Locate3D Parameters

All of the parameters below are located in the POI Parameters widget.

Centroid Threshold

The relative threshold for identifying pixels that belong to the POI. Once a grayscale region of an X-ray image has been identified as a POI, its centroid is calculated by a weighted average of all the pixels that have an intensity value greater than this percentage (0.0 to 1.0) of the maximum intensity. The default value is 0.25.

Click Search Factor

Used when manually digitizing POIs in the xray images. If you click at point X,Y in an image, a region of the image around this point is searched for the best location of a grayscale centroid. This region is a square centered at X,Y with sides equal to two times the expected radius of the POI times the Click Search Factor. This factor should be set small enough so that the search region includes only the POI you're currently digitizing. The default value is 1.25.

Edge Threshold

The relative threshold for identifying suitable POIs. For a grayscale region in an X-ray image to be considered a POI, the average edge value within the region must be at least this percentage (0.0 to 1.0) of the maximum edge value. The default value is 0.10.

Pose Map Cutoff Frequency

The low-pass cut-off frequency for smoothing the cubic splines in the POI pose maps. The default value is 20.0. Smoothing can be turned off by using a value of 0.0 or less.

Propagation Search Factor

Used when propagating POIs in the X-ray images. In order to propagate a POI with coordinates X,Y in one frame to the next frame, a region of the next frame is searched for the best location of a grayscale centroid. This region is a square centered at X,Y with sides equal to two times the expected radius of the POI times the propagation search factor. This factor should be set large enough so that the search region captures the movement of the POI from one frame to the next, but small enough so that it does not include other POIs. The default value is 2.0.