Intro to DICOM

Course Name Module #: Lesson # Title Page 1Toshiba America International Training Academy

2003, Toshiba America Medical Systems, All rights reserved.

Introduction to DICOM

• Introduction• The DICOM Interface• History• Information Objects• Roles• Service Classes• Conformance• Parts of the Standard• Other DICOM Terms

Traditional imaging workflowTraditional imaging workflow

ClinicalClinicalInterpretationInterpretation

ImageImageAcquisitionAcquisition

Result DistributionResult Distributionto to

Referring PhysicianReferring PhysicianImage OutputImage Output

on Filmon Film

FilmFilmManagementManagement

andandLibraryLibrary



Introduction-Evolving from a hospital need

In the 1980’s, it became clearthat the tremendous growthin image acquisition systems, display workstations, archivingsystems and Hospital Infor-mation Systems made it vital to have a good connectivity and interoperability between allkinds of (medical) equipment.

There was a strong need to:• Share diagnostic information in different departments• Combine all medical information on a patient for better diagnostic results• Complete the patient folder with results from all medical studies performed



Why do we need a (DICOM) standard ?

Without a standard, custom interfaces are needed for each imaging device.

Currently, in a typical multi-vendor imaging department, there is little compatibility of equipment, so custom interfaces are developed or purchased in order to interconnect the equipment.

When Dicom is built into a medical imaging device, it can be directly connected to other equipment via a standard network.

CTCTWithout a standard:

PrintPrint

Custom Interface



The hospital benefits of the Dicom standard

The benefits are:• enables the hospital to select the best equipment per diagnostic application• improves the level of interactive communication among medical professionals• provides a wider access to images and associated information• creates new opportunities for handling diagnostic images in more cost effective ways.

• Increase diagnostic quality• Cost effective



DICOM – The Standard in communicating medicine

DICOM is the industry standardfor transferal of medical images, patient demographics and related information.

DICOM enables digital communication between diagnostic equipment, printers, picture archives etc. from various manufacturers (vendors)

DICOM is the firstmulti-modality standard( US, CT, MRI etc. )

• Multi-modality standard• Multi-vendor standard



Introduction - What DICOM stands for

In order to simplify and improve equipment connectivity,medical professionals joined forces with manufacturers in aninternational effort to developDICOM.

DICOM stands for: D = DigitalI = Imaging andCO = Communications inM = Medicine



History

DICOM is the result of an alliance of potential users of the standard ( Members of the American College of Radiology - ACR ) with the companies that manufacture medical equipment ( Members of the National Electrical Manufacturers Association -NEMA ) that began in 1984.

DICOM has also been embraced by other worldwide standards organizations and other healthcare disciplines outside of radiology.

ACR(Users)

NEMA(Manufacturers)

DICOMstandard



History

Through development over the course of more than the past decade, DICOM continues to grow and evolve to meet the needs of the imaging community. •ACR/NEMA 1.0 (Ó1985)•ACR/NEMA 2.0 (Ó1988)•DICOM 3.0 (1993) current evolving standard

Work continues on many useful supplements to DICOM which extends its usefulness to other medical disciplines, such as Endoscopy, Radiation Therapy Planning, Pathology and Diagnostic Reporting

DICOM3.0

DICOM3.0

DICOM

199519951996199619971997199819981999199920002000

More than 40 supplements during the past years

DICOM, the expanding standard



Image transfer via networks

Image AcquisitionImage Acquisition DICOM uses computer industry standards to provide a network connection with other devices. This allows easy connection of DICOM imaging equipment to existing hospital networks.

Intra-hospital connections, communication with remote clinics and tele-radiology applications are supported.

CTCT

ArchiveArchive

Standard hospital networkStandard hospital network

DistributionDistribution

PrinterPrinter



The DICOM interface

A manufacturer uses the standard to design and build a product. The Dicom standard describes all of the detailed functional specifications which a device with a communication-interface (allowing one computer to ‘talk’ to another computer) must employ to meet the standard.The standard provides a common reference for all developers of medical equipment.

The interface uses a set of computer software which executes the DICOM protocol.The software also formats the data for transmission.

Image AcquisitionImage Acquisition

DICOM Interface

Inside medical equipment

e.g. Ultrasounde.g. Ultrasound

DICOM image



DICOM concepts

Information Objects:Information Objects standardize

the content of a wide range of image types (e.g. CT, MRI, NM, US, Xray)

Service Classes:Service classes define what to do

with those Objects (e.g. store, move, print) across the network.

