Commissioning Measurements of Flattening Filter and Flattening Filter Free Photon Beams Using a TrueBeam Stx® Linear Accelerator

Document Type : Original Paper


1 Laboratory of Sciences and Health Technologies, High Institute of Health Sciences, Univ Hassan 1 B.P 555, 26000, Settat, Morocco & Department of Radiation Oncology, Sheikh Khalifa International University Hospital BP 82403 Casablanca, Morocco.

2 Laboratory of Sciences and Health Technologies, High Institute of Health Sciences, Univ Hassan 1 B.P 555, 26000, Settat, Morocco

3 Laboratory of Analysis of Systemes and Information Processing, Univ Hassan 1, FST, B.P 577, 26000, Settat, Morocco.


Introduction: TrueBeam STx® latest generation linear accelerators (linacs) were installed at Sheikh Khalifa International University Hospital Casablanca, Morocco, this study aimed to present and analyse the dosimetric characteristics obtained during the commissioning.
Material and Methods: Dosimetric parameters, including percentage depth dose, profiles, output factor, multileaf collimator (MLC) transmission, and dosimetric leaf gaps (DLG) factors were systematically measured for commissioning. Moreover, six photons beams (i.e., X6MV, X6FFFMV, X10MV, X10FFFMV, X15MV, and X18MV) were examined in this study, and a comparison was made between flattening filter (FF) and flattening filter free (FFF) beams.
Results: According to the results, the FF and FFF beams symmetry and flatness were in the tolerance intervals. The unflattness values were estimated at 1.1% and 1.2% for X6FFFMV and X10FFFMV, respectively. Furthermore, tissue phantom ratio(20/10)(TPR) values of the FF beams were X6MV, 0.664; X10MV, 0.738; X15MV, 0.761; and X18MV, 0.778, and the TPR (20/10) values of the FFF beams included 0.632 and 0.703 for 6FFFMV and 10FFFMV, respectively. The results also revealed that the output factor values increased with field size, the surface dose decreased with increasing energy, and the FFF obtained lower mean energy. The MLC transmissions factors were 0.0121, 0.0103, 0.0136, 0.0122, 0.0133,  and 0.0121 for X6, X6FFF, X10, X10FFF, X15, and X18, respectively; additionally, the DLG factors were obtained at 0.32, 0.26, 0.41, 0.37, 0.42, and 0.38 mm for X6, X6FFF, X10, X10FFF, X15, and X18, respectively.
Conclusion: Photon beams reference dosimetric characteristics were successfully matched with the international recommendations and vendor technical specifications.


Main Subjects

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Volume 18, Issue 1
January and February 2021
Pages 49-62
  • Receive Date: 21 January 2019
  • Revise Date: 06 September 2019
  • Accept Date: 26 November 2019