Picture Archiving and Picture Archiving and Communications Systems (PACS) Communications Systems (PACS)

considerationsconsiderations

J. Anthony Seibert, Ph.D.J. Anthony Seibert, Ph.D.Professor of RadiologyProfessor of Radiology

University of California Davis Health SystemUniversity of California Davis Health SystemSacramento, CaliforniaSacramento, California

Digital Imaging Summit and Workshop for Digital Imaging Summit and Workshop for Veterinary RadiologistsVeterinary Radiologists

San Luis Obispo, CaliforniaSan Luis Obispo, CaliforniaMay 29May 29--31, 200831, 2008

DIGITAL IMAGING IN RADIOLOGYDIGITAL IMAGING IN RADIOLOGY

•• DigitalDigital imaging is an imaging is an essentialessential component of component of Electronic Imaging, Telemedicine and Electronic Imaging, Telemedicine and Remote DiagnosisRemote Diagnosis

•• Steps for digital imagingSteps for digital imaging–– AcquisitionAcquisition–– DisplayDisplay–– DiagnosisDiagnosis–– DistributionDistribution–– ArchiveArchive

•• Computed & Direct Radiography (CR / DR)Computed & Direct Radiography (CR / DR)•• Digital Subtraction Angiography (DSA)Digital Subtraction Angiography (DSA)•• Computed Tomography (CT)Computed Tomography (CT)•• Ultrasound (US)Ultrasound (US)•• Magnetic Resonance Imaging (MRI)Magnetic Resonance Imaging (MRI)•• Nuclear Medicine (NM)Nuclear Medicine (NM)•• Mammography & Breast ImagingMammography & Breast Imaging•• Cardiac, DEXA, Dental, OpticalCardiac, DEXA, Dental, Optical……. etc. etc.. etc. etc.

DIGITAL DIGITAL IMAGING MODALITIES IN IMAGING MODALITIES IN RADIOLOGY & MEDICINERADIOLOGY & MEDICINE

The “Big” Picture• “Digital” Radiology

MRIMRI

CTCT Nuclear MedicineNuclear Medicine UltrasoundUltrasound

Interventional AngioInterventional Angio

PACSPACS DigitalDigital RadiographyRadiography

Imaging volume

• Projection imaging 70%• Fluoroscopy 3%• Computed tomography 8%• MRI 6%• Ultrasound 10%• Nuclear Medicine 3%

Medical Imaging Modalities• Common thread

– Digital data (and lots of it!!)

• Problems– Proprietary structures– Unknown data format

• Solutions– DICOM and PACS– HL-7 and RIS– Networking and Informatics– IHE integration “profiles”

•• RIS (HIS)RIS (HIS)–– Radiology Information SystemRadiology Information System

•• Transcription, Reporting, Ordering, Scheduling, BillingTranscription, Reporting, Ordering, Scheduling, Billing

•• PACSPACS–– Picture Archiving and Communication SystemPicture Archiving and Communication System

•• Acquisition, Interpretation, StorageAcquisition, Interpretation, Storage

•• Integrated Medical ImagingIntegrated Medical Imaging–– RIS, PACSRIS, PACS–– Integrating the Healthcare Enterprise (IHE)Integrating the Healthcare Enterprise (IHE)

TerminologyTerminology

•• RISRIS--PACS IntegrationPACS Integration–– Data Synchronization, ValidationData Synchronization, Validation–– Interpretation & Results ReportingInterpretation & Results Reporting

•• New OpportunitiesNew Opportunities–– Value Added, PatientValue Added, Patient--less Examinationless Examination–– Computer Aided DiagnosisComputer Aided Diagnosis

•• Image Distribution (The Internet)Image Distribution (The Internet)–– Clinical Review, OR, Patients, ConferencesClinical Review, OR, Patients, Conferences–– Enterprise Integration Enterprise Integration -- EMREMR–– TeleradiologyTeleradiology

Integration and DistributionIntegration and Distribution

•• TCP/IPTCP/IP–– Standard Communications ProtocolStandard Communications Protocol–– The InternetThe Internet

•• HL7HL7–– Health Level 7Health Level 7–– RIS / HISRIS / HIS

•• DICOM 3.0DICOM 3.0–– Digital Imaging Digital Imaging COmmunicationsCOmmunications in Medicine v3.0in Medicine v3.0–– PACSPACS

