Image
Guided
Systems
Inter
Operability

Advancing open-source image guided systems through cooperation and collaboration.

Mission

The IGSIO was founded after lengthy discussions regarding the standardization of tracked ultrasound communication to work towards improving the interoperability between industrial products and research software platforms [1]. Prior to these discussions, the commonly accepted solution was to pass specially constructed messages over the OpenIGTLink protocol. This workaround solution indicated that a more formal definition was needed to enable the research community to move towards a vision held by the founding members.

The mission of the IGSIO is to develop a written standard defining the communication of tracked ultrasound systems between software platforms and to produce an open-source reference implementation of an OpenIGTLink client and server for use by any adhering software platform.

Goals

We seek to achieve the following goals:

Founding Members

IGSIO was founded at the NAMIC 2016 Winter Project week in Cambridge, Massachusetts. Founding members include:

The Standard: Tracked Ultrasound over OpenIGTLink (TUO)

The standard is presented here as a draft. Extensions to the OpenIGTLink protocol have been proposed here and implementation of these extensions is underway here.

Standard Draft


Revision 0.2 (winter 2017) of the Tracked Ultrasound over OpenIGTLink (TUO) protocol is presented.

The communication protocol


A client and a server connects over OpenIGTLink. Messages can be then be sent both ways. To request information a query is sent.

Queries and their response are handled by the COMMAND message, introduced in the OpenIGTLink v3 standard. The information requested is passed using the other types of messages. Every query (COMMAND) should result in a respons (RTS_COMMAND) and optionally one or more other message types. All message types are specified in the OpenIGTLink standard v3.

The COMMAND message has a command name. There are 4 command names defined: Get, Set, Subscribe and Unsubscribe. The command name is specified in the COMMAND messages command_name field. The body of the COMMAND message contains a content field which will specify what kind of information is requested. The content is structured using xml tags.

Command names

"Get" requests information one time, like the depth setting of the scanner. "Set" requests setting for example a parameter on a scanner. "Subscribe" and "Unsubscribe" requests to start or stop getting continuous updates, for example getting updates when the depth setting is changed.

Examples


Here are some examples illustrating how to request information using this standard and what respons to expect. [ TYPE=..., device_name=... ] contains the message type to be sendt and specific fields from the message header or body. The content of the COMMAND message is specified below the [ TYPE=..., device_name=... ] field.

Get

Request getting information of a certain type.

Example 1:

Query: "Get the values for depth and gain."

[ Type = COMMAND, device_name = name, command_name = Get ]
<Command>
    <Parameter Name=”Depth” />
    <Parameter Name=”Gain”  />
</Command>

Respons: "You can get the depth value, but not the gain value."

[ Type = RTS_COMMAND, device_name = name, command_name = Get ]
<Command>
  <Result success=true> <Parameter Name=”Depth” /> </Result>
  <Result success=false> <Parameter Name=”Gain” /> </Result>
</Command>

Information: "Here is the depth value."

[ Type = STRING, device_name = name ]
<Parameter Name=”Depth” Value=”45” />
Example 2:

Query: "Get the functionality of the server's current configuration."

[ Type = COMMAND, device_name = name, command_name = Get ]
<Command>
    <Capabilities />
</Command>

Response: "You can get the servers capabilities."

[ Type = RTS_COMMAND, device_name = name, command_name = Get ]
<Command>
    <Result success=true> <Capabilities /> </Result>
</Command>

Information: "Here are the server capabilities."

[ Type = STRING, device_name = name ]
<Capabilities>
  <UltrasoundCapabilities>
    <Probes>
      <Probe name="L14-5/38"/>
      <Probe name="C5-2/42"/>
    </Probes>
    <ImagingModes>
      <ImagingMode Name=”b-mode+angio”>B-Mode,Angio</ImagingMode>
    </ImagingModes>
    <Streams>
      <Stream name="B-Mode">
        <Parameters>
          <Parameter name="depth" min="5" max="220" step="5"/>
        </Parameters>
      </Stream>
      <Stream name="Angio">
        <Parameters>
          <Parameter name="depth" min="5" max="220" step="5"/>
        </Parameters>
      </Stream>
    </Streams>
    <Presets>
      <Preset name="Vascular small object B+Angio">
        <Probe Name=”L14-5/38” />
        <Parameter Name=”Depth” Value=”50” />
      </Preset>
    </Presets>
  </UltrasoundCapabilities>
</Capabilities>
Set

Request setting information of a certain type.

Example 3:

Query: "Set the us scanners depth and gain values."

[ Type = COMMAND, device_name = name, command_name = Set ]
<Command>
    <Parameter Name=”Depth” Value=45 />
    <Parameter Name=”Gain” Value=35 />
</Command>

Respons: "Setting depth was a success. Setting gain was not a success."

[ Type = RTS_COMMAND, device_name = name, command_name = Set ]
<Command>
  <Result success=true> <Parameter Name=”Depth” /> </Result>
  <Result success=false> <Parameter Name=”Gain” /> </Result>
</Command>

Information: "Here are the current values for depth and gain. (Depth was changed, but not to the exact requested value. Gain was not changed.)"

[ Type = STRING, device_name = name ]
<Parameter Name=”Depth” Value=”40” />
<Parameter Name=”Gain” Value=”30” />
Subscribe

This will cause the server to send information of the requested type each time the information changes.

Example 4:

Query: "Subscribe to changes in depth. Subscribe to new images."

[ Type = COMMAND, device_name = name, command_name = Subscribe ]
<Command>
    <Parameter Name=”Depth” />
    <Image />(*)
</Command>

(*) maybe we do not want to allow asking for more than one type of information in a single command

Respons: "Subscribing to both depth and image was a success."

[ Type = RTS_COMMAND, device_name = name, command_name = Subscribe ]
<Command>
  <Result success=true> <Parameter Name=”Depth” /> </Result>
  <Result success=true> <Image /> </Result>
</Command>

Information: "Here are the changing depth values and new images."

[ Type = STRING, device_name = name ]
<Parameter Name=”Depth” Value=”40” />

[ Type = IMAGE, device_name = name ]

[ Type = IMAGE, device_name = name ]

[ Type = STRING, device_name = name ]
<Parameter Name=”Depth” Value=”50” />

[ Type = IMAGE, device_name = name ]

[ Type = IMAGE, device_name = name ]
...
Unsubscribe

This will cause the server to stop sending information of the requested type.

Example 5:

Query: "Unsubscribe to images."

[ Type = COMMAND, device_name = name, command_name = Unsubscribe ]
<Command>
    <Image />
</Command>

Respons: "Unsubscribing was a success. You will no longer get new images."

[ Type = RTS_COMMAND, device_name = name, command_name = Unsubscribe ]
<Command>
  <Result success=true> <Image /> </Result>
</Command>
Parameters

Ultrasound imaging devices have parameters that can be changed. The OpenIGTLinkIO standard defines a set of parameters that are common to the majority of such devices. Anyone implementing support for a new hardware device using the OpenIGTLinkIO standard should add support for the following parameters.

Parameters can be queried using the COMMAND message as explained under the communication protocol.

Read-write parameters

Read-only parameters

Links

  1. 2016_Winter_Project_Week/Projects/TrackedUltrasoundStandardization
  2. 2016_Summer_Project_Week/Projects/TrackedUltrasoundStandardization
  3. 2017_Winter_Project_Week/Tracked_Ultrasound_Standardization
  4. http://openigtlink.org/protocols/v3_proposal.html
  5. https://github.com/IGSIO/OpenIGTLinkIF