Room: Exhibit Hall | Forum 3
Purpose: Clinical electron treatments are typically calculated assuming a flat patient surface that is orthogonal to the radiation beam (en-face). Although fast and convenient, these assumptions can introduce significant dose error for sites that have large curvature. Here, a handheld 3D camera was used to quickly and accurately capture the patient surface. This 3D surface improves dose accuracy of electron treatment plans with minimal additional time, cost, and zero additional radiation dose. The 3D camera scan can also be used create 3D printable bolus, and correct the body surface.
Methods: To validate the accuracy of the 3D camera captured surface, the point cloud of the camera-generated surface model was compared to that of CT-generated surface model. Four clinical plans were calculated with full CT scans (fullCT), 3D camera captured body surfaces with the body overridden to water (3Dwater), as well as calculated en-face on a flat phantom. CT-less 3D surfaces were obtained using an intel D415 stereo depth camera. Scans were converted into CT structures using 3Dslicer (https://www.slicer.org/), and compared using cloud compare (https://www.danielgm.net/cc/).
Results: The 3D camera-generated surface and CT-generated surface point clouds were measured to have a standard deviation of 0.94 mm, with 85% of the points within 2mm. The hotspots of 3Dwater and fullCT calculations agreed within 2.3%, which is significantly improved over the ~8% hotspot errors on the flat phantom. The Monitor units required for 3DWater calculations to cover 95% of the PTV to 100% of the prescribed dose, matched those for fullCT within 1.5%. An exception is a breast plan, where overriding to adipose tissue instead of water, was required to reach agreement within 2%.
Conclusion: Electron beam radiation therapy is highly sensitive to the surface contour. Depth camera surface maps improve dose accuracy of electron treatment plans with low cost, and without ionizing radiation.