Impact of 6 MV & 10 MV Flattened and Flattening Filter Free Beams in Whole Brain Radiotherapy: A Treatment Planning Study

Document Type : Original Paper


1 1. Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, Rohini, New Delhi, India 2. School of Advanced Sciences, VIT University, Vellore, Tamil Nadu, India

2 School of Advanced Sciences, VIT University, Vellore, Tamil Nadu, India


Introduction:To study the impact of 6 MV and 10 MV flattened beam (FB) and flattening filter free (FFF) beam in whole brain radiotherapy (WBRT) by using volumetric modulated arc therapy (VMAT).
Material and Methods: Twenty WBRTpatients were selected randomly. The dose prescription was 30 Gy, which was delivered in ten fractions. The planning target volume (PTV) and organs at risk (OARs) were contoured. Four VMAT plans, including 6 MV FB, 6 MV FFF, 10 MV FB, and 10 MV FFF beam plans, were generated.
Results: The 6MV FB and FFF beam plans were statistically significant (p <0.05) in terms of the dose received by 98% of the PTV (D98%) (26.86 Gy vs. 27.31 Gy, P=0.006), the dose received by 95% of the PTV (D95%) (28.28 Gy vs. 28.52 Gy, P=0.038), 107% isodose (V107%) of the PTV (2.43% vs. 3.74%, P=0.001), D100% of the hippocampus (9.31 Gy vs. 9.16 Gy, P=0.009), and the Dmean scalp (16.7 Gy vs. 16.8 Gy, p=0.035). The 10 MV FB and FFF beam plans showed significant differences in the conformity index (0.9 vs. 0.85, P=0.01), V107% of the PTV (1.68% vs. 4.54%, P=0.001), D100% (10.08 Gy vs. 9.81 Gy, P=0.036), and Dmean of the hippocampus (12.78 Gy vs. 12.57 Gy, P=0.018). The 6 MV and 10 MV FFF beams showed homogeneous conformal plans, which required 18-19% more MUs, compared to the FB plans.
Conclusion: The 6 MV and 10 MV FB and FFFB spared the hippocampus and the scalp with acceptable target coverage in WBRT cases.


