Picture Archiving andCommunications Systems (PACS) considerations Digital Imaging Summit and Workshop for Veterinary Radiologists San Luis Obispo, California May 29-31, 2008 J. Anthony Seibert, Ph.D. Professor of Radiology University of California Davis Health System Sacramento, California
DIGITAL IMAGING IN RADIOLOGY• Digital imaging is an essential component of Electronic Imaging, Telemedicine and Remote Diagnosis• Steps for digital imaging – Acquisition – Display – Diagnosis – Distribution – Archive
DIGITAL IMAGING MODALITIES IN RADIOLOGY & MEDICINE• Computed & Direct Radiography (CR / DR)• Digital Subtraction Angiography (DSA)• Computed Tomography (CT)• Ultrasound (US)• Magnetic Resonance Imaging (MRI)• Nuclear Medicine (NM)• Mammography & Breast Imaging• Cardiac, DEXA, Dental, Optical…. etc. etc.
The “Big” Picture• “Digital” Radiology PACS Digital Radiography MRI Interventional Angio CT Nuclear Medicine Ultrasound
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”
Terminology• RIS (HIS) – Radiology Information System • Transcription, Reporting, Ordering, Scheduling, Billing• PACS – Picture Archiving and Communication System • Acquisition, Interpretation, Storage• Integrated Medical Imaging – RIS, PACS – Integrating the Healthcare Enterprise (IHE)
Integration and Distribution• RIS-PACS Integration – Data Synchronization, Validation – Interpretation & Results Reporting• New Opportunities – Value Added, Patient-less Examination – Computer Aided Diagnosis• Image Distribution (The Internet) – Clinical Review, OR, Patients, Conferences – Enterprise Integration - EMR – Teleradiology
Communication Protocols• TCP/IP – Standard Communications Protocol – The Internet• HL7 – Health Level 7 – RIS / HIS• DICOM 3.0 – Digital Imaging COmmunications in Medicine v3.0 – PACS• HTTP – Hyper-Text Transport Protocol – The World Wide Web
Infrastructure• Platforms • Networking – Clients / workstations – Devices – Servers – Media – Topologies• Physical Plant • Storage – Power – Hardware – software – HVAC – Media – Media – Topologies
Infrastructure Challenges• Business • Technical – Cost vs. quality patient – Lack of qualified technical care professionals – Regulatory compliance – Management of increasing – Access to data across amts of data applications – 100% data integrity & availability• Clinical – Security for data distribution and storage – Information when & where needed – Standards vs. proprietary solutions – Loss or Corruption not tolerated – Impact on patient care
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 Davis 100 BaseT to/from modalities RIS1000 BaseT to database/server/archive Modalities Real-time Customer Care Exam Orders Monitoring HL7 iVault DICOM MWL Storage Mirror Off-Site Backup Emergency Backup Server Enterprise Image Distribution Radiology Reading iSite Enterprise iSite Radiology Internet infrastructure
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
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
UCDMC PACS Database storage Server Spinning disk archive modulesDICOMProcessors &load balancing Current storage:switch 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…….
Unique attribute identification Type 1 = mandatory, non-NULL Group number Type 2 = mandatory, NULL or emptyCharacteristics of module Element number Type 3 = optional Group number even: “standard” odd: “private” From DICOM Part 3: Information Object Definitions
DICOM Attributes• Attributes also have a defined “value representation” Value Tag VR Length Value FieldValue 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 StatementsC-store Don’t assume that desiredC-echo functionality is availableMWL Many capabilities are optional ….. $$Q/RPPS Bottom line:Print Negotiate……… Test and verifySOP classes Work with modality andPrivate tags PACS vendors to achieve desired functionality
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
Radiologist Presentation State Original
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 COMPRESSION• 1 bit = a light switch, ON or OFF, 0 or 1 (2 Values)• 1 byte = 8 bits ‘0000’0000’ to ‘1111’1111’ (256 Values)• 1 Kilobyte (KB) = 1,000 bytes• 1 Megabyte (MB) = 1,000 KB• 1 Gigabyte (GB) = 1,000 MB• 1 Terabyte (TB) = 1,000 GB• 1 Pedibyte (PB) = 1,000 TB• Average Radiology Exam is ~ 20MB• 280,000 Exams = ~ 5.6 Terabytes / year @ UCDMC Radiology
IMAGE COMPRESSION• Average Radiology Exam is ~ 20MB• Lossless Compression - JPEG – ~ 2:1 > 10MB Xfer• Lossy Compression - Wavelet – ~ 20:1 > 1MB Xfer• JPEG 2000 – Combines Lossless techniques and Lossy Wavelet – Finally standards based Wavelet compression – DICOM approval of advanced compression by 2000?
IMAGE COMPRESSION Original 12:1 Wavelet 500 Kbytes 42 KbytesCompression allows more efficient use of limited bandwidth (e.g., telephone modems)
IMAGE COMPRESSION Original 35:1 Wavelet8000 KBytes 230 KBytes
IMAGE COMPRESSION: HOW MUCH? Original Wavelet, 10:1 20:1 40:1How much? ~Visually Lossless ~Clinically Lossless Visible Blur
Courtesy of Nicholas Hangiandreou, Mayo Clinic, Rochester, MN
IMAGE DISTRIBUTION: Web and the Internet Radiology Departments Imaging Imaging Centers Centers CR MRI US CR MRI US CT CTHospitalHospital PCs PCs Clinic Clinic PCs PCs Web Web Control Control Image Image Servers Servers Software Software Archive Archive Office Office (TB) (TB) PCs PCsHomeHome Review Review Review Review PCs Remote Remote Station Station PCs Station Station Radiologists Radiologists Radiologists 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
SUMMARY 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