Author: Ashish Binjola, Raj Kishore Bisht, Natanasabapathi Gopishankar, Pratik Kumar, Daya Nand Kishore Sharma, Sukhvir Kishore Singh, Subramani Vellaiyan 👨🔬
Affiliation: Medical Physics Unit, All India Institute of Medical Sciences, All India Institute of Medical Sciences, Department of Radiological Safety, Institute of Nuclear Medicine and Allied Sciences, Department of Radiation Oncology, All India Institute of Medical Sciences 🌍
Purpose: Additive manufacturing is increasingly being explored to create dosimetry phantoms. Commercial anthropomorphic phantoms represent an average patient and lack anatomical variations due to obesity, disease-specific or post-operative changes and also have limited predefined fixed dosimetric slots. We applied material extrusion 3D printing which offers a cost-effective method to create customized patient-specific phantoms for dosimetry. As hypofractionated radiation therapy becomes more common, personalized dosimetry is crucial for the accurate dosimetry of the prescribed dose.The aim of this study is the evaluation of radiological properties of PLA composites and fabrication of a personalized dosimetry phantom.
Methods: Multiple cuboids measuring 2 x 2 x 3 cm were 3D printed with varying infill percentages with two Polylactic Acid (PLA) composite filaments: PLA Pro+ and PLA Iron-filled, utilizing a Creality Ender-3 S1 Pro material extrusion-based 3D printer. These blocks were scanned using Dual-Energy Computed Tomography to assess their radiological properties. The evaluation focused on parameters like effective atomic number, electron density, and Hounsfield Units (HU). The results were compared with data from the ICRU Report 44 and with patient computed tomography data to determine the blocks' suitability for mimicking human tissue characteristics.
A personalized head phantom was printed by using the most appropriate infill percentages of these two filaments using anonymized DICOM CT data with 3DSlicer software in which segmentation was done and STL files were prepared for 3D printing.
Results: 84-86 % infill of PLA pro+ closely matches different brain soft tissues in terms of mean electron density (1.010-1.042) and mean HU values (30-42) with an effective atomic number of 7.6. 85% infill of PLA iron-filled closely matches the skull bone with a mean HU value of 890, mean electron density of 1.54, and effective atomic number of 14.5.
Conclusion: PLA composites with material-extrusion can successfully be used for creating personalized dosimetry phantoms.