Main Subjects

  1. Khuntia D, Brown P, Li J, Mehta MP. Whole‑brain radiotherapy in the management of brain metastasis. J ClinOncol. 2006; 24:1295‑304.
  2. Lautin A: Limbic Brain. New York: Kluwer Academic/Plenum; 2001.
  3. Tofilon PJ, Fike JR: The radioresponse of the central nervous system: a dynamic process. Radiat Res. 2000, 153(4):357–70.
  4. Gondi V, Pugh SL, Tome WA, Caine C, Corn B, Kanner A, et al. Preservation of memory with conformal avoidance of the hippocampus neural stem‑cell compartment during whole‑brain radiotherapy for brain metastases (RTOG 0933): A phase II multi‑institutional trial. J ClinOncol. 2014; 32:3810‑6.
  5. Teoh M, Clark CH, Wood K, Whitaker S, Nisbet A. Volumetric modulated arc therapy: a review of current literature and clinical use in practice. The British journal of radiology. 2011 Nov;84(1007):967-96. DOI: 10.1259/bjr/22373346.
  6. Fippel M, Haryanto F, Dohm O, Nüsslin F, Kriesen S. A virtual photon energy fluence model for Monte Carlo dose calculation. Med Phys. 2003; 30:301 11.
  7. Kry SF, Titt U, Pönisch F, Vassiliev ON, Salehpour M, Gillin M, et al. Reduced neutron production through use of a flattening filter free accelerator. Int J RadiatOncolBiol Phys. 2007; 68:1260 4.
  8. Spruijt KH, Dahele M, Cuijpers JP, Jeulink M, Rietveld D, Slotman BJ, et al. Flattening filter free vs flattened beams for breast irradiation. Int J RadiatOncolBiol Phys. 2013; 85: 506–13. DOI: 10.1016/j. ijrobp.2012.03.040 PMID: 22672750.
  9. Tamilarasu S, Saminathan M, Sharma SK. Treatment Planning With Unflattened as Compared to Flattened Beams for Bilateral Carcinoma of the Breast. Asian Pacific journal of cancer prevention: APJCP. 2017;18(5):1377. DOI: 10.22034/APJCP.2017.18.5.1377.
  10. Hrbacek J, Lang S, Graydon SN, Klock S, Riesterer O. Dosimetric comparison of flattened and flattening filterm free beams for stereotactic ablative radiotherapy of stage I non-small cell lung cancer. Med Phys. 2014; 41: 031709. DOI: 10.1118/1.4866231 PMID: 24593713.
  11. Tamilarasu S, Saminathan M, Sharma SK, Pahuja A, Dewan A. Comparative Evaluation of a 6MV Flattened Beam and a Flattening Filter Free Beam for Carcinoma of Cervix–IMRT Planning Study. Asian Pacific journal of cancer prevention: APJCP. 2018;19(3):639.
  12. Vol I. Prescribing, recording, and reporting photon-beam intensity-modulated radiation therapy (IMRT): contents. J ICRU. 2010;10.
  13. Lechner W, Kragl G, Georg D. Evaluation of treatment plan quality of IMRT and VMAT with and without flattening filter using Pareto optimal fronts. RadiotherOncol. 2013; 109: 437–41. DOI: 10.1016/j.radonc.2013.09.020.
  14. Siglin J, Champ CE, Vakhnenko Y, Witek ME, Peng C, Zaorsky NG, et al. Optimizing patient positioning for intensity modulated radiation therapy in hippocampal-sparing whole brain radiation therapy. Practical radiation oncology. 2014 Nov 1;4(6):378-83. DOI:10.1016/j.prro.2013.11.008.
  15. Kim KS, Seo SJ, Lee J, Seok JY, Hong JW, Chung JB, et al. Inclined head position improves dose distribution during hippocampal-sparing whole brain radiotherapy using VMAT. Strahlentherapie und Onkologie. 2016 Jul;192(7):473-80. DOI: 10.1007/s00066-016-0973-0.
  16. Gondi V, Hermann BP, Mehta MP, Tome WA. Hippocampal dosimetry predicts neurocognitive function impairment after fractionated stereotactic radiotherapy for benign or low-grade adult brain tumors. Int J RadiatOncolBiol Phys. 2013; 85:348–54.
  17. Olsen E. Anagen hair loss: Radiation. In: Olsen EA, editor. Disorders of hair growth: Diagnosis and treatment. New York: McGraw Hill. 1994; 225–6.
  18. Valentin J. Avoidance of radiation injuries from medical interventional procedures. Ann ICRP. 2000; 30:7–67.
  19. Kyoizumi S, Suzuki T, Teraoka S, Seyama T. Radiation Sensitivity of Human Hair Follicles in SCID- hu Mice Radiation Research. 1998; 149:11–8. DOI: 10.2307/3579676.
  20. Potten CS, Burt PA, Roberts SA, Deshpande NA, Williams PC. Changes in the Cellularity of the Cortex of Human Hairs as an Indicator of Radiation Exposure Radiation and Environmental Biophysics Impact Factor. 1996; 35:121–5. DOI: 10.1007/BF02434035.
  21. Hamilton CS, Potten CS, Denham JW, O’Brien PC, Kron T. Response of Human Hair Cortical Cells to Fractionated Radiotherapy Radiotherapy and Oncology. 1997; 43:289–92. DOI: 10.1016/S0167-8140(97)00059-5.
  22. Krayenbuehl J, Di Martino M, Guckenberger M, Andratschke N. Improved plan quality with automated radiotherapy planning for whole brain with hippocampus sparing: A comparison to the RTOG 0933 trial. RadiatOncol. 2017; 12:161.
  23. 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. 
  24. Kao J, Darakchiev B, Conboy L, Ogurek S, Sharma N, Ren X, et al. Tumor directed, scalp sparing intensity modulated whole brain radiotherapy for brain metastases. Technology in cancer research & treatment. 2015 Oct;14(5):547-55.
  25. Sood S, Pokhrel D, McClinton C, Lominska C, Badkul R, Jiang H, et al. Volumetric-modulated arc therapy (VMAT) for whole brain radiotherapy: not only for hippocampal sparing, but also for reduction of dose to organs at risk. Medical Dosimetry. 2017 Dec 1;42(4):375-83. DOI: 10.1016/j.meddos.2017.07.005.
  26. Ghia A, Tomé WA, Thomas S, Cannon G, Khuntia D, Kuo JS, et al. Distribution of brain metastases in relation to the hippocampus: implications for neurocognitive functional preservation. International Journal of Radiation Oncology* Biology* Physics. 2007 Jul 15;68(4):971-7. 
  27. Gondi V, Tome WA, Marsh J, Struck A, Ghia A, Turian JV, et al. Estimated risk of perihippocampal disease progression after hippocampal avoidance during whole-brain radiotherapy: Safety profile for RTOG 0933. RadiotherOncol. 2010; 95:327–31.
  28. Kry SF, Bednarz B, Howell RM, Dauer L, Followill D, Klein E, Paganetti H, et al. AAPM TG 158: measurement and calculation of doses outside the treated volume from external‐beam radiation therapy. Medical physics. 2017 Oct 1;44(10):e391-429. 
  29. Fogliata A, Bergström S, Cafaro I, Clivio A, Cozzi L, et al. Cranio-spinal irradiation with volumetric modulated arc therapy: A multi-institutional treatment experience. Radiotherapy and Oncol. 2011; 99: 79–85.
  30. Diallo I, Haddy N, Adjadj E, Samand A, Quiniou E, Chavaudra J, et al. Frequency distribution of second solid cancer locations in relation to the irradiated volume among 115 patients treated for childhood cancer. International Journal of Radiation Oncology* Biology* Physics. 2009 Jul 1;74(3):876-83. 
  31. Hall EJ, Wuu CS. Radiation-induced second cancers: the impact of 3D-CRT and IMRT. Int J RadiatOncolBiol Phys. 2003; 56 (1):83–8.
  32. Kragl G., Baier F., Lutz S. Flattening filter free beams in SBRT and IMRT: dosimetric assessment of peripheral doses. Z Med Phys. 2011;21(May (2)):91–101.
  33. Kry SF, Vassiliev ON, Mohan R. Out-of-field photon dose following removal of the flattening filter from a medical accelerator. Phys Med Biol. 2010;55(8):2155–66.
  34. Sohrabi M, Morgan KZ. Neutron dosimetry in high energy X-ray beams of medical accelerators. Phys Med Biol. 1979;24(4):756–66.
  35. Sohrabi M, Hakimi A. Novel 6MV X-ray photoneutron detection and dosimetry of medical accelerators. Phys Med. 2017; 36:103–9.