ESTRO 2021 Abstract Book

S1303

ESTRO 2021

[1] S. M. Jafari et al., ‘Low-cost commercial glass beads as dosimeters in radiotherapy’, Radiation Physics and Chemistry, vol. 97, pp. 95–101, Apr. 2014, doi: 10.1016/j.radphyschem.2013.11.007.

PO-1578 Low-cost 3D-printed phantom for in-air calibration of high-dose rate 192Ir brachytherapy source F. Biltekin 1 , M. Gultekin 1 , H.F. Akyol 1 , F. Yildiz 1 1 Hacettepe University, Faculty of Medicine, Department of Radiation Oncology, Ankara, Turkey Purpose or Objective To assess the accuracy and feasibility of the novel 3D-printed phantom setup for in-air calibration of 192Ir high-dose rate (HDR) brachytherapy sources in routine clinical practice. Materials and Methods Low-cost brachytherapy phantom was modeled in SketchUp Pro 2017 modeling software and printed out from a MakerBot Replicator Z18 3D-printer. Two sets of measurements were performed in a Varian GammaMed iX Plus HDR brachytherapy. In the first step, the source strength was measured at reference in-air measurement conditions defined in IAEA TECDOC 1079 and 1274 report with specially designed setup using 0.6 cc ionization chamber. Measurements were repeated for two different source strengths (1 st source strength: 10.592 Ci and 2 nd source strength: 3.660 Ci). In the second step, to validate the feasibility of the novel phantom, measurement was performed with 3D-printed phantom as illustrated in Figure 1. Then, measured source strength with 3D-printed phantom setup was compared with both reference in-air measurement defined in the first step and source strength quoted by the manufacturer.

Results The source strengths measured with 3D-printed phantom setup were found as 10.806 Ci (quoted by the manufacturer: 10.592 Ci) and 3.672 Ci (quoted by the manufacturer: 3.660 Ci). Measured source strength were in good agreement (< 2.02%,) with the manufacturer stated values. Additionally, source strength values with respect to the reference measurement setup were compatible with in 0.7%. Conclusion The use of low-cost 3D-printed phatom was found feasible for in-air calibration of 192Ir HDR brachytherapy sources in routine clinical practice. Nevertheless, 3D-printed phantom need to be commisioned for defining optimal dosimetric and physical characteristics depending on printing parameters like printing filament materials, infill percentage, infill pattern,printing direction etc.

PO-1579 Dosimetric effects of small fields and air gaps when using 3D printed bolus E. Spelleken 1,3 , J. Hellyer 2 , S. Crowe 3,4,5 , T. Kairn 3,4,5

1 GenesisCare, Rockhampton, Rockhampton, Australia; 2 GenesisCare, Macquarie University Hospital, Sydney, Australia; 3 University of Queensland, School of Information Technology and Electrical Engineering, Brisbane, Australia; 4 Royal Brisbane and Women's Hospital, Cancer Care Services, Brisbane, Australia; 5 Metro North