Role Definition:In the Role Definition is defined

which equipment is the transmitter of information and which equipment is the receiver of information.

DICOMconcept

Information Objects

RoleDefinition

ServiceClasses

Three concepts specified



Information Objects

The Information Objects consist of two parts:•Object Attributes•Image Object

Object Attributes:This is the so called header information of an image containing Patient information, modality information etc.

Image Object:The Image Object contains the pixel data of the medical image, like the pixel data of a CT-image.

Information Objects

Patient module : Name, birthday, sex etc• Study module : Study date, time, ID etc• Series module : Modality, series etc• Image plan module : Slice orientation, slice thickness• Etc.

Image Objecte.g. CT pixel matrix

Object Attributes•patient information•acquisition parameters•modality etc

Example: CT Object

Attributes

Image



Information Objects

• Information Objects are not only images and graphics but also studies, reports, lists, etc.

• An information Object has:– Modules– Attributes



Data elements

In all the modules there are standard data elementsthat can be :M : Mandatory.C : Conditional.U : User options.M* : Mandatory with special conditions.U* : User option with special conditions.

All the defined data elements start with an even number (like in ACR-NEMA).

Private data elements have an odd number and may contain data that is not defined in the standard data elements.

example :Relative Couch position : 0019 110B



Service Classes

A Service Class defines the service or operation that can take place ( e.g. printing, storing etc.) now that the objects have been defined.

Storage Service Class

Query and Retrieve Service Class

Print Service Class

Modality Work list Management Service Class

Modality Performed Procedure Step Service Class

Media Storage Service Class

Storage Commitment Service Class

Structured Reporting Service Class



Roles –storage class user, provider

To setup communication, two roles have to be specified:

Service Class User•The device that sends information or an image on the network is a Service Class User ( SCU ).The SCU uses the network service. ( e.g. A CT scanner uses a network-workstation to display the CT images)

Service Class Provider•The device that receives information or an image from the network is a Service Class Provider ( SCP ).The SCP provides the service to the network ( e.g. a network-archive provides the archiving service )

ArchiveArchiveImageImageacquisitionacquisition

Service Class ProviderService Class Provider(SCP)(SCP)

Network

I am Providing the Archive Services

I am a User of the Archive Services

Service Class UserService Class User(SCU)(SCU)



Roles –Print class user provider

A CT scanner uses the Print Services of a printer which is connected to the network.

A Printer provides the Print Services to the network

A SCU always needs a SCP and visa versa.

PrinterPrinterImageImageacquisitionacquisition

Service Class ProviderService Class Provider(SCP)(SCP)

Network

I am Providing the Print Services

I am a User of the Print Services

Service Class UserService Class User(SCU)(SCU)



If two devices want to have a successful communication, we must consider the following:

• What functionality is supported?• Communication Rules.

ServiceClasses

Information Objects

RoleDefinition

The DICOM functionality is defined as follows:Functionality =

+ +

E.g. : XRAY image + SCU + Storage

To make a successful communication between Systemswe must consider the following communication Rules:

• They must support identical Information Objects• They must support identical Service Classes• A SCU needs a SCP ( a User needs a Provider )

Communication examples are:CT Storage SCU and CT Storage SCP : OKXRAY Print SCU and US Print SCP : No good

Successful communication



Association request

If two devices want to have a successful communication, they first must negotiate supported functions and rules.

This is accomplished by an association request or “handshake.”


Storage ServiceStorage ServiceClass ProviderClass Provider

Network

2. Yes, I can STORE US images in my archive

2

1. I need to STORE US images, do you support this?

Storage ServiceStorage ServiceClass UserClass User

1



Verification Service classesThe verification Class is used to test

DICOM connections over the network. It uses the DICOM echo command to another DICOM compatible workstation to verify the connection.

Most systems have the verification class user and provider function to be able to test connections.

Provider means that when you receive a DICOM echo command that you will respond to this (you provide this service to the users on the network).

User means that you can send a DICOM echo command to another system. (you use the service from a provider on the network).

Verification (SCU)Verification (SCU) Verification (SCP)Verification (SCP)

EchoEchoSCPSCPSCUSCU



Storage Service Class

•The storage class describes the storage of digital images in via a network.

