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

  1. Sahani G, Sharma SD, Sharma PD, Deshpande DD, Negi PS, Sathianarayanan VK , et al. Acceptance criteria for flattening filter-free photon beam from standard medical electron linear accelerator:  AERB task group recommendations, Journal of Medical Physics/Association of Medical Physics of India. 2014 Oct;39(4) 206. 
  2. Chang Z, Wu Q, Adamson J, Ren L, Bowsher J, Yan H, et al. Commissioning and dosimetric characteristics of TrueBeam system: composite data of three TrueBeam machines, Medical physics. 2012 Nov;39(11):6981-7018.
  3. Hrbacek J, Lang S, Klöck S, Commissioning of photon beams of a flattening filter-free linear accelerator and the accuracy of beam modeling using an anisotropic analytical algorithm, International Journal of Radiation Oncology* Biology* Physics. 2011 Jul 15;80(4):1228-37.
  4. Shende R, Gupta G, Patel G, Kumar S. Commissioning of TrueBeam TM Medical Linear Accelerator : Quantitative and Qualitative Dosimetric Analysis and Comparison of Flattening Filter (FF) and Flattening Filter Free (FFF) Beam. International Journal of Medical Physics, Clinical Engineering and Radiation Oncology.2016;5(01):51.
  5. Beyera GP. Commissioning measurements for photon beam data on three TrueBeam linear accelerators, and comparison with Trilogy and Clinac 2100 linear accelerators. Journal of  applied clinical medical physics. 2013 Jan; 14(1):273–88.
  6. Fogliata A, Garcia R, Knöös T, Nicolini G, Clivio A, Vanetti E, et al. Definition of parameters for quality assurance of flattening filter free (FFF) photon beams in radiation therapy, Medical physics. 2012 Oct; 39(10): 6455-64.
  7. Vassiliev ON, Titt U, Pönisch F, Kry SF, Mohan R, Gillin MT. Dosimetric properties of photon beams from a flattening filter free clinical accelerator. Physics in Medicine & Biology. 2006 Mar 22;51(7):1907.
  8. Kragl G, af Wetterstedt S, Knäusl B, Lind M, McCavana P, Knöös T, et al. Dosimetric characteristics of 6 and 10 MV unflattened photon beams. Radiotherapy and Oncology. 2009 Oct 1;93(1):141-6.
  9. Yan Y, Yadav P, Bassetti M, Du K, Saenz D, Harari P, et al. Dosimetric differences in flattened and flattening filter-free beam treatment plans. Journal of medical physics/Association of Medical Physicists of India. 2016 Apr;41(2):92.
  10. Wang Y, Khan MK, Ting JY, Easterling SB. Surface dose investigation of the flattening filter-free photon beams. International Journal of Radiation Oncology* Biology* Physics. 2012 Jun 1;83(2):e281-5.
  11. Tsiamas P, Seco J, Han Z, Bhagwat M, Maddox J, Kappas C, et al. A modification of flattening filter free linac for IMRT. Medical physics. 2011 May;38(5):2342-52.
  12. Titt U, Vassiliev ON, Poenisch F, Dong L, Liu H, Mohan R. A flattening filter free photon treatment concept evaluation with Monte Carlo. Medical physics. 2006 Jun;33(6Part1):1595-602.
  13. Varian Medical Systems, U. States, TrueBeam / Administrators Guide. 2015.
  14.  Varian Medical Systems, Eclipse 10 Inverse Planning Administration and Physics. 2011; 1–721.
  15. Klein EE, Hanley J, Bayouth J, Yin FF, Simon W, Dresser S, et al. Task Group 142 report: Quality assurance of medical acceleratorsa. Medical physics. 2009 Sep 1;36(9Part1):4197-212.
  16. Das IJ, Cheng CW, Watts RJ, Ahnesjö A, Gibbons J, Li XA, et al. Accelerator beam data commissioning equipment and procedures: report of the TG‐106 of the Therapy Physics Committee of the AAPM. Medical physics. 2008 Sep;35(9):4186-215.
  17. Almond PR, Biggs PJ, Coursey BM, Hanson WF, Huq MS, Nath R, et al. AAPM's TG‐51 protocol for clinical reference dosimetry of high‐energy photon and electron beams. Medical physics. 1999 Sep 1;26(9):1847-70.
  18. Musolino SV. Absorbed Dose Determination in External Beam Radiotherapy: An International Code of Practice for Dosimetry Based on Standards of Absorbed Dose to Water; Technical Reports Series No. 398. Health Physics. 2001 Nov 1;81(5):592-3.
  19. Kielar KN, Mok E, Hsu A, Wang L, Luxton G. Verification of dosimetric accuracy on the TrueBeam STx: rounded leaf effect of the high definition MLC. Medical physics. 2012 Oct;39(10):6360-71.
  20. Gluhcheva Y, Dimitrova TL, Dukova R, Zheleva N, Koleva I, Encheva E. Dosimetry acceptance test of linear accelerator Varian Clinac iX. scanning. 2015 Jan 1;900:2.
  21. Varian Medical Systems. Eclipse Algorithms Reference Guide Eclipse. 2011; 1–368. doi:p/n B503486R01B.
  22. Khan FM. Physics of Radiation Therapy Third Edition, J. Am. Med. Assoc. 2003; 1138.
  23. Varadharajan E, Ramasubramanian V. Commissioning and Acceptance Testing of the existing linear accelerator upgraded to volumetric modulated arc therapy. Reports of Practical Oncology & Radiotherapy. 2013 Sep 1;18(5):286-97.
  24. Szpala S, Cao F, Kohli K. On using the dosimetric leaf gap to model the rounded leaf ends in VMAT/RapidArc plans. Journal of applied clinical medical physics. 2014 Mar;15(2):67-84.
  25. Heath E, Seuntjens J, Carlo M, Georg D, Julia F, Briot E. Experimental characterization of the dosimetric leaf gap. 1976.
  26. Balasingh ST, Singh IR, Rafic KM, Babu SE, Ravindran BP. Determination of dosimetric leaf gap using amorphous silicon electronic portal imaging device and its influence on intensity modulated radiotherapy dose delivery. Journal of Medical Physics/Association of Medical Physicists of India. 2015 Jul;40(3):129.



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
  • First Publish Date: 01 January 2021