Locate3D Overview: Difference between revisions
(→Menus) |
|||
Line 264: | Line 264: | ||
:<b>Ctrl-Left mouse key</b>: digitize POI (exact coordinates). | :<b>Ctrl-Left mouse key</b>: digitize POI (exact coordinates). | ||
:<b>Esc</b>: cancel POI digitization. | :<b>Esc</b>: cancel POI digitization. | ||
:<b>Alt</b>: show | :<b>Alt</b>: show weighted center as calculated from current cursor position (becoming position of current POI after clicking left mouse button). | ||
:<b>PgUp/PgDn</b>: moves to the previous/next reporting time. | :<b>PgUp/PgDn</b>: moves to the previous/next reporting time. | ||
:<b>Home/End</b>: moves to the first/last reporting time. | :<b>Home/End</b>: moves to the first/last reporting time. |
Revision as of 17:41, 13 January 2021
Language: | English • français • italiano • português • español |
---|
Locate3D tracks radiopaque beads in X-ray trials. It is most often used to track objects (e.g., bones and implants) with implanted beads. If the object contains three or more beads in fixed locations, and these 3D locations are known relative to the object's CT coordinate system, then the beads' 2D locations in the X-ray images can be used to calculate the object's 3D pose in the X-ray lab frame. Locate3D is thus similar to X4D, except that it uses multiple beads to determine the pose of an object, instead of the contours of the object itself. Locate3D requires that the configuration of the X-ray equipment has been calculated (with CalibrateDSX), and that the locations of the beads in the object's local frame have been determined (with Surface3D).
Digitizing POIs |
---|
To digitize a POI for the current reporting time, select the POI by clicking on its name in the table in the Points of Interest widget. The table row will be highlighted in blue, and when you move the cursor into one of the X-ray windows, the cursor will change to a cyan circle inside a yellow square, with the POI name to the right. The circle represents the expected size of the POI on the X-ray image, which is dependent on the pixel size of the image and the radius of the POI, which is specified in the subject file. The center of the circle is also marked by a cyan point. The square represents the region of the image that will be searched for the center of the POI (some of the outer pixels of the POI can be outside the square). The size of the square is controlled by the Click Search Factor parameter. A larger number makes it quicker and easier to digitize POIs, but you don't want the square to contain more than one POI. When you click the left mouse button, Locate3D will search the X-ray pixels within the square to determine which one is the best candidate for the center of the POI. This is done by using the Centroid Threshold parameter to separate the POI pixels from the background, and the Edge Threshold parameter to determine if these pixels represent a circular POI. The POI is assumed to be a bright circle on a dark background, with the center of the POI being the brightest. The 2D coordinates of the POI center in each view are calculated as the weighted center of the pixels above the Centroid Threshold. Once you digitize the POI in one view (you can start with either view), a yellow line is drawn in the other view. This line is the projection of the point in the first view through the field of view of the second view, and its purpose is to help you identify the POI in the other view. You can then digitize the POI in the second view by clicking on a point near the line. If you make a mistake identifying the proper POI in the first view, you can press the Esc key to cancel the process. If you make a mistake after identifying the POI in the second view, you can remove the POI pose by unchecking the pose box in the POI table. Once you have digitized a POI, Locate3D automatically advances the current POI to the next one in the table that does not already have a pose (unless the Auto-advance box is not checked). Once you have identified the POIs for one or more reporting times, you can have Locate3D attempt to automatically identify them for other reporting times using the Propagate POIs command in the Tools menu. See the wiki entry for this command for more details. Note: If you hold down the Alt key while the POI cursor is displayed over an X-ray image, the cyan point inside the circle will display the location that the centroid-finding algorithm would calculate if you left-clicked with the cursor in its current position. This point will update in real-time as you move the cursor. If the point is not visible inside the yellow square, it means either there is no suitable location of a POI centroid, or that region of the image has been masked by a previously digitized POI. Note: To override the centroid-finding algorithm and digitize a POI at exactly the XY coordinates you click on, hold down the Ctrl key when clicking. While Ctrl is pressed, the yellow square will not be displayed, indicating that the centroid-finding algorithm has been deactivated. This feature can be helpful when digitizing non-circular or overlapping POIs. Note: When digitizing a POI, all previously digitized POIs on the image are masked out, so that no two POIs can be located at the same point. This is done by using the estimated size of each POI on the image to ignore the circular region of pixels around the POI location. This can be especially helpful when digitizing two adjacent POIs in a sequence of frames. If you digitize one of the POIs in all frames first, then propagating the second POI through the sequence is easier because it can't erroneously "lock onto" the first POI's location. |
Tutorials
How To: Track Objects Using Points of Interest
Menus
File Menu |
---|
|
View Menu |
---|
|
Tools Menu |
---|
|
Options Menu |
---|
|
Help Menu |
---|
|
Widgets
DSX Configuration |
---|
|
Points of Interest | ||||
---|---|---|---|---|
Points of interest (POIs) are features of an object that you want to track in X-ray motion trials. They are most commonly used for radiopaque beads implanted in an object whose motion you want to measure. They are distinguished from landmarks, which are object features whose locations you want to calculate once the object pose is known. A common type of landmark is ligament attachment sites. Thus, POIs are used to determine the pose of an object and landmarks are used to calculate locations dependent on the pose. The recommended procedure for adding POIs to an object is to use xManager to create them and specify their names, radii, and colors (for display in the GUI). Then use Surface3D to specify their XYZ locations in the image data (usually CT). It is important that each POI have a correctly specified radius so that Locate3D's circle-finding algorithm can estimate its size in the X-ray images.
|
POI Parameters |
---|
This widget contains the parameters that control the digitization of POIs in the X-ray images. When you are digitizing POIs in the images, there are two methods of determining the XY coordinates in the 2D images, which are then used to calculate the 3D position in the X-ray lab frame. The recommended method is to left-click on any portion of the POI in the image and let Locate3D calculate the weighted center of pixels representing the POI. This process is described in detail in Digitizing POIs, and is governed by the parameters listed below. For cases in which this process does not correctly locate the POI center (e.g., non-circular POIs), you can use Ctrl-left-click to specify the point. In this case Locate3D will use the exact XY coordinates of where you clicked as the 2D location of the POI in that view.
|
POI Graphs |
---|
The POI Graphs widget displays graphs of the X, Y, and Z coordinates of the selected POIs for the current trial. As the cursor is moved around the graph a crosshair shows the current coordinates. If the cursor is close enough to one of the data points for a POI it will snap to it and display that point's coordinates in the POI's color. To move the view of a graph in the Y direction, press the left mouse button and drag the cursor up or down. The mouse wheel can also be used to zoom the graph in the Y direction. Press the R key to reset the graph to the default view. The X axis of the graphs cannot be changed. Data points cannot be added or moved via the graphs, but they can be deleted. To select one or more points, press the Ctrl key and then box-select them (hold the left mouse button down while sweeping the diagonal of a box with the cursor). Press the Delete key to delete the points. Press the Esc key to deselect them. |
X-ray Windows |
---|
The X-ray windows display the X-rays of each view, as well as POIs, POI trails, reference frames, and landmarks. The Points of Interest widget lets you choose which POIs and POI trails to display on the X-rays. The View menu has commands for toggling the display of the reference frame and landmarks of the current object, and the POIs of all of the other objects. The following mouse and keyboard commands can be used in the X-ray windows:
|
Settings |
---|
|