Dosimetry and evaluating the effect of treatment parameters on the leakage of multi leaf collimators in ONCOR linear accelerators

Document Type : Original Article


1 Department of Medical Physics and Medