Document Type: Original Research

Authors

1 Department of Medical Physics, Tehran University of Medical Sciences, Tehran, Iran

2 Radiation biology research center & medical Physics department, faculty of medicine, Iran University of Medical Sciences, Tehran, Iran

3 Department of Medical Physics, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran

4 Department of Clinic for Radiotherapy and RadioOncology, Medical Faculty Mannheim of the University of Heidelberg, Heidelberg, Germany

5 Department of Medical Physics, Iran University of Medical Sciences, Tehran, Iran

Abstract

Background: Before treatment planning and dose delivery, quality assurance of multi-leaf collimator (MLC) has an important role in intensity-modulated radiation therapy (IMRT) due to the creation of multiple segments from optimization process.
Objective: The purpose of this study is to assess the quality control of MLC leaves using EBT3 Gafchromic films.
Material and Methods: Leaf Position accuracy and leaf gap reproducibility were checked with Garden fence test. The garden fence test consists of 5 thin bands A) 0.2 Cm width spaced at 2 Cm intervals and B) 1 Cm width spaced at 1 Cm intervals. Each leaf accuracy was analyzed with measuring the full-width half-maximum (FWHM). Maximum and average leaf transmission were measured with gafchromic EBT3 films from Ashland for both 6 MV and 18 MV beams.
Results: Leaf positions were found to be in a range between 1.78 – 2.53 mm, instead of nominal 2 mm for the test A and between 9.09 – 10.36 mm, instead of nominal 10 mm for the test B. The Average radiation transmission of the MLC was noted 1.79% and 1.98% of the open 10x10 Cm2 field at isocenter for 6 MV and 18 MV beams, respectively. Maximum radiation transmission was noted 4.1% and 4.4% for 6 MV and 18 MV beams, respectively.
Conclusion: In this study, application of gafchromic EBT3 films for the quality assurance of Euromechanics multileaf collimator was studied. Our results showed that the average leaf leakage and positional accuracy of this type of MLC were in the acceptance level based on the Protocols.