•In the Storage Service Classes, two Roles can be defined: User and Provider

•If you are Storage Class User, it means that you can send data to a Storage Class Provider.

•If you are Storage Class Provider, it means that you can receive data from a Storage Class User, provided that both systems do support the same Image-object. E.g. an US-image object.


Storage ServiceStorage ServiceClass ProviderClass Provider

Network

I can store US-imagesin my archive

I can send US-imagesto a Storage device

Storage ServiceStorage ServiceClass UserClass User



Query and Retrieve Service Class

•The Query and Retrieve Service Class supports basic operations to access and move images based on search criteria, such as retrieving an image of a particular study of a patient X

•If you are Query and Retrieve Useryou can ask for a list from a Query and Retrieve provider on the network and pull any desired image from this provider to your local system.

•An additional condition is that both systems support the same DICOM Image Object ( e.g. US-Object )

•If you are Query-and-retrieve-Provider you accept a request for a list from a Query-and-retrieve-User over the network and send the desired data images to this user.

Archive server

QueryQuery

2. Here you have the list

3. Please send meimages no. 4

4. Here youhave image

no. 4

1. Please send me a list of studies of

patient X

Viewing station



Modality Worklist Management Service Class

PatientPatientschedule listschedule list

New patientNew patient

The worklist management service class is intended to transfer patient information between the hospital server (HIS=Hospital Information System, RIS=Radiology Information System) and the imaging equipment.

All clinical appointments in a hospital are normally made on a central HIS/RIS server. WithWorklist management class it is possible to send the patient information from the central desk to all imaging equipment. The advantage is that the operator at the Ultrasound system doesn't need to type in all the patient information (with the risks of typing mistakes). Even a bigger advantage is that traceability of patient images in the archive can be better guaranteed.

HIS/RIS-Server

Provider

TOSHIBAUser



DICOM Data Exchange Walkthrough

TCP

IP

Ethernet card Ethernet card

Application

TransferCommunicationProtocol

Network(Internet Protocol)

Link

SCUSCUSCPSCP

DICOM

TCP

IP

DICOM

ImageImage

(DICOM I/F PWB)(DICOM I/F PWB)

DICOMDICOMProtocolProtocol

TCPTCPProtocolProtocol

IPIPProtocolProtocol

EthernetEthernetProtocolProtocol

NetworkNetwork



Data transfer

• When the system starts the communication, it will send a package to the other system (provider) with– The other party's IP address– The other party's Port Number.– The other party's AE title (Application Entity)– The systems IP address for return handshake

• In the other system this packet will be passed upwards and because of the port number, the TCP layer knows to which application this package must be passed. The DICOM provider will now check the AE Title and respond to the source IP number with the source port number.

• The packages that are sent are called datagrams.



OSI model• Application• Presentation• Session• Transport• Network• Datalink• Physical

• Application• Presentation• Session• Transport• Network• Datalink• Physical• Application



Image transfer via networks

• OSI model

DICOM Application Entity

Ethernet, ATM, FDDI, ISDN, etc.

OSI AssocationaControl (ACSE)

OSI PresentationOSI Session

OSI TransportOSI Network

OSI LLC

DICOMUpper Layerprotocol for

TCP/IPTCP

IP

DICOM "Added Value"

OSI Upper LayerService Boundary

StandardNetworking



DICOM Terminology • Application Entity• Image Object Definition• Service Class• Association• DIMSE Services

Application EntityThe label or name of a DICOM application

Image Object Definition (IOD)The standardized format for data based on the modality of the image. CT images have a different IOD than do US images.



DICOM Terminology • Application Entity• Image Object Definition• Service Class• Association• DIMSE Services

Service Classassociates one or more Information Objects with one or more Commands to be performed upon these objects. Service Class Specifications state requirements for Command Elements and how resulting Commands are applied to Information Objects. Service Class Specifications state requirements for both Users (SCU’s) and Providers (SCP’s) of communications services.



DICOM Terminology

AssociationThe initial ‘handshake’ between Application Entities (AE’s) that represents an agreement the SCP will support the requested services of an SCU.

DIMSE ServiceGeneric services which act upon instances of an information object. The specific messages that AE’s use to

• Application Entity• Image Object Definition• Service Class• Association• DIMSE Services



DICOM data format

• Since there are 2 different data formats commonly used you must specify what format you use in your DICOM conformance statement:– Little Endian: If byte order 68A4 is

received it will be converted to A468.

