DICOM%20Configuration

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DICOM Configuration

• Robert Horn, Agfa Corporation

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Supplement 67

• Existing Industry Protocols
• NTP (Network Time Protocol)
• DHCP (Dynamic Host Configuration Protocol)
• DNS (Domain Name System)
• LDAP (Lightweight Directory Access Protocol)
• Existing Configuration Tools
• Existing support databases
• DICOM specific information model for LDAP
  databases

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DICOM Configuration Goals

• Support New Functions
• Security and Privacy
• Synchronized Multi-device Acquisitions
• Reduce Operational Costs
• Network Administration
• AE-Title management
• Service location management
• Feature location management

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Time Synchronization

• For
• Multi-device simultaneous acquisitions
• Cardiac Catheterization laboratory
• Coordination
• Security Logs, Procedure Logs
• Convenience

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Synchronization Specification

• Specify error relative to time reference(s)
• Acceptable absolute time error (relative to UTC)
• o( 1s ) security logs
• o( 100s ) cardiac catheterization
• Acceptable synchronization error within a Time
  Source (0018,1801) (relative to local source)
• o( 1s ) security logs
• o( 10ms) cardiac catheterization (a few percent
  of one cycle of a rapidly beating heart).

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NTP - Network Time Protocol

• Widely available
• Suitable for both low precision time and high
  precision time synchronization
• SNTP (Simple NTP) clients for low precision and
  limited capability systems.
• Extensively documented and explained on
  www.ntp.org

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Accuracy capability of NTP

• o(1s) Either client (NTP,SNTP), network
  capable OS, Internet, GPS, or radio
  connection
• o(250ms) NTP client, interrupt driven OS, NTP
  clock controls
• o(100ms) local network topology
• o(10ms) OS clock, OS design
• o(1 ms) OS/application design, network
  topology
• o(100 us) Hardware assist, OS/application design
• o(10 us) Instrumentation clock, custom OS
• o(1 us) Atomic clock, extensive hardware
  assist

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How NTP works
Query Time Sent (Ta)
Response Time Query Received (Ti) Time Response
Sent (Tj) Current Time Parameters (TP)
Redundant Servers
NTP Server
Client Provides Old Network Parameters Old Time
Parameters
Query
Response
Mathematical Magic happens
Client Sets and Fine Tunes System Clock
SNTP performs only the clock setting NTP includes
the network delay estimation, optimal
estimation mathematics and fine tuning of
the system clock.
NTP Client
NTP clients may utilize redundant servers
NTP clients may utilize instrumentation grade
pulse generators (e.g. Atomic Clocks)
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Typical NTP configurations
Internet
NTP Server
GPS Receiver
Campus Network
NTP Clients
Switching Hub
Local NTP Server
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Network admin

• DHCP (Dynamic Host Configuration Protocol)
• Assigns IP address, hostname
• Informs DNS of assignment
• Provides routing, NTP, DNS, etc. information to
  client
• DNS (Domain Name System)
• Provides hostname to IP lookup services
• Provides server location lookup services
• LDAP (Lightweight Directory Access Protocol)
• Provides simple information directory services

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DHCP

• Widely used
• Support stable IP allocation (needed for
  transition and legacy equipment)
• Supports dynamic IP allocation
• Understood by IT administrators
• Documents network IP configuration in file
• Devices only need their "name"

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DNS

• Widely used
• Provides translation from hostname to IP
• DHCP uses DDNS option to maintain coordination
  with dynamic IP assignments
• RR SRV records provide location of LDAP server

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LDAP

• Widely used (known as Active Directory in
  Windows)
• Simple query oriented network database
• Simple information model. Schema provided as
  part of Supplement 67.
• Alternatives examined
• CIM very attractive, but a much larger effort to
  define and implement. Not yet widely used.
• SNMP, DMTF interesting but deal with different
  aspects of network administration and management.

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Locate AE-title (internal operation)
LDAP Server
Where is AE-X
AE-X is at hostname, port
Database
Where is hostname?
DNS Server
Hostname is x.y.z.w
DICOM Traffic
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Beyond Finding AE-Titles

• Installation and Network Configuration oriented
• AE Configuration
• Obtain new unique AE-Title
• SOP Classes supported (SCU/SCP, Transfer
  Syntaxes)
• IHE Actor
• Vendor extension
• Device Configuration
• Description
• Vendor extension
• Hospital extension

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Pre-configured Installation

• Large network addition
• Multiple vendors
• Reduce coordination and scheduling delays
• Reduce configuration errors
• Reduce staging requirements

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Pre-configured Installation
Vendor A Preparation
LDAP
LDIF
Prepared Configurations
IT Organization
DHCP
Network Planning
A
A
LDIF
A
Prepared Configurations
A
B
B
B
Vendor B preparation
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Add another machine
Get IP, hostname, etc.
DHCP
Install Hardware
Find LDAP Server
Assign Name
DNS
LDAP
Query Configuration
Configure System
Obtain Unique AE Titles
Update Configuration
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Hospital network reconfiguration
DHCP Server
Shutdown (DHCP)
Revise DHCP Configuration
Resume DHCP
Modify network hardware
Clients Resume
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Customer Assisted Maintenance

• Simple device swap
• Remote reconfiguration
• Local reconfiguration