ESTRO 2023 - Abstract Book

S1591

Digital Posters

ESTRO 2023

Conclusion Accounting for thermal effects voxelwise allows to control both EQDRT level and homogeneity during RT optimization, which is not possible for standard planning. A risk of adjustments during treatment is that EQDRT objectives for GTV coverage are no longer met. This can be avoided by having alternative RT plans optimized with HT plans taking into account realistic adjustment scenarios. OARs’ DVH shape can be kept similar to standard planning, while D0.1% can increase up to 3 Gy.

PO-1852 Novel Multi Jet Fusion 3D Printed Immobilizers Allowing Significant Reduction of Skin Dose

J. Robar 1 , B. Kammerzell 2 , K. Hulick 2 , P. Kaiser 2 , C. Young 2 , V. Verzwyvelt 2 , X. Cheng 2 , M. Shepherd 2 , R. Orbovic 3 , S. Fedullo 3 , C. Majcher 4 , S. DiMarco 4 , J. Stasiak 5 1 Nova Scotia Health / Dalhousie University, Medical Physics, Halifax, Canada; 2 HP, Additive Manufacturing, Corvallis, USA; 3 Adaptiiv Medical, Medical Physics, Halifax, Canada; 4 Adaptiiv Medical, Software Engineering, Halifax, Canada; 5 HP, HP Labs, Corvallis, USA Purpose or Objective Standard immobilizers used in radiation oncology require manual forming of hot thermoplastic over the patient surface. Aside from being an anxiety-causing experience for many patients, the quality of the device, and in turn its immobilizing performance, will be subject to the skill of the practitioner. In this work we present a new development: Multi Jet Fusion (MJF) 3D printed immobilizers. With the aim of minimizing skin dose and toxicity, we examine the surface dose characteristics for various MJF material options, with comparison to common fused deposition modeling (FDM) materials and standard thermoplastic mesh. We present a novel honeycomb metamaterial design to satisfy the goals of material stiffness and minimal radiological path length, and demonstrate skin dose reduction afforded by these designs. Finally, we show the first cranial and head-and-neck immobilizer prototypes and quantify their spatial fidelity. Materials and Methods Three types of MJF-printable PA12 materials were compared to common FDM-printed polylactic acid (PLA) as well as PLA with the addition of hollow glass microspheres (HGMs) to lower density. Percent depth dose over the superficial 15 mm were perfomed using an Advanced Markus chamber, and compared to solid, stretched and unstretched perforated thermoplastic. A metamaterial honeycomb design was developed, and the dependencies of surface dose, as measured using calibrated radiochromic dosimetry, on hexagonal cell height, thickness and face thickness were measured. Finally, full adult and paediatric cranial immobilizers, as well as extended head-and-neck immobilizers, were designed and fabricated