The Electronic Healthcare Enterprise: A Primer on PACS

& Integrated Workflow

DICOM Basics All I Really Need to Know!

January 2003

DICOM Basics

Finding your way through the DICOM Maze . . .

DICOM Basics DICOM Myths

There is a DICOM Genie that will cure all my problems!

DICOMGenieTrust

ME!

DICOM Basics

What is DICOM? Acronym for . . .

Diagnostic Imaging and COmmunications inMedicine

A standard for data exchangeA common information model

Patient

Study

Series

Image

has

contains

contains

NameMRNAge

DICOM Basics

DICOM AnalogyMaking a phone call

Use your new Digital/1X enabled cellular phone to call for your messages.

The call does not go through . . .

What is the problem?The area you are in does not support Digital enabled phones - only analogue phones!

Example of a low-level communication failure.

DICOM BasicsYou get to a land line and make the call . . .

Your message says to call Antonio Correlli in Italy requesting you to speak at his conference.

You call Antonio’s office and the person who answers does not speak your language nor do you speak their language.

It is now established the hardware works (compatible), BUT, languages do not match and so still no communications.

DICOM Basics

Fortunately, Antonio’s cousin happens to be in the office and does speak English - so you are suddenly able to communicate.

In preparation of your trip you ask what temperature it is in Italy so you can pack appropriately. The cousin says it is 37 degrees at this time of year. The plan is to pack warm clothes.

You arrive 10 days later in Italy and it is very hot!

DICOM Basics

Antonio’s cousin told you the temperature he is most familiar with; 37 degrees – Celsius.

Your assumption was Fahrenheit.

What is the problem?

Differentiation of units between communications.

DICOM Basics

You informed Antonio’s office of your need for two beds in your room. They reply it will not be a problem.You arrive at your room with your wife and two children. The room has two single beds.What is the problem?They thought you were bringing a co-worker and did not understand your need to bring your spouse and children.

DICOM Basics

Technology Communications Requires Compatibility in . . .

Hardware – compatible phone systemsProtocols – common languagesDefinitions – units of temperatureModels – definition of a room with two beds

DICOM Basics

DICOM addresses image communications needs

What information do you want to communicate?

What do you want to do with that information?

DICOM Basics

DICOM example courtesy of

Steven C. Horii, M.D., F.A.C.R.Department of Radiology

University of Pennsylvania Medical Center

DICOM Basics

Why DICOM?

OPEN SYSTEMS

To achieve a higher level of communication, leading to increased efficiency and better workflow

Enables technology to work for the user

To facilitate connectivity and interoperability of medical imaging equipment

DICOM Basics

Who uses DICOM?Modality Providers, PACS Component Providers, Interface Engines

Who talks DICOM?Modalities, PACS, HIS & RIS via PACS Gateway/Broker and brokerless

Is there a DICOM Version 4.0 on its way?No, the standard is constantly evolving – changes every two months – DICOM has removed the 3.0 version in favour of the acronym of DICOM

DICOM BasicsDICOM is Not:

The answer to all your networking problems

A networking architecture nor dependent on network architecture

Available for all older modalities

A static standard – never more than 2 month old

Easy to understand

Does NOT Guarantee Interoperability

Does NOT cover every operation of PACS such as image deletion, migration or pre-fetching

DICOM Basics

DICOM is . . .Based on conformance with the Open System Interconnect (OSI) reference model

OSI defines a 7-layer protocol stack

DICOM is an “application-level” standard, which means it exists inside layer 7 (the uppermost layer)

DICOM BasicsDICOM provides:

Standardized formats for imagesA common information modelApplication services Services for communication across a network and on removable mediaVoluntary Conformance Statements – does not confirm interoperability between different devicesProtocols for communication

• Point to Point Communication• Not a Broadcast Communication like HL-7

DICOM BasicsDICOM Standard Sections

Part 1 Introduction & OverviewPart 2 ConformancePart 3 Information Object DefinitionsPart 4 Service Class SpecificationsPart 5 Data Structures & SemanticsPart 6 Data DictionaryPart 7 Message ExchangePart 8 Network Communications Support for

Message ExchangePart 9 Point-to-Point Support Communications

Support for Message ExchangePart 10 Media Storage and File Format for Media

Exchange

DICOM BasicsDICOM Standard Sections

Part 11 Media Storage Application ProfilesPart 12 Media Formats & Physical Media for

Media InterchangePart 13 Print Management Point-to-Point

Communications SupportPart 14 Grayscale Standard Display Function

Part 15 Security Profiles

DICOM Basics

DICOM Engineer DICOM

Engineer

and work on the standard some more!!!

