Design and additive manufacture of patient-specific head phantom for radiotherapy

• A novel custom 3D printing material was developed specifically to replicate the radiodensity characteristics of bone. • A modular design to fabricate the head phantom, enabling efficient production while preserving anatomical specificity to the individual patient. • A patient-specific head model was fabricated using multi-material 3D printing, with segmented tissue regions defined based on HU value ranges. • This work highlights the effectiveness of the custom material and 3D printing process in replicating intended bone radiodensity. 3D printing has extensive potential in medical fields in creating prototypes for treatment planning and in this study, the materials and design of a modular head phantom for dosimetry quality assurance in radiotherapy of cancer treatment were described. Till now, the challenge in medical phantoms lies in their ability to accurately represent the anatomical and radiodensity heterogeneity of actual human tissues using representative synthetic materials and topology. Here, polylactic acid was employed for soft tissue representation, while a new custom material mix of Acrylonitrile Butadiene Styrene and bismuth was developed to replicate the higher Hounsfield Unit values characteristic of bone. Appropriate 3D printing infill densities derived from their respective linear regressions were implemented to achieve specific target radiodensities. To facilitate the efficient assembly, structural and anatomical fidelity, the head phantom was printed in 39 consecutive sections, post-processed and scanned using computed tomography (CT). Validation confirmed the success of the fabrication process, achieving both anatomical accuracy and radiodensity consistency, even in regions with complex geometries and high heterogeneity. This study marks a significant step in advancing the use of 3D printing and modularity design that can be patient-specific in developing cancer treatment processes and contributes to safer and more effective radiotherapy.