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Subsections

20. The VVLink Tool

20.1 Introduction

**Figure 20.1:** The BrainLAB VectorVision Cranial Image-Guided Surgery Application.

In collaboration with BrainLAB AG we have performed work to integrate research image analysis methods and software with a commercial image guided surgery navigation system (the BrainLAB VectorVision Cranial System.) This work was described in a recent conference paper [83] - see also Markus Neff's Master Thesis [68]. The integration was achieved using a custom designed client/server architecture termed VectorVision Link (VV Link) which extends functionality from the Visualization Toolkit. VV Link enables bi-directional data transfer such as image data sets, visualizations and tool positions in real time. This page describes the VVLink Tool of BioImage Suite which is the module that handles the communication with the VectorVision Cranial (VVC) system.

Note: The snapshots in this document were taken from a prototype version of VVC that was made available us during the design phase of VVLink. The released version of BioImage Suite (Windows and Linux platforms only) is, however, designed to communicate with the commercially available newly released VVC 7.8 - the actual user interface for VVC 7.8 is slightly different.

20.2 The BioImage Suite VVLink Interface

**Figure 20.2:** Accessing the BioImage Suite VVLink Tool (left) and defining VVC Servers (right).

If available and enabled (using the Preferences Editor under Advanced/Miscellaneous), the VVLink tool is accessible under the Features menu as shown in Figure 20.2.

The first step in using the VVLink tool is to connect to a VVC host machine (typically an Image-Guided surgery system). Each host is defined by three values, namely a description, the hostname (or IP address), and its password. Server configurations are saved in a filed called ``.vvlinkservers'' in the user's home directory, and are displayed in the drop-menu titled ``server'' in the ``Server''-tab of the VVLink Tool. This tab is highlighted using a dotted ellipse in Figure 20.2 (left,bottom).

If no servers have been defined then click on the Add New Server button. This action brings up the dialog box shown in Figure 20.2 (right, bottom). The server password is obtained from the VVC system under Tools-VVLink as shown in the snapshot in Figure 20.2 (right, top). The Server configuration may be loaded and saved using the Re-Load Setup and Save Setup buttons respectively.

20.3 Connecting and Transferring Images

**Figure 20.3:** Transferring Images from the VVC system to the BioImage Suite VVLink Tool.

Once the server is defined, the next step is to connect to it. This is accomplished using the Connect button, next to the ``Server'' drop-menu. If the connection is successful, the VVLink Tool will download a list of available images in the VVC System as shown in Figure 20.3. Also the VVLink Tool will be redrawn with a red frame as opposed to a black frame. (Compare Figures 20.2 and 20.3).

Note: VV Cranial needs to (a) be configured to allow connections from the specific machine as it uses IP address filtering (change the variable AllowedSubnets in the configuration file vvcranial.ini, and (b) to enable the VVLink Interface. Consult the VV Cranial documentation for more details. In this particular example (Figure 20.3), there is only one image in the system, although more may appear. To enable proper communication between VVCranial and BioImage Suite, the user must next transfer an image. Transferring an image establishes the coordinate transformations between the two systems. To transfer an image, first select it in the list titled ``Current VectorVision Image List'' and then transfer it using the Transfer button. Most images transfer successfully using the ``Auto-detect'' settings. If the orientation (axial, coronal, sagittal) is wrong, the correct orientation may be manually set. Should the image need to be flipped about any of coordinate axis (use this with care! ) use the Advanced button to bring up the advanced controls (Figure 20.3 right) and set parameters appropriately.

20.4 The Data ``Tab'', Saving Images and Transformations

**Figure:** Images and Transformations obtained from the VVC system.

If the image transfer operation was successful, the information transferred (the image and its associated transformation to the world coordinate system) are placed in two controls on the ``Data''-tab shown in Figure 20.4. The image is also displayed in the viewer associated with the VVLink Tool.

Both the image and the transformation can be manipulated (Load/Save etc.) using the options in their respective controls.

The transformation is used to map points in the world coordinate system (i.e. the operating room coordinate system) defined by the BrainLAB VVC system following patient to image registration to the image coordinate system, so that tools tracked in the VVC system can be appropriately displayed in BioImage Suite.

20.5 Real Time Communication

**Figure:** ``Link''-tab in VVLink Tool, which facilitates both streaming visualizations and linking the BioImage Suite viewer cursor (cross-hairs) to the surgical navigation pointer.

There are two aspects to the real-time communication functionality made available in the ``Link''-tab (see Figure 20.5.), (i) streaming visualizations and (ii) linking the viewer cursor with the surgical navigation pointer.

20.5.0.0.1 Streaming Visualizations

VV Cranial has the ability to take as an input a stream of bitmaps and display them within the VVC interface. (See the paper for examples) We have implemented functionality in BioImage Suite to capture the current viewer display and make it available to VV Cranial as such a bitmap stream. The user interface for this is located in the top half of the ``Link''-tab.

The connection can be tested using the Test button and then, if desired, enabled using the Enable button. Once enabled BioImage Suite will send a stream of snapshots from the attached viewer at a rate determined by the setting of the Input Update Time drop-menu. This can be stopped using the Disable button. Please note, that streaming visualizations requires that the client machine (i.e. the computer running BioImage Suite) is computationally powerful enough to handle this operation.

The streaming visualizations are accessible in VV Cranial under the ``Info View'' tab of each VV Cranial Viewer.

20.6 Obtaining and Transferring the position of Tools and Landmark points

**Figure 20.6:** The ``Points''-tab in VVLink Tool, which has functions for saving the current positions of tracked tools, the locations of labeled landmarks, and for acquiring landmark points in the Landmark Control using the surgical navigation pointer.

The VVLink Tool can extract ``labeled point'' positions and tracked tool positions from the VVC System using VVLink. These can be acquired and stored using one of three methods:

Landmarks - pressing either the Get Labeled Points As Landmarks button or the Get Tracked Tool Tips As Landmarks button. This action places the landmarks in the clipboard of the Landmark Control. These landmarks can next be pasted into any pointset using the ``PointSet-Paste'' option from the Landmark Control menu. The Landmark Control is accessible using the Landmark Control button towards the bottom of the ``Points''-tab.
Surfaces - by pressing either the Get Labeled Points As Surfaces or the Get Tracked Tool Tips As Surfaces buttons. This action places the surfaces in the clipboard of the Surface Control. These surfaces can be pasted into any pointset using the ``Edit-Paste'' option from the Surface Control menu. The Surface Control is accessible using the Surface Control button towards the bottom of the ``Points''-tab.
Text Files - by pressing either the Save Labeled Points in Text File or the Save Tracked Tools in Text File buttons. The Save Tracked Tools option does not ask for a filename to eliminate any unnecessary delays. Instead, it simply saves the tools in a file titled tools_time.txt in the current directory, where time is the current time, e.g. tools_162339_13Jul2006.txt. The current directory can be set using the Switch Directory option under the File menu of the current viewer.

In addition the Add Landmark button (or pressing Ctrl-L) can be used to capture a landmark from the current position of the surgical navigation pointer and place it in the Landmark Control, in a similar manner to clicking the mouse (shift-click) in the BioImage Suite viewer.

The Z-touch and Strip tabs which appear in the screenshots are Beta Features and may not be present in your version of BioImage Suite. They are not supported as they stand.

Next: 21. The Differential SPECT Up: 6 F. Neurosurgery Tools Previous: 19. Intracranial Electrode Localization Contents