Room: Exhibit Hall | Forum 7
Purpose: To introduce a reliable method for evaluating the dosimetry discrepancy between human tissue and 3D printed materials(3DP-Ms) in diagnostic and treatment radiation, including external photon, electron and proton beams. And the results of materials wildly used in the current market are reported. A GUI program was developed in MATLAB to optimize the composition of 3D printed dose verification QA phantom for the virtue of promising multi-material 4D printing technology.
Methods: 20 materials intended for several printing techniques (PLA,FDM,SLA)were selected from different vendors. For an accurate density measurement, the volume of printed materials was measured by gas pycnometer. Both Element Analysis and EMS-EDS were used to estimate the major element mass fraction of 3D printing materials while the same data of tissue is from the ICRU44 report. A large variety of basic data of radiation(attenuation coefficient, energy absorption coefficient, stopping power)obtained from NIST and recalculated as spectrum weighted average was set as the evaluation index. The typical spectrum is 6MV photon spectrum of Varian Linac IX obtained from IAEA and 150keV CT spectrum simulated from SpectrA3.0. The optimization algorithm is simply an implementation of simulated annealing.
Results: Most of the human tissues has the corresponding equivalent 3DP-Ms whose discrepancies are within 1%, except for cortical bone(1.9g/cmÂ³) and lung(0.26g/cmÂ³).The common 3DP-Ms ABS(1.09g/cmÂ³) and PLA(1.29g/cmÂ³) have discrepancies more than 1% with average tissue(1.6% and 3.5% respectively).The optimization process can reduce the difference to below 0.5%. The 3DP-M varies in density and elemental components from distinguishing vendors, which is worth noticing.
Conclusion: Currently some 3DP-Ms are qualified to be chosen as phantom materials for dose verification. However, for a specific 3DP-M, more investigations are still needed before making phantoms due to the unstable material qualities.