PACS

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PACS
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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)

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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

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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

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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)

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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

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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)

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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 youre sitting and waiting)

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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

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PACS COMPONENTS

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

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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

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PACS Components Storage

• Long Term Storage For archivedstudies

• 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)

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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
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  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 !!

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PACS COMPONENTS

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

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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)