•• HTTPHTTP–– HyperHyper--Text Transport ProtocolText Transport Protocol–– The World Wide WebThe World Wide Web

Communication ProtocolsCommunication Protocols

Infrastructure

• Platforms– Clients / workstations– Servers

• Physical Plant– Power– HVAC– Media

• Networking– Devices– Media– Topologies

• Storage– Hardware – software– Media– Topologies

Infrastructure Challenges

• Business– Cost vs. quality patient

care– Regulatory compliance– Access to data across

applications

• Clinical– Information when & where

needed– Loss or Corruption not

tolerated– Impact on patient care

• Technical– Lack of qualified technical

professionals– Management of increasing

amts of data– 100% data integrity &

availability– Security for data distribution

and storage– Standards vs. proprietary

solutions

Infrastructure issues

• Foundation of the digital healthcare enterprise• Highly available (>99.99%); each “9” $$$$• Documented and diagrammed• Made up of media and electronics• Data must be secure in flight & at rest• Proper planning is CRITICAL• Ongoing infrastructure support is CRITICAL

Image management issues

• Very large datasets impact storage & communications

• Very large annual volumes require data protection

• Variable image retention periods (patient age, exam type, etc.) requires lifecycle management

• Variable locations could have an impact on communications delays

A typical imaging solution

PACS Layout at UC DavisPACS Layout at UC Davis

MWLDICOM

iVau

lt

Modalities

Radiology ReadingiSite Radiology

Storage Mirror

Enterprise Image DistributioniSite Enterprise

Internet infrastructure

Customer Care

RIS

Off-SiteBackup

Real-time Monitoring

Emergency Backup Server

Exam OrdersHL7

100 BaseT to/from modalities1000 BaseT to database/server/archive

Workstation Hardware• Off the shelf hardware: 2 to 3 GHz CPU, multi-

core (dual or quad), Windows XP, 4 GB ram, PC3200 memory

• Video card with 512 MB, PCIe bus,10 bit output display, DICOM GSDF compatible

• Gigabit NIC

• 16x / 40x DVD / CD ROM

• 2 HDD, minimum 100 GB SATA, 3 GB/s, RAID

• Audio card for voice input

• Barcode reader, voice dictation system, etc.

Workstation Hardware• Two “classes”

– Primary (Radiologist) – Clinical (Remote and referring physician)

• Typical primary class workstation configuration– 2 high resolution / luminance LCD grayscale monitors

• >400 Cd/m2 luminance• 1536 x 2048 pixels (3 MP), 21 inch (52 cm)• Portrait mode

– 1 COLOR LCD “navigation” panel• 1600 x 1200 typical, 19 inch diagonal (47 cm)

Monitor – decision points

• Size and mode (21 inch portrait, monochrome)– Based on vertical chest radiograph

• Newer choices– 30 inch 4 MP, 6 MP, color LCD’s

• Color (will likely become the standard) – 3D volume visualization– Ultrasound– Nuclear Medicine– Functional MRI, other

Typical PACS workstation configuration

•1536x2048•10 bit •Grayscale•400 Cd/m2

NavigationMonitor1280x1024color

Basic Workstation Software Reqt’s

• Filters: sort studies by modality, location, time, etc.

• Worklist functionality: automate workflow

• Hanging protocols: arrange images and display

• Retrieving priors: pre-fetch or all spinning disk

• Graphic user interface: tool palette parameters

• Mechanical interface: keyboard, mouse, other

• User preferences: individual preferences for above

Archive• Slow, large archives on early generation PACS

• Migration to “all spinning disk” RAID (redundant array of independent disks) NAS (network attached storage) instantaneous access and “disaster recovery” digital tape backup

• Hierarchical storage management (HSM) is becoming less important with 3rd generation PACS

• “pre-fetching” and “auto-routing” are becoming less important

Spinning diskarchive modules

Server

DICOMProcessors &load balancingswitch

Databasestorage

UCDMC PACS

Current storage: 20+ TB of patient data stored and accessible on demand

DICOM: What the Physicist should know

• Where does DICOM come from?

• What does DICOM do?

• What do the terms mean?

• What parts of DICOM does a modality need to support or use?

• How does DICOM affect image quality?

Where does DICOM come from?

