Document Type: Original Research


1 PhD, Department of Nuclear Engineering, Faculty of Mechanical Engineering, Shiraz University, Shiraz, Iran

2 MSc, Department of Nuclear Engineering, Faculty of Mechanical Engineering, Shiraz University, Shiraz, Iran


Background: Recently, multileaf collimators (MLC) have become an important part of any LINAC collimation system because they reduce the treatment planning time and improve the conformity. Important factors that affect MLCs collimation performance are leaves material composition and their thickness.
Objective: In this study, we investigate main dosimetric parameters of a typical MLC including dose in the buildup point, physical penumbra as well as average and end leaf leakages. Effects of the leaves geometry and density on these parameters are evaluated.
Materials and Methods: In this analytical study, calculations were performed by using phase space data for Varian ix just above MLC and BEAMnrc/DOSXYZnrc for SSD=100cm and in a water phantom.
Results: Based on the results, a new MLC with improved dosimetric parameters is proposed. The physical penumbra for proposed MLC is 4.7mm was compared to 5.16 mm for Millennium 120 leaf. Average leakage in our design is reduced to 1.16% compared to 1.73% for Millennium 120 leaf, the end leaf leakage suggested design also reduced to 4.86% compared to 7.26% for Millennium 120 leaf.
Conclusion: The results show that the proposed MLC could improve the dosimetric parameters and conformity of treatment planning.


  1. Khan FM, Gibbons JP. Khan’s the physics of radiation therapy. Philadelphia: Lippincott Williams & Wilkins; 2014.
  2. Kawrakow I, Mainegra-Hing E, Rogers DWO, Tessier F, Walters BRB. The EGSnrc code system: Monte Carlo simulation of electron and photon transport. Canada: NRC; 2001-2015.
  3. Ezzell GA, Galvin JM, Low D, Palta JR, Rosen I, Sharpe MB, et al. Guidance document on delivery, treatment planning, and clinical implementation of IMRT: report of the IMRT Subcommittee of the AAPM Radiation Therapy Committee. Med Phys. 2003;30:2089-115. PubMed PMID: 12945975.
  4. Galvin JM, Smith AR, Lally B. Characterization of a multileaf collimator system. International Journal of Radiation Oncology Biology Physics. 1993;25:181-92.
  5. Cosgrove VP, Jahn U, Pfaender M, Bauer S, Budach V, Wurm RE. Commissioning of a micro multi-leaf collimator and planning system for stereotactic radiosurgery. Radiother Oncol. 1999;50:325-36. PubMed PMID: 10392819.
  6. Woo M, Charland P, Kim B, Nico A. Commissioning, evaluation, quality assurance and clinical application of a virtual micro MLC technique. Med Phys. 2003;30:138-43. PubMed PMID: 12607831.
  7. Heydarian M, Fung B, Laperriere N. SU-FF-T-402: Dosimetric Comparison of Different MLC Systems for IMSRT. Med Phys. 2005;32:2043.
  8. Burmeister J, Sharma P. WE-D-224C-06: Leakage Characteristics of Two Common Multi-Leaf Collimators: Implications for Intensity Modulated Radiotherapy. Med Phys. 2006;33:2250.
  9. Appenzoller L, Perera H, Sullivan P, Hand C, Hasson B. SU-GG-T-277: Dosi Metric Comparison of the New Siemens 160 MLC and the Varian Millennium 120 MLC. Med Phys. 2010;37:3249.
  10. Rogers D, Walters B, Kawrakow I. BEAMnrc users manual. NRC Report PIRS. Canada: NRC; 2009;509:12.
  11. Rogers DWO, Walters B, Kawrakow I. DOSXYZnrc users manual. NRC Report PIRS. Canada: NRC; 2005;794.
  12. Hadad K, Ganapol BD, Hamilton R, Watchman C, editors. Dose verification for accelerated partial breast irradiation. International Conference on Advances in Mathematics, Computational Methods & Reactor Physics; United States, New York; 2009.
  13. Haddad K, Alopoor H. SU-F-T-366: Dosimetric Parameters Enhancement of 120-Leaf Millennium MLC Using EGSnrc and IAEA Phase-Space Data. Med Phys. 2016;43:3547.
  14. Hadad K, Zohrevand M, Faghihi R, Sedighi Pashaki A. Accuracy Evaluation of Oncentra TPS in HDR Brachytherapy of Nasopharynx Cancer Using EGSnrc Monte Carlo Code. J Biomed Phys Eng. 2015;5:25-30. PubMed PMID: 25973408. PubMed PMCID: 4417616.
  15. Hadad K, Saeedi-Moghadam M, Zeinali-Rafsanjani B. Voxel dosimetry: Comparison of MCNPX and DOSXYZnrc Monte Carlo codes in patient specific phantom calculations. Technol Health Care. 2017;25:29-35. PubMed PMID: 27447407.
  16. In: OzRodOnc. Descriptors Of Dose Distribution (Photons): Photon Beam Charts. Available from:
  17. De Oliveira ACH, Vieira JW, Lima FRA. Monte Carlo modeling of multileaf collimators using the code Geant4. Brazilian Journal of Radiation Sciences. 2015;3(1A).
  18. Capote R, Jeraj R, Ma C, Rogers D, Sánchez-Doblado F, Sempau J, et al. Phase-space database for external beam radiotherapy. IAEA, Nucl. Data Sec. Report INDC (NDS)-0484: Vienna, Austria: International Atomic Energy Agency; 2006.
  19. Sharma DS, Dongre PM, Mhatre V, Heigrujam M. Physical and dosimetric characteristic of high-definition multileaf collimator (HDMLC) for SRS and IMRT. J Appl Clin Med Phys. 2011;12:3475. PubMed PMID: 21844860.
  20. IAEA TRS 398. Absorbed dose determination in external beam radiotherapy: An International Code of Practice for Dosimetry based on standards of absorbed dose to water. Vienna, Austria: International Atomic Energy Agency; 2006.
  21. Welsch G, Boyer R, Collings EW. Materials properties handbook: titanium alloys. United Stateds of America: ASM international; 1993.