The ray tracing window is used to verify Plaque Simulator's dosimetry ray tracing algorithms. The table lists the different materials that Plaque Simulator keeps track of and their radiation intensity attenuation relative to that of water along the linear path length crossed by a vector between the selected endpoints. In this example the vector originates at the center of source #12 in the plaque and is directed towards an inner scleral point opposite the center of the plaque. Ray tracing enables Plaque Simulator to estimate the dosimetric effects of inhomogeneities such as lens, sclera and substitution of vitreous humor with Si oil whose densities and effective atomic numbers differ, perhaps significantly, from those of water. Radiation attenuation at I-125 and Pd-103 energies results primarily from photoeleric interactions which are more affected by these atomic properties than, for example, attenuation resulting from Compton scatter.

Note: in the provided example, ray tracing considers the 1.475 mm of silicone Silastic that the ray traverses within the COMS plaque's carrier to be water equivalent because attenuation owing to that segment of the path is handled by a different calculation factor that has been used by Plaque Simulator going back to the 1990s versions which already accounts for Silastic differences from water. The curent ray tracing is basically an extension of that earier ray tracing that can now be applied to the entire eye without noticably slowing the 3D calculations because computers are now so much faster and support far more RAM to maintain the voxel model than they were in 1990. The default dimensions of a voxel are 0.4 x 0.4 x 0.4 mm but you may optionally decrease that to 0.1 x 0.1 x 0.1 mm voxels via a preferences setting if you have sufficient RAM and need to support the 0.1 mm resolution model. Each voxel uses one byte to encode its tissue type.

You can render the ray traced vector selected in the Ray Tracing window in the 3D Setup window by enabling the Show 3D checkbox control.