DICOM Basics

All I technically really need to know . . .

DICOM Basics

To successfully use DICOM in a multi-vendor environment there needs to be a correct matching of services and roles.

How is this achieved?

DICOM BasicsDICOM Service Classes are divided into multiple functional areas. The most relevant Service Classes apply to the following functions:

StorageQuery and Retrieve (Q/R)PrintSecondary CaptureModality Worklist ManagementModality Performed Procedure StepStorage CommitmentPrinter ConfigurationInterchange Media Storage

DICOM BasicsDICOM Service Class Principles

Each Service Class is divided into Users and Providers

Users – use the service of another device

• Service Class Users - SCUProviders – provide the service for users

• Service Class Providers - SCP

DICOM BasicsDICOM Service Classes

DICOM Service Class Users (SCU)DICOM Service Class Providers (SCP)

DICOM Service Class User – Uses a service of another device

Example – DICOM Workstation uses the service of a DICOM printer to print images

DICOM Service Class Provider – Provides a service to another device

Example – DICOM Archive provides the service of storing patient exams sent from MRI

DICOM BasicsDICOM Storage

Most common Service ClassEnables the exchange of images and other DICOM Objects between devicesConsists of a DICOM Header containing patient demographics, specific attributes and instructions related to the image that is contained within that DICOM file from that specific modality – Plus –the image data that comprises that digital imageNative DICOM interface facilitates complete image manipulation and post image processing

DICOM BasicsDiagnostic

Workstation

DICOM Storage SCUDICOM Storage SCP

DICOM Storage

DICOM Basics

DICOM Query/RetrieveFacilitates the query of databases or other devices for informationFacilitates the retrieval of a copy of the objects such as images from the current residence to a new desired locationExample:• Query a MR for a specific patient and retrieve the

patient’s exam from the MR to the Diagnostic Workstation

DICOM Basics

DiagnosticWorkstation

DICOM Query SCU

DICOM Query SCP

DICOM Query/Retrieve

DICOM BasicsDICOM Print Management

Facilitates the print of DICOM files/images from any print location to any DICOM printer located on the networkTransfers the instructions to print along with the data to printExample:• The Diagnostic Workstations sends 12 images

from a MR exam composed in a specific order to the DICOM laser printer

DICOM Basics

Laser Printer

DiagnosticWorkstation

DICOM Print SCU

DICOM Print SCP

DICOM Print SCU

DICOM Print

DICOM BasicsDICOM Secondary Capture

Facilitates the capture of images from non-DICOM legacy modality using either frame-grabber technology or digital stream to compose a DICOM image fileDoes not acquire all the specific image attributes and instructions – therefore offers limited image manipulation and no post-processing abilitiesExample:• Film digitizer acquires film-based images • DICOM Interface Black Box enables legacy Ultrasound

unit to share images using DICOM format with limited functionality

DICOM Basics

DICOM SecondaryCapture Diagnostic

Workstation

DICOM Print SCU

DICOM SecondaryCapture SCP

DICOM BasicsConversion of legacy systems to DICOM

“Legacy” Systems – “existing equipment that will not be replaced for a period of time”Examples – Ultrasound, CT, Angio, R/F

Two methods for conversionOEM software upgrade – “Native” DICOM

• Modality provides a digital output of image data with all appropriate DICOM header fields populated

DICOM Black Box – vendors Merge, Dejarnette, Kodak, etc.

• Frame Grabbers – 8 bit – Does a video frame grab to digitize the image

• DICOM Secondary Capture – 12 bit – does not populate all appropriate DICOM header fields for image manipulation – I.E. Window/leveling

DICOM Basics

DICOMConversion

Box

DICOMSecondary

CaptureSCU

Legacy Radiography/Fluorography

DICOM Secondary Capture

DICOM BasicsModality Worklist Management

Facilitates the transfer of patient demographic information between the RIS and a modalityEliminates the need to re-key dataEliminates human error during re-entry of data – ensures data integrityExample:• Patient data is transferred from RIS through PACS

Gateway/Broker to MRI unit

DICOM Basics

RIS

PACS Gateway/Broker

HL- 7Patient Demographics

DICOM ModalityWorklist Management

Broker Environment

DICOM Basics

Modality Archive

RIS

HL - 7 PatientDemographics

DICOM ModalityWorklist Management

Broker-less Environment

DICOM BasicsStorage Commitment

Facilitates a device to request another device to accept storage responsibility for images forwardedFacilitates the modality to delete local images once the archive has committed to store imagesExample:• MR forwards a storage commitment message to

the archive to confirm the storage of Mary Smith’s MRI exam

DICOM Basics

Modality Archive

DICOMStorage Commitment

DICOM Storage Commitment

DICOM BasicsModality Performed Procedure Step

Informs other devices (RIS and PACS) when specific patient exams are started, current status, and complete (aborted)Messages how many series, and images in each series in each exam, consumables, radiation dose delivered, etc.Example:• MRI sends MPPS message to RIS indicating Mary Smith

MR head exam is complete to trigger scheduling and billing

• MRI sends MPPS message to PACS Archive indicating that there were 3 series – Series 1 contain 112 images, Series II contain 78 images, etc. to ensure the archive has received all images and can store all images.

DICOM BasicsDICOM Performed

Procedure Step

Modality Archive

RIS

DICOM PerformedProcedure Step

Triggers Schedule Update &Billing Information

Triggers the addition of theexam to a reporting Worklist -confirms images for storage

DICOM PerformedProcedure Step

PACS Gateway/Broker

DICOM BasicsInterchange Media StorageDefines the formats for file storage; compression; what images are written to media“Basic Cardiac Angiography” is most commonly accepted/ implemented

ISO 9660 CD-RLossless JPEG compression512 matrix 8- bit multi-frame cardiac X-Ray Angiography

Additional DICOM specified profiles:General purpose exchange of any uncompressed images on CD-RBasic and 1K Angiography images compressed with lossless JPEG on CD-RCT & MRI images compressed with lossless JPEG on CD-R and 130 mm MODUltrasound Images uncompressed or compressed on CD-R, 90 mm and 130 mm MOD

Additional profiles will be added to the standard as applications and media change

DICOM Basics

CD Burner

Hospital A

Clinic B

Referring PhysicianOffice

DICOMInterchange Media

DICOM BasicsImage Object Definitions – (IOD)

IOD’s describe the data structures that contain image data and information• Example: CT is 12 bit grayscale vs. Ultrasound

is 24 bit colourTwo key IOD sub-classes –• Single Frame Images and Multi-Frame Images

Affect two key PACS components – Archive and Image Display applicationsRFP Requirement – all current and future applications for PACS

DICOM BasicsSingle Frame Images- Currently Available

Secondary Capture (SC) Scanned FilmsComputed Radiography (CR)Digital X-Ray (DR)Computed Tomography (CT)Magnetic Resonance (MR)Ultrasound (US) Nuclear Medicine (NM)Radiotherapy (RT) Image, Dose, Plan, Structure Set, RecordHardcopy Image (HC)Grayscale Softcopy Presentation State Store (PR)Positron Emission Tomography (PET)

DICOM Basics

Multi-Frame Images – Currently AvailableUltrasound (US)Nuclear Medicine (NM)X-Ray Angiography (XA)X-Ray Fluoroscopy (XRF)

DICOM Basics

Additional IOD’s Identified –Intra-oral Radiography (IO)Hardcopy Image (HC)Visible Light (VL) Endoscopy, Microscopy, PhotographyWaveforms (WV), Including ECG, Hemodynamic and Audio – Time based waveformsStructured Reporting (SR)

DICOM BasicsExample:

MRI sends an exam to the PACS archiveDICOM Storage SCU

Archive receives the exam and stores it DICOM Storage SCP

Archive sends the exam to the Diagnostic Workstation

DICOM Storage SCP

Diagnostic Workstation displays the exam to be interpreted

DICOM Storage SCU

DICOM SecondaryCapture

Patient DemographicsHL - 7

DICOM Modality Worklist Management

DICOM Storage

PACS Gateway/Broker

DICOMConversion

Box

RIS

PACS Archive

DiagnosticWorkstation

ReferringPhysicians

Verification

DICOMSecondary

Capture DICOM Storage

DICOM Query

DICOMRetrieve

DICOMPrint

Questions