Development and validation of a 3D-printed dosimetry phantom for paediatric radiology

Radiation dosimetry is essential in the optimisation and justification of medical imaging procedures. However, the complexity of modern imaging equipment often surpasses the capabilities of standard dose calculation software, necessitating the use of commercially available dosimetry phantoms, which are often prohibitively expensive. This study aimed to develop a cost-effective, 3D-printed newborn-equivalent dosimetry phantom for measuring organ and whole-body effective doses. Several Polylactic Acid (PLA)-based filaments were investigated for tissue equivalency through Hounsfield-value analysis via micro-CT (40-70 kVp) and clinical CT (70-140 kVp) measurements. Standard PLA at 93% (ρ = 1.14 g/cm³) and 26% (ρ = 0.41 g/cm³) infill density was selected for soft tissue and lung, respectively, while StoneFil composite PLA (FormFutura) at 81% (ρ = 1.21 g/cm³) infill was chosen for bone. The phantom was modelled on a modified Cristy and Eckerman newborn design, with 21 sections generated using MATLAB and printed on a Bambu Lab X1 Carbon 3D printer. A total of 186 thermoluminescent dosimeter (TLD) capsules were embedded in the phantom, and TLD measurements from whole-body 60 kVp radiographs were compared with Monte Carlo (PCXMC 2.0) simulations for validation. The phantom demonstrated accurate dosimetry for the radiographic exposure, with average organ doses closely matching the simulated exposure, and the effective dose (ICRP 103) within 2% of the simulation. The phantom required 135 h to print, with a material cost of A$165. This study successfully developed and validated a cost-effective dosimetry phantom for paediatric radiography, with the potential to print larger phantoms for older children. Future work will explore the phantom's application in other X-ray imaging modalities.