• American College of Radiology• National Electrical Manufacturers Association

(NEMA)• Established 1983, first published 1985• Followup standards in 1988 (ACR-NEMA 2.0)• 1993, DICOM 3.0 published and continuously

updated

What does DICOM do?• Addresses 5 areas of functionality

– Transmission and persistence of complete objects (images, waveforms, documents)

– Query & Retrieval of such objects– Performance of specific actions (e.g. film printing)– Workflow management (support of worklists)– Quality and consistency of image appearance

(both display and print)

• Network configurations– Application Entity (AE) title, IP address, TCP/IP port

number

DICOM Abbreviations

• AE title: Application Entity title

• DIMSE: DICOM message service element

• E-R: Entity Relationship

• IP address: TCPIP (internet protocol) address

• SOP: Service-object pair

• UID: Unique Identifier

• VR: Value Representation

What does DICOM do?• DICOM storage

– e.g., CT image storage SOP class, CR image storage SOP class

• DICOM print– Basic grayscale print management SOP class (SCU only)

• Query / Retrieve– Poll a DICOM device for a list of studies or patients, then retrieve

one or more

• Worklist Management– Download a list of “scheduled procedures” to the modality from

the RIS through a worklist management provider (PACS Broker)

• Modality Performed Procedure Step (MPPS)– Modality tells RIS that the procedure has been performed

What are DICOM objects?

• “Objects”– Information Object Definitions “IOD”

– Recipes of items to define an “instance” of a• CT/MR/CR/US/Digital X-ray (DX), digital mammo (MG) etc.• Basic film session (DICOM print)• Scheduled procedure for a worklist

– Attributes of the object are defined in modules• Patient module: Patient name, Patient ID• Study module: Study UID, Study Date, Accession Number • ……. And more…….

From DICOM Part 3: Information Object Definitions

Characteristics of moduleGroup number

Element number

Unique attribute identification Type 1 = mandatory, non-NULLType 2 = mandatory, NULL or emptyType 3 = optional

Group number even: “standard”odd: “private”

DICOM Attributes

• Attributes also have a defined “value representation”

Tag VR Value Length Value Field

Value Representation (DICOM part 5; explicit VR syntaxes)

Person name (PN) Last^First^Middle(Seibert^James^Anthony)

Date (DA) yyyymmdd(20060614)

Time (TM) hhmmss.frac(091545.87934)

What DICOM is needed for a modality?

• Store• Print• Modality Worklist• Performed Procedure Step• Presentation of Grouped Procedures• Archive Commit• Grayscale Standard Display Function (GSDF)• Grayscale Standard Presentation State (GSPS)

Conformance Statements

Conformance Statements

Don’t assume that desired functionality is available

Many capabilities are optional ….. $$

Bottom line:NegotiateTest and verifyWork with modality and

PACS vendors to achieve desired functionality

C-storeC-echoMWLQ/RPPSPrint………SOP classesPrivate tags

DICOM Metadata……

How does DICOM affect image quality?

• New PACS user: “When making measurements on DX images, values come out in pixels instead of millimeters. Why? ”

• DX IOD requires the DX detector module, which calls for “imager pixel spacing” in DICOM tag (0018,0064)

• CT IOD uses the image plane module with pixel spacing defined in tag (0028,1130)

• PACS workstation/viewer might not be looking for pixel spacing in the correct location

• PHYSICIST AS A TROUBLESHOOTER…….

PACS capabilities

• Hanging protocols• API – application program interface• 3rd party add-ons• Presentation State• VOI LUT• De-identification / anonymization (HIPAA)• Part 14 DICOM export• ……… and so on…..

Softcopy Grayscale Presentation State IOD

– Defines an object which can store or preserve the “state” of a referenced object (e.g., an image)

– Stores image orientation, window/level, measurements, annotations, masking shutters

– Radiologist making notes, adjusting window/level will produce a “presentation state” upon marking the study complete

OriginalOriginal

Radiologist Presentation StateRadiologist Presentation State

PACS remote access

• Security and firewall considerations• VPN: virtual private network

– Allows “tunneling” into the firewall– Produces a local IP address for a virtual presence

• Image compression– DTS….. Dynamic transfer syntax– JPEG2000….. Similar to DTS, adopted by DICOM

standard

• Access to UCDMC research PACS

IMAGE COMPRESSIONIMAGE COMPRESSION

•• 1 bit = a light switch, 1 bit = a light switch, ONON oror OFFOFF, 0 , 0 oror 1 1 (2 Values)(2 Values)

