Design of a 3D Printed Immobilization Device for Radiation Therapy of Experimental Tumors in Mice

Abstract

Transplantable murine tumor models are critical for radiobiological studies of proton and photon radiation, and immobilization devices are essential for accurate tumor (often <1 cm) targeting in these models. We utilized three-dimensional (3D) printing technology to design and produce an immobilization device for this purpose. All procedures were approved by the institutional animal care committee. CT imaging of a C57BL/6 mouse was performed, and the Blender software package was used to generate a surface contour. A clamshell device was designed with a negative impression of the animal surface contour, and a lateral aperture for flank tumors. A brass block was affixed to reduce beam penumbra. The device was printed from polylactic acid polymer using an Ultimaker 2 3D printer and tested on a mouse harboring a subcutaneous flank tumor (EL4 Thymoma). Tumor motion was tracked in the x, y, and z planes using video monitoring over 15 minutes. Animals (n=3) were safely immobilized with no signs of trauma or distress. Minimal tumor movement was observed in the x, y, and z planes. Proton and photon treatment plans were generated using Eclipse software, demonstrating uniform targeting of the tumor with <10% of the prescribed dose delivered to the abdominal or thoracic cavity. We present the rapid and cost-effective design and production of an immobilization device using 3D printing for the treatment of experimental murine tumors with photon or proton beam radiotherapy.