Keywords

  1. Graves MN, Thompson AV, Martel MK, McShan DL, Fraass BA. Calibration and quality assurance for rounded leaf-end MLC systems. Med Phys. 2001;28:2227-33. doi: 10.1118/1.1413517. PubMed PMID: 11764026.
  2. Deng J, Pawlicki T, Chen Y, Li J, Jiang SB, Ma CM. The MLC tongue-and-groove effect on IMRT dose distributions. Phys Med Biol. 2001;46:1039-60. PubMed PMID: 11324950.
  3. Sharpe MB, Miller BM, Wong JW. Compensation of x-ray beam penumbra in conformal radiotherapy. Med Phys. 2000;27:1739-45. doi: 10.1118/1.1287283. PubMed PMID: 10984219.
  4. Yang Y, Xing L. Using the volumetric effect of a finite-sized detector for routine quality assurance of multileaf collimator leaf positioning. Med Phys. 2003;30:433-41. doi: 10.1118/1.1543150. PubMed PMID: 12674244.
  5. Bayouth JE, Wendt D, Morrill SM. MLC quality assurance techniques for IMRT applications. Med Phys. 2003;30:743-50. doi: 10.1118/1.1564091. PubMed PMID: 12772980.
  6. LoSasso T, Kutcher GJ. Multileaf collimation versus alloy blocks: analysis of geometric accuracy. Int J Radiat Oncol Biol Phys. 1995;32:499-506.doi: 10.1016/0360-3016(94)00455-t . PubMed PMID: 7751191.
  7. LoSasso T, Chui CS, Kutcher GJ, Leibel SA, Fuks Z, Ling CC. The use of a multi-leaf collimator for conformal radiotherapy of carcinomas of the prostate and nasopharynx. Int J Radiat Oncol Biol Phys. 1993;25:161-70. doi: 10.1016/0360-3016(93)90337-u .PubMed PMID: 8420865.
  8. Galvin JM, Smith AR, Lally B. Characterization of a multi-leaf collimator system. Int J Radiat Oncol Biol Phys. 1993;25:181-92doi: 10.1016/0360-3016(93)90339-w. PubMed PMID: 8420867.
  9. Wang L, Li J, Paskalev K, Hoban P, Luo W, Chen L, et al. Commissioning and quality assurance of a commercial stereotactic treatment-planning system for extracranial IMRT. J Appl Clin Med Phys. 2006;7:21-34.doi: 10.1120/jacmp.2027.25368 . PubMed PMID: 16518314; PubMed Central PMCID: PMC5722476.
  10. Belec J, Patrocinio H, Verhaegen F. Development of a Monte Carlo model for the Brainlab microMLC. Phys Med Biol. 2005;50:787-99. doi: 10.1088/0031-9155/50/5/005. PubMed PMID: 15798255.
  11. Casanova Borca V, Pasquino M, Russo G, Grosso P, Cante D, Sciacero P, et al. Dosimetric characterization and use of GAFCHROMIC EBT3 film for IMRT dose verification. J Appl Clin Med Phys. 2013;14:4111. doi: 10.1120/jacmp.v14i2.4111. PubMed PMID: 23470940; PubMed Central PMCID: PMC5714357.
  12. Farah N, Francis Z, Abboud M. Analysis of the EBT3 Gafchromic film irradiated with 6 MV photons and 6 MeV electrons using reflective mode scanners. Phys Med. 2014;30:708-12. doi: 10.1016/j.ejmp.2014.04.010. PubMed PMID: 24880678.
  13. International Specialty Products (ISP) [Internet]. Gafchromic™ Dosimetry Media, Type EBT-3. Avilale from: http://www.gafchromic.com/documents/EBT3_Specifications.pdf
  14. Niroomand-Rad A, Blackwell CR, Coursey BM, Gall KP, Galvin JM, McLaughlin WL, et al. Radiochromic film dosimetry: recommendations of AAPM Radiation Therapy Committee Task Group 55. American Association of Physicists in Medicine. Med Phys. 1998;25:2093-115. doi: 10.1118/1.598407. PubMed PMID: 9829234.
  15. Chui CS, Spirou S, LoSasso T. Testing of dynamic multileaf collimation. Med Phys. 1996;23:635-41. doi: 10.1118/1.597699. PubMed PMID: 8724734.
  16. Bhardwaj AK, Kehwar TS, Chakarvarti SK, Oinam AS, Sharma SC. Dosimetric and qualitative analysis of kinetic properties of millennium 80 multileaf collimator system for dynamic intensity modulated radiotherapy treatments. J Cancer Res Ther. 2007;3:23-8.doi: 10.4103/0973-1482.31967 . PubMed PMID: 17998715.
  17. Venencia CD, Besa P. Commissioning and quality assurance for intensity modulated radiotherapy with dynamic multileaf collimator: experience of the Pontificia Universidad Catolica de Chile. J Appl Clin Med Phys. 2004;5:37-54.doi: 10.1120/jacmp.2021.25275 . PubMed PMID: 15753938; PubMed Central PMCID: PMC5723486.
  18. Mamalui-Hunter M, Li H, Low DA. MLC quality assurance using EPID: a fitting technique with subpixel precision. Med Phys. 2008;35:2347-55. doi: 10.1118/1.2919560. PubMed PMID: 18649468.
  19. Chang J, Obcemea CH, Sillanpaa J, Mechalakos J, Burman C. Use of EPID for leaf position accuracy QA of dynamic multi-leaf collimator (DMLC) treatment. Med Phys. 2004;31:2091-6. doi: 10.1118/1.1760187. PubMed PMID: 15305462.
  20. Baghani HR, Aghamiri SM, Mahdavi SR, Robatjazi M, Zadeh AR, Akbari ME, et al. Dosimetric evaluation of Gafchromic EBT2 film for breast intraoperative electron radiotherapy verification. Phys Med. 2015;31:37-42. doi: 10.1016/j.ejmp.2014.08.005. PubMed PMID: 25231546.
  21. Falahati F, Nickfarjam A, Shabani M. A feasibility study of IMRT of lung cancer using gafchromic EBT3 film. Journal of Biomedical Physics and Engineering. 2018;8.doi: 10.31661/jbpe.v0i0.791.
  22. Devic S, Seuntjens J, Sham E, Podgorsak EB, Schmidtlein CR, Kirov AS, et al. Precise radiochromic film dosimetry using a flat-bed document scanner. Med Phys. 2005;32:2245-53. doi: 10.1118/1.1929253. PubMed PMID: 16121579.
  23. Sorriaux J, Kacperek A, Rossomme S, Lee JA, Bertrand D, Vynckier S, et al. Evaluation of Gafchromic® EBT3 films characteristics in therapy photon, electron and proton beams. Phys Med. 2013;29:599-606.doi: 10.1016/j.ejmp.2012.10.001.
  24. Antypas C, Floros I, Rouchota M, Armpilia C, Lyra M. MLC positional accuracy evaluation through the Picket Fence test on EBT2 films and a 3D volumetric phantom. J Appl Clin Med Phys. 2015;16:5185. doi: 10.1120/jacmp.v16i2.5185. PubMed PMID: 26103188; PubMed Central PMCID: PMC5690090.
  25. Sumida I, Yamaguchi H, Kizaki H, Koizumi M, Ogata T, Takahashi Y, et al. Quality assurance of MLC leaf position accuracy and relative dose effect at the MLC abutment region using an electronic portal imaging device. J Radiat Res. 2012;53:798-806. doi: 10.1093/jrr/rrs038. PubMed PMID: 22843372; PubMed Central PMCID: PMC3430416.
  26. Klein EE, Hanley J, Bayouth J, Yin FF, Simon W, Dresser S, et al. Task Group 142 report: quality assurance of medical accelerators. Med Phys. 2009;36:4197-212. doi: 10.1118/1.3190392. PubMed PMID: 19810494.
  27. Kirby M, Ryde S, Hall C. Acceptance testing and commissioning of linear accelerators. York, UK: Institute of Physics and Engineering in Medicine. 2006.
  28. Losasso T. IMRT delivery performance with a varian multileaf collimator. Int J Radiat Oncol Biol Phys. 2008;71:S85-8. doi: 10.1016/j.ijrobp.2007.06.082. PubMed PMID: 18406945.
  29. Li J, Zhang X-Z, Gui L-G, Zhang J, Tang X-B, Ge Y, et al. Clinical Feasibility of Leakage and Transmission Radiation Dosimetry Using Multileaf Collimator of ELEKTA Synergy-S Accelerator During Conventional Radiotherapy. Journal of Medical Imaging and Health Informatics. 2016;6:409-15.doi: 10.1166/jmihi.2016.1706.
  30. Das IJ, Desobry GE, McNeeley SW, Cheng EC, Schultheiss TE. Beam characteristics of a retrofitted double-focused multileaf collimator. Med Phys. 1998;25:1676-84. doi: 10.1118/1.598348. PubMed PMID: 9775373.