In the 2D-3D registration problem that we intend to solve here, we try to find the position and orientation of a 3D volume that corresponds to one or more projection images belonging to the intraoperative situation. In our problem the projection geometry is known. The origin of the world coordinate system (WCS) is located between the source and the detector. The source position and detector position and orientation are given in the WCS, as well as the position and orientation of the 3D volumes (which represents our ground truth).
For determining the performance of the registration methods, the 3D volume is repositioned with specific offsets from the ground truth, called the "starting positions". These are the translations in the x, y, and z direction and rotations around the x-, y-, and z-axis, where the centerpoint of the rotation (in WCS) is given per object of interest. The same starting positions (offsets from the ground truth) are used for every object of interest, only the centers of rotation differ. We provide 200 starting positions in the range 0-20 mm mTRE (see [1]).
The dataset includes MR, CT, 3DRX, and fluoroscopic images of 2 spinal segments. Spinal segment 1 consists of 3 vertebral bodies and spinal segment 2 consists of 5 vertebral bodies, in total 8 vertebral bodies to register. Mask images per vertebral body are provided; both 2D masks for the fluoroscopic images and 3D masks for the 3D volumes because some 2D-3D registration methods require masks in the 3D volume and others require masks in the 2D fluoroscopic image. The masks in the 3D volumes of different modalities are directly related because the ground truth is used to make sure that the masks cover the same anatomy in all modalities. 2D and 3D masks should not be used simultaneously because this would bias the method.
The directory structure of the data is given below:
3D image files and 3D mask files (extension .raw)
2D projection files (extension .raw)
2D mask files (extension .raw)
All images contain the voxels in row-column-slice order, meaning that the first voxel in the file should be displayed in the upper left of the screen, the second voxel should be displayed to the right of the first, etc., until the end of the row is reached. The next voxel should be displayed below the first voxel of the file, the next to the right of that, etc., until one complete slice is displayed.
3D image position files (extension .sta (text format))
Source position files (extension .txt)
2D projection position file (extension .rad)
Starting position file (startpositions_200_ordered.txt)
You can find information on 1) how to transform the starting positions to a matrix representing the new 3D position of the volume, and 2) how to attain the result positions from a matrix representing the registered 3D position of the volume in the help page.
[1] E.B. van de Kraats, G.P. Penney, D. Tomazevic, Th. van Walsum, W.J. Niessen, "Standardized Evaluation Methodology for 2D-3D Registration", IEEE Transactions on Medical Imaging, 2005, vol. 24, pp. 1177-1190.