Entities in the implementation

Detailed specification of each Application Entity Detailed specification of each Application Entity

SOP Classes supported

policies for initiation and acceptance of associations

policies for initiation and acceptance of associations Presentation Contexts

Presentation Contexts SOP options SOP options

Supported communications protocols Supported communications protocols Specializations Specializations Configuration Configuration