– Big Endian: If byte order 68A4 is received it is not converted.

Most DICOM programs accept both forms and convert it automatically to their desired format (depending on the CPU and Operating System.

The default setting is LittleEndian.



Conformance Statement

Anyone claiming that their equipment or software conforms to the DICOM standard, must be able to provide a so called Conformance Statement that describes exactly how that device or software conforms to the standard.

A question that is frequently asked about the DICOM standard is :If DICOM is a standard, why is a Conformance Statement required?Isn’t it sufficient to simply state that equipment conforms?As has already been explained, DICOM can support many different Information Objects, Service Classes etc. Because of the wide multi-modality scope of the DICOM standard, a full implementation of the DICOM standard is seldom targeted in a medical product development plan.

DICOM StandardDICOM Standard

System ASystem A

System BSystem BConnectivityConnectivity



Conformance Statement

The Conformance Statement of a DICOM interface (defining a part of the DICOM standard), contains the following items:•Which Information Objects are supported•Which Service Classes are supported•Which role ( SCU or SCP ) is supported

A user or manufacturer trying to determine if two DICOM devices will communicate to suit a particular application, can compare the conformance statements side by side.

This process does not guarantee that the two devices will communicate properly, but obvious problems, such as one device not supporting the service needed by the other, can be caught.

TOSHIBA No.2A260-669E

DICOMCONFORMANCE STATEMENT

FORTOSHIBA WHOLE BODY X-RAY CT SCANNER

X-SERIES

Example of a Toshiba Conformance Statement:



Toshiba Conformance Statements

• Most are available from TAMS Web Site at http://www.toshiba.com/tams



The Standard

Introduction and Overview• Overview of the DICOM

standard. It describes the history, scope, goals, and structure of the standard.

Conformance• Defines principles that

implementations claiming conformance to it are required to follow.

• Defines DICOM Conformance Statement, minimum general conformance requirements, etc.

Grayscale standard display functionsPart 14

Print managementPart 13

Media formats and physical mediaPart 12

Media storage application profilesPart 11

Media storage and file formatPart 10

Network communication support for message exchange (50 pin)Part 9

Network Communications Support for message exchange (TCP/IP)

Part 8

Message exchange (DIMSE)Part 7

Data dictionaryPart 6

Data Structure and EncodingPart 5

Service Class SpecificationsPart 4

Information Objects DefinitionPart 3

ConformancePart 2

Introduction and OverviewPart 1

Section



The Standard

Information Object Definitions• Specifies all the Information

Object Definitions (i.e. images, overlays, print objects, etc.)

Service Class Specifications• Defines all the Services Class

and more important SOP classes (i.e. Store, Query, Retrieve, Print, etc.)

Data Structure and Encoding• Defines the structure and

encoding rules of the Data Set (encoding, transfer syntax, etc.)








Part 8






ConformancePart 2


Section



The Standard

Data Dictionary• Registry of all DICOM data

elements and unique identifiers (UIDs).

Message Exchange• Defines the DICOM

Message Service Element (DIMSE). It specifies the protocol to send commands such as Store, Find, Move, Get, Create, Action, Event, Set, and Delete.

Network Communication Support for Message Exchange

• Defines the services and upper layer network protocols (i.e. association negotiation, support for TCP/IP, OSI, etc.)








Part 8






ConformancePart 2


Section



The Standard

Network Communication Support for Message Exchange

• Define the 50-pin protocol. This portion of the standard is no longer significant in an actual networking clinical environment.

Media Storage and File Format• Specifies the general model

for media interchange (i.e. DICOM File Format, Directory, etc.)






Network communication support for message exchange (50 pin)

Part 9


Part 8






ConformancePart 2


Section



The Standard

Media Storage Application Profiles

• Specifies a selection of choices which are applicable to a specific need or context in which media interchange is to be performed (i.e. X-ray Cardiovascular, etc.)

Media Formats and Physical Media

• Specifies a set of physical media and formats (i.e. CD-R, 3" MOD, etc and DOS, ISO 9660, etc.)

Print Management• Point-to-point

Communication Support• Defines a point-to-point

print protocol replacing the network.








Part 8






ConformancePart 2


Section



The Standard

Grayscale Standard Display Function

• Specifies the display standard used to obtain visual consistency in how a given digital image appears whether viewed on separate display monitors or light boxes.








Part 8






ConformancePart 2


Section



Questions

Intro to DICOM

Documents