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Comparison of Single and Dual Material 3D Printed Patient-Specific Radiotherapy Phantoms

D Craft

DF Craft*, M Peters , G Baltz , RM Howell , UT MD Anderson Cancer Center, Houston, TX


SU-I-GPD-T-218 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: 3D printing technology can fabricate patient-specific phantoms rapidly and inexpensively. However, most 3D printers are limited to either one or two materials at a time, and using two materials often comes with a tradeoff in print quality. In this study we printed a single material and a dual-material phantom based on the same patient to compare these techniques.

Methods: Both phantoms were designed using CT data from a patient treated at our institution. The single material phantom (1) was designed by converting the CT into a 3D model and slicing it into 11 sagittal slices. The dual-material phantom (2) was created by segmenting both a soft tissue and bone model from the patient, then converting both to 3D models, and slicing into 11 slices. Phantom 2 also had immobilization rod holes and holes for TLD designed into it. Phantom 1 used PLA with low density regions like the lungs left open. Phantom 2 used PLA and ABS for the bone soft tissue models, respectively.

Results: Both phantoms printed accurately, with volumetric errors <2% between the designed models and actual printed slices. Phantom 2’s PLA oozed and mixed slightly with the ABS, resulting in less distinct bone regions than hoped. Phantom 1 had an average HU of 133.99±12.48, and phantom 2 had an average soft tissue and bone HU of -125.26±12.27 and -11.67±50.06 respectively. The immobilization and TLD holes for phantom 2 printed accurately, with TLD fitting perfectly.

Conclusion: Phantom 1 was simpler to design and print, but is homogenous and has a high HU. Phantom 2 was more complex to design and print, but offers some heterogeneity, and had better soft tissue HU matching. More work is needed to reduce material oozing in dual-material prints, but multi-material patient specific phantoms are possible and promising.

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