Basic Principles of PACS Networking

1
Basic Principles of PACS Networking

• Emily Seto
• Medical Engineering/SIMS
• Center for Global eHealth Innovation
• April 29, 2004

2
Overview

• PACS Introduction
• PACS Network Related Concepts
• Network Lingo and Relevance to PACS
• Example of PACS Network
• Take Home Message

3
What is PACS?
PACS Picture Archiving Communications System
System facilitating viewing storage of digital
medical images
4
Medical Digital Images
X-RAY BASED
Mammography
Nuclear Med (PET)
Light
CR
Fluoroscopy
5
PACS
Acquisition
Processing
Storage
Viewing
HIS
RIS
6
PACS Network Related Concepts
7
Reliability/Security

• Mirrored systems separated by physical distance
• Archived data
• Redundant paths (consider direct path from
  acquisition device to particular PACS PC)
• 24/7 Support (access network remotely)
• Secure lines outside of hospital to view images
• eg via Virtual Private Network from physicians
  homes

8
Speed

• Online, Near-line Disaster Recovery Back-ups
• Prefetching autorouting (pushing images)
• Local copy vs streaming data
• Bandwidth (dedicated LAN)

9
Compression

• Lossy vs non-lossy (up to 31)
• Acceptable compression different for each type of
  image
• Different types (eg wavelet, jpeg)

318 kB
101 (30 kB)
1001 (4 kB)
10
Network Lingo and Relevance to PACS
11
Local Area Network (LAN)

• Computer network that spans relatively small area
• Can be desirable to have dedicated PACS LAN for
  all PACS devices (acquisition devices, display
  workstations, storage, and servers)
• Advantages
• Helps ensure adequate bandwidth
• Can aide in device management

12
Redundant Array of Independent (or Inexpensive)
Disks (RAID)

• Combination of multiple disks drives to improve
• Performance
• Data striping (spread out blocks of each file
  across multiple disks)
• Fault tolerance
• Disk mirroring
• Dedicated disk for error correction
• 50 of hardware device failures are due to disk
  failures

13
Network Attached Storage (NAS)

• Storage device taken away from server and
  directly connected to network
• Devices assigned IP addresses and accessed by
  clients via a server (gateway to data) or
  accessed directly by clients

14
NAS Advantages

• Centralized storage, security, management, and
  data back-up
• Servers running different operating systems can
  all access data
• Expandability (add new device without shutting
  down servers)
• Fault tolerance (server fails can still access
  data)

15
Storage Area Network (SAN)

• High-speed sub-network of shared storage devices
• Access data via server systems connected to both
  the LAN and SAN

16
SAN Advantages

• Centralized storage, modular scalability, high
  availability, and increased fault tolerance
• Removes bandwidth bottlenecks with LAN based
  server storage
• Serverless backup (high speed data backup without
  using LAN bandwidth)

17
Example of NAS/SAN
Image Acquisition Devices
Non-compressed Deep Archive
1
Load-Weighted Servers
Tier 1 Storage -redundant paths out -connected
by fiber optic cables -most recent
studies -non-lossy compression
2
3
Tier 2 Storage -compressed (lossy) -older studies
4 (2 months later)
Image Display
NB Entire system should be mirrored offsite
18
Networking Budget

• Mirrored servers storage (several Terabytes)
• Archiving (magneto-optical tapes, DVD-ROMs,
  CD-ROMs, etc.)
• Petabyte (1024 Terabytes)
• Proper facilities to house servers storage
• Network infrastructure (network drops, cable,
  etc)
• Support

19
Take Home Message

• Each institution will have their own PACS
  networking needs depending on size, type and
  volume of images, existing network, and budget
  available
• Main concepts to keep in mind
• Reliability/Security
• Speed
• Compression

20
?
Contact Info Emily Seto
emily.seto_at_uhn.on.ca [phone] x6409