X4D Overview
Contents
X4D tracks 3D objects (bones, implants, etc.) in X-ray images by generating digitally reconstructed radiographs (DRRs) of the objects and matching them to the X-ray images. It requires that the 3D X-ray configuration parameters be defined in the subject file and that the X-ray images be corrected.
To match DRR images to X-ray images, both sets of images are processed first. X-ray images are smoothed with a convolution filter, and then an edge detection algorithm is performed on them. The final processed X-ray image that is used for tracking is the edge detection image times a weighting factor, plus the smoothed intensity image. DRR images are not smoothed, but are input to the edge detection algorithm. The final processed DRR image is the edge detection image time a weighting factor, plus the original DRR image.
X4D has a job batch option, enabling multiple tracking optimizations to be run without user intervention.
Tutorials
Bone Tracking
4D Optimization
Matching Xray and DRR Images
Motion Capture Data
Working with Motion Capture Data
Image Metrics
The measurement used by the optimization algorithm to compare the X-ray and DRR images during object tracking.
Pixel Difference
Conditional Entropy
Save Pose Maps This command saves the pose map of each selected object in the current trial to a .csv file. This file contains 6 values for each pose: the XYZ translation and the XYZ Euler angles representing the transform from the X-ray lab frame to the object's local coordinate system (i.e., as if you were traveling from the lab frame to the object frame). If a name for the pose map file is not already specified in the subject file, you will be prompted to browse for the file to create. A link to this file will then be added to the subject file.
Save Object Transforms This command saves the pose map of each selected object in the current trial to a .txt file. This file contains a 4×4 transform for each pose, expressing the transform from the X-ray lab frame to the object's local coordinate system (i.e., as if you were traveling from the lab frame to the object frame). If a name for the transforms file is not already specified in the subject file, you will be prompted to browse for the file to create. A link to this file will then be added to the subject file.
Save Landmarks This command saves the locations in the X-ray lab frame of each selected object's landmarks in the current trial to a .txt file. This file contains a set of landmark coordinates for each pose in the pose map. If a name for the landmarks file is not already specified in the subject file, you will be prompted to browse for the file to create. A link to this file will then be added to the subject file.
Export Poses to CMZ This command exports the pose map of each selected object in the current trial to the session's CMZ file. If the CMZ already contains poses for these objects for this trial, those poses will be removed before the current ones are exported. This command does not affect the poses of unselected objects, nor of other trials in the CMZ file. If a CMZ file is not already specified in the subject file, you will be prompted to enter the name of a new one.
DSX Configuration (Ctrl + Shift + C) toggles the appearance of the dockable DSX Configuration widget, which lets you select sessions, configurations, trials, and objects.
3D View (Ctrl + Shift + V) toggles the appearance of the dockable 3D View window, which displays the X-ray configuration, selected objects, and mocap markers.
Image Optimization (Ctrl + Shift + I) toggles the appearance of the dockable Image Optimization widget, which can be used to optimize the X-ray, DRR, and image metric settings to better track objects in the X-ray images.
This menu provides the same functionality as the Pose Maps widget.
DSX Configuration
X-ray and DRR Settings
Pose Maps
Object Tracking
Image Optimization
Graphs
Mocap Model
3D View
X-ray Windows
Optimization Job Queue
Output Window
Settings
Select GPUs