Commissioning Tests of Radixact Synchrony Using Patient-Specific 3D-Printed Lung Phantom Inserts

The use of Radixact Synchrony real-time adaptive motion management for lung cancer patients depends on automated detection and delineation of the tumor from surrounding tissues, in addition to the use of surrogate tracking. This functionality should ideally be tested during commissioning using quality assurance phantoms prior to clinical use. However, most dynamic thorax phantoms feature simplistic lung tumors-easily delineated spheres surrounded by low-density tissue. The aim of this project was to design and fabricate more realistic phantoms for Synchrony testing. A selection of eight lung cancer patient CT datasets was retrospectively selected, encompassing variations in size, edge definition, soft tissue attachment, and surrounding fibrosis. Tissues were segmented within 3D Slicer to produce multiple 3D models (in STL format), each corresponding to a range of CT number values. These 3D models were printed at different densities within a larger lung insert that could be inserted into a CIRS Dynamic Thorax Phantom. Mock treatment plans were prepared for these treatments. Replacement lung rods containing more realistic tumors were printed and successfully used for Radixact Synchrony commissioning tests. Results found that across all 3D-printed lung inserts, Radixact Synchrony was able to track motion within 1 mm in both the superior-inferior and left-right directions for a typical lung motion. During erratic breathing motions in the high-frequency breathing trace, Radixact Synchrony was able to approximately pause treatment when the correlation model aged. 3D printing provides an easy and affordable way to extend the functionality of existing phantoms and to assist in the commissioning of novel technologies such as Radixact Synchrony.