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OpenIGTLink 3D Slicer: Bidirectional Video Streaming with AI Segmentation#

Authors: Holoscan Team (NVIDIA)
Supported platforms: x86_64, aarch64
Language: Python, C++
Last modified: October 9, 2025
Latest version: 1.0
Minimum Holoscan SDK version: 1.0.3
Tested Holoscan SDK versions: 1.0.3
Contribution metric: Level 2 - Trusted

This application demonstrates how to interface Holoscan SDK with 3D Slicer, using the OpenIGTLink protocol. The application is shown in the application graph below.

In summary, the openigtlink transmit and receive operators are used in conjunction with an AI segmentation pipeline to:

  1. Send Holoscan sample video data from a node running Holoscan SDK, using OpenIGTLinkTxOp, to 3D Slicer running on a different node (simulating a video source connected to 3D Slicer):
    • For cpp application, the ultrasound sample data is sent.
    • For python application, the colonoscopy sample data is sent.
  2. Transmit the video data back to Holoscan SDK using OpenIGTLinkIF Module, and receive the data with the OpenIGTLinkRxOp operator.
  3. Perform an AI segmentation pipeline in Holoscan:
    • For cpp application, the ultrasound segmentation model is deployed.
    • For python application, the colonoscopy segmentation model is deployed.
  4. Use Holoviz in headless mode to render image and segmentation and then send the data back to 3D Slicer using the OpenIGTLinkTxOp operator.

This workflow allows for sending image data from 3D Slicer over network to Holoscan SDK (running on either x86 or arm), do some compute task (e.g., AI inference), and send the results back to 3D Slicer for visualization. Nodes can run distributed; for example, Holoscan SDK can run on an IGX Orin (Node A) sending the video data, 3D Slicer on a Windows laptop (Node B) and the AI inference pipeline on yet another machine (Node C). Also, note that the openigtlink operators can connect to any software/library that supports the OpenIGTLink protocol; here, 3D Slicer is used as it is a popular open source software package for image analysis and scientific visualization.

For the cpp application, which does ultrasound segmentations the results look like

and for the python application, which does colonoscopy segmentation, the results look like

where the image data before Holoscan processing is shown in the left slice view, and the image data with segmentation overlay (after Holoscan processing) is shown in the right slice view.

Run Instructions#

Machine running 3D Slicer#

On the machine running 3D Slicer:

  1. In 3D Slicer, open the Extensions Manager and install the SlicerOpenIGTLink extension.
  2. Next, load the scene openigtlink_3dslicer/scene/openigtlink_3dslicer.mrb into 3D Slicer.
  3. Go to the OpenIGTLinkIF module and make sure that the SendToHoloscan connector has the IP address of the machine running Holoscan SDK in the Hostname input box (under Properties).
  4. Then activate the two connectors ReceiveFromHoloscan and SendToHoloscan (click Active check box under Properties).

Machine running Holoscan SDK#

On the machine running Holoscan SDK:

  1. Configure the connection: Update the host_name parameters in the configuration files for both OpenIGTLinkRxOp operators:
  2. openigtlink_tx_slicer_img
  3. openigtlink_tx_slicer_holoscan

Set these to the IP address of the machine running 3D Slicer.

> **Note**: This application requires [OpenIGTLink](http://openigtlink.org/) to be installed.

  1. Run the application: Use the Holohub CLI to launch the application.

  2. For the python application:

    ./holohub run openigtlink_3dslicer --language python

  3. For the cpp application:

    ./holohub run openigtlink_3dslicer --language cpp