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PACS

PACS. What is PACS ?. P icture A rchiving and C ommunications S ystem (actually more than name implies) PACS provides the ability to electronically (ie, computer and network technology) to: Input images from (digital) modalities Distribute images to PCs and workstations

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PACS

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  1. PACS

  2. What is PACS ? • Picture Archiving and Communications System (actually more than name implies) • PACS provides the ability to electronically (ie, computer and network technology) to: • Input images from (digital) modalities • Distribute images to PCs and workstations • Read on computer display (diagnostic & clinical) • Store (both long and short term) images • Transmit (to other areas or off-site)

  3. Reasons for PACS • More Efficient Workflow: • RTs spend up to 50% of time “handling” film • Reader cannot effectively interpret exams on film consisting of hundreds of images (eg, MSCT) • Faster Medical Care Delivery: • Images available to reader at exam completion • Clinical consults possible via remote access • Potential Cost Savings: • Eliminate lost film • Improved productivity • Eliminate lost film preventing lost revenue

  4. PACS COMPONENTS • Network (to acquire/distribute/transmit) • Servers (to maintain/control database) • Storage (secondary storage devices) • Short term (current studies) • Long term (archives) • Workstations (reading and clinical review) In many cases, specials requirements for PACS push the limits of technology

  5. PACS Basics: “Size” of Studies Useful Facts and Terms to Know: • 1 K x 1 K = 1 M (eg, 2K x 1.5 K = 3 M) • 1 K x 1 M = 1 G (Gig), etc • Digital images consist of a “matrix” of “pixels” • Each pixel contains a binary number representing the gray level of the pixel • One or two bytes/pixel • One: (US, NM) • Two (CT, MR, DR)

  6. PACS Basics: “Size” of Studies • Example 1: 4-View Digital Radiography Exam: • 2K x 2.5K matrix: 2K x 2.5K = 5 MegaPixels (MP) • 5 MP x 2 bytes/pixel = 10 Megabytes (MB)/Image • 4 images/exam x 10 MB/image = 40 MB/Exam • Example 2: Average CT Exam (300 images): • 512 x 512 matrix: 0.5K x 0.5K = 0.25 MegaPixels • 0.25 MP x 2 bytes/pixel = 0.5 Megabytes/image • 300 images/exam x 0.5 MB/image = 150 MB/exam • Example 3: Large CT Exam (1200 images): • 0.5 Megabytes/image (same as above) • 1200 images/exam x 0.5 MB/image = 600 MB/exam

  7. PACS Components: Network • “Communications” part of PACS: • Acquire/ distribute/transmit images • Entirely “standards” based • Network Hardware: • Ethernet (most common) using 10- or 100-Base T • Gigabit (1000Base-T) & Fiber channel “backbones” • Protocols and Software: • Network protocol: TCP/IP (the Internet Standard) • Image Formats: DICOM 3 (this is key)

  8. PACS Components: Network Issues • Average CT Exam (150 MB) on 100-Base T • 100 Base-T: maximum 100 Mbits/sec (60 average) • 150 Mbytes x 8 bits/byte = 1200 Mbits • 1200 Mbits/60 Mbits/second = 20 seconds • Large CT Exam (600 MB) on 100-Base T • 100 Base-T: maximum 100 Mbits/sec (60 average) • 600 Mbytes x 8 bits/byte = 4800 Mbits • 4800 Mbits/60 Mbits/second = 80 seconds (seems like forever if you’re sitting and waiting)

  9. PACS COMPONENTS • Network (to acquire/distribute/transmit) • Servers: maintain/control database(database is the exam directory: patient demographics, what exams performed and when, where the images are stored, etc): • Must maintains database for 5 or more years • Size and speed requirements depend on facility • May have multiple servers to share duties • May have “mirrored” servers for high availability

  10. PACS COMPONENTS • Network (to acquire/distribute/transmit) • Servers (to maintain/control database) • Storage (using secondary storage devices) • Short term (current studies): • Long term (archives)

  11. PACS Components: Storage • Short Term Storage: • For current studies (and relevant prior studies) • Need fast retrieval: when reader selects exam to read, server must deliver it within seconds • Most Common: RAID • Typically need 3-4 weeks of short term storage • Prefer to have ~ 1 year (rapid access to priors) • Actual amount is cost/performance trade-off

  12. PACS Components: Storage • Long Term Storage: For “archived”studies • Speed not as critical (usually exams pre-fetched) • Must have copies at two sites (JCAHO, HIPAA) • Need to archive at least 5 years (CT state law) • Type of archive basically cost/speed tradeoff • Archive Technologies: • Hard disk based: fastest, most expensive • DVD: intermediate speed, moderate cost • Tape (DLT, LTO, etc): cheap but slow (reliable??) • Offsite archiving (Service Provider)

  13. PACS Storage Issues: Data Volume • Volume of Radiology Data (HH): • CT: 40,000 exams x 150 MB/exam = 6 Terabytes • Radiography: 75,000 x 40 MB/exam = 3 Terabytes • All others: 1 Terabyte TOTAL: 10 TB/years • Archive Requirements: • 5 years x 10 TB/year = 50 Terabytes Note: 50 TB = 51,200 Gigabytes !! 50 TB = 52,428,800 Megabytes !!

  14. PACS COMPONENTS • Network • Servers • Storage • Workstations • reading/clin view • usually high end PC • Diag: 2-4 monitors • Often 3rd monitor (for color/text)

  15. PACS Components: Workstations • Diagnostic Workstation: (for radiologists) • Diagnostic Quality Displays (expensive) • Very High Resolution: • 2K x 1.5K for radiography (1280x1024 max-avg PC) • 2K x 2.5K common (required for digital mammo) • Very High Brightness: to display graylevels • 10 bits/pixel (1024 graylevels displayed • 700 cd/m2 (70-120 for normal CT monitor)

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