•• 1 byte = 8 bits 1 byte = 8 bits ‘‘00000000’’00000000’’ to to ‘‘11111111’’11111111’’ (256 Values)(256 Values)

•• 1 Kilobyte (KB) = 1,000 bytes1 Kilobyte (KB) = 1,000 bytes•• 1 Megabyte (MB) = 1,000 KB1 Megabyte (MB) = 1,000 KB•• 1 Gigabyte (GB) = 1,000 MB1 Gigabyte (GB) = 1,000 MB•• 1 Terabyte (TB) = 1,000 GB1 Terabyte (TB) = 1,000 GB•• 1 Pedibyte (PB) = 1,000 TB1 Pedibyte (PB) = 1,000 TB•• Average Radiology Exam is ~ 20MBAverage Radiology Exam is ~ 20MB

•• 280,000 Exams = ~ 280,000 Exams = ~ 5.6 Terabytes / year5.6 Terabytes / year @ UCDMC Radiology@ UCDMC Radiology

IMAGE COMPRESSIONIMAGE COMPRESSION

•• Average Radiology Exam is ~ 20MBAverage Radiology Exam is ~ 20MB

•• Lossless Compression Lossless Compression -- JPEGJPEG–– ~ 2:1 > 10MB ~ 2:1 > 10MB XferXfer

•• Lossy Compression Lossy Compression -- WaveletWavelet–– ~ 20:1 > 1MB ~ 20:1 > 1MB XferXfer

•• JPEG 2000JPEG 2000–– Combines Lossless techniques and Lossy WaveletCombines Lossless techniques and Lossy Wavelet–– Finally standards based Wavelet compressionFinally standards based Wavelet compression–– DICOM approval of advanced compression by 2000?DICOM approval of advanced compression by 2000?

IMAGE COMPRESSIONIMAGE COMPRESSION

OriginalOriginal500 Kbytes500 Kbytes

12:1 Wavelet12:1 Wavelet42 Kbytes42 Kbytes

Compression allows more efficient use of limited bandwidth (e.g., telephone modems)

IMAGE COMPRESSIONIMAGE COMPRESSION

OriginalOriginal8000 8000 KBytesKBytes

35:1 Wavelet35:1 Wavelet230 230 KBytesKBytes

IMAGE COMPRESSION: HOW MUCH?IMAGE COMPRESSION: HOW MUCH?

How much?

Original Wavelet, 10:1 20:1 40:1

~Visually Lossless ~Clinically Lossless Visible Blur

Courtesy of Nicholas Hangiandreou, Mayo Clinic, Rochester, MN

IMAGE DISTRIBUTION: Web and the Internet

IMAGE DISTRIBUTION: Web and the Internet

ImageArchive

(TB)

ImageArchive

(TB)

ControlSoftwareControl

Software

ReviewStation

ReviewStation

ReviewStation

ReviewStation

Web Servers

Web Servers

HospitalPCs

HospitalPCs

Radiology Departments

USUSCRCR

ClinicPCs

ClinicPCs

OfficePCs

OfficePCs

HomePCs

HomePCs

RadiologistsRemote

RadiologistsRemote

Radiologists

ImagingCenters

ImagingCenters CTCTMRIMRI

Courtesy of Dr. Keith Dreyer

PACS installation planning

• Location of server and major hardware• PC requirements for workstations,

environment and power considerations• “Mini-PACS” for ultrasound, nuclear medicine

– Color monitors– Application specific workstation requirements

• Reading room– Lighting– Furniture

Challenges

• Integration of different systems

• IHE: Integrating the Healthcare Enterprise– Addresses INTEROPERABILITY of systems– Provides INTEGRATION PROFILES and a

framework for performing needed functionality and workflow

– Scheduled Workflow, …..

• http://www.IHE.org

PACS quality control

• Interfaces• Redundancy and emergency backup• Software verification (distance accuracy

measurements, quantitative measurements)• MONITORS• Verification of correct data• Display and viewing conditions• Image compression & archiving• Disaster Recovery and backup plans

SUMMARYSUMMARY Enterprise distribution of images is crucial for implementation and application of technology

• Telemedicine and teleradiology allow the exchange of technological ideas and implementation in a diverse number of associated fields

• The Internet solves many problems, as recognized by the proliferation of web-based PACS and unified patient database (instead of Radiology centric orientation)

• New opportunities – Image acquisition and image processing tools– Imaging technology innovation for diagnosis and intervention