Use of 3D Printing Technology to Improve Lead Shield Fabrication for Electron Therapy of the Face.

Superficial lesions of the face are often treated with an electron beam and surface collimation utilizing a conformal lead shield with an opening around the region of treatment (ROT). To fabricate the lead shield, an imprint of the patient face is needed. Historically, this was achieved using a laborious and time-consuming process that involved a gypsum imprinted model (GIM) of the patient topography. We propose utilization of 3-dimentional (3D) printing technology to create a 3-dimensional printed custom model (3D-PCM) of the patient facial topography as a more accurate and more efficient alternative to GIM. GIM and 3D-PCM were generated for three patients requiring en face electron therapy of the nose. The models for both methods were then CT-scanned and fused rigidly to the CT of the patient. The accuracy of the models was compared with the CT image of the patient via visual inspection and the Sørensen-Dice similarity coefficient (DSC). The efficiency of the two methods was evaluated by the average time needed to complete each process based on user-reported experience. The average DSC between the patient and GIM is 0.95336 (standard deviation (SD) = 0.0099479), while the average DSC of the patient and 3D-PCM is 0.97886 (SD = 0.0037441). With respect to efficiency, the average time to fabricate and dry GIM is 54.5 hours with hands-on time of 2.5 hours, while generation of 3D-PCM takes about 6.5 hours, with hands on time of approximately 2.5 hours. 3D-PCMs based on CT scan images are found to be an excellent substitute for GIMs by exhibiting a higher degree of fidelity with patient's anatomy, requiring significantly less time to complete, being less labor intensive, and allowing for greater patient comfort. The disadvantage of exposing the patient to radiation associated with the CT scan image acquisition for designing a 3D-PCM could be eliminated by employing 3D-camera scanning technology.