Purpose: To develop an Eclipse script based digitizer for electron cutout using photos of plastic plate templates with cutout outlines, and evaluate the accuracy of the method using simulated images.
Methods: Executable script was developed and tested with Eclipse Scripting API (ESAPI). Multiple testing cases were generated on transparent plastic plate templates of all available sizes. Experimental outlines of cutouts were contoured on the plates, and photos were taken with the camera central axis pointing to the plate at a relatively vertical angle and at least 50cm away from the surface of the plate. The images were stored electronically in .jpg format with standard pixel size and default compression settings. The testing photos were read by the script and displayed in a Graphical User Interface (GUI). The four corners of the template were manually picked to establish a projective transformation mapping the pixels in the photo to the corresponding positions in the Beam Eye View (BEV) of electron beams. The cutout contours were then semi-manually (automatically if the photo was taken with white background) digitized in the 2D domain of BEVs for the generation of electron cutouts.
Results: 10 testing photos have been generated and digitized to generate electron cutouts importable to treatment plans in Eclipse. The projective transformations have been successfully established for all testing photos. Cutout outlines were digitized with acceptable accuracy (max difference <2mm) for testing cases.
Conclusion: The script-based digitization provided a free and reliable alternative solution for the generation of electron cutout from plastic templates. The accuracy of the method has been verified on limited set of testing cases. For following work, the script will be revised to make the digitization process more automated, and clinically used electron cutouts with more complicated shapes will be re-digitized to further validate the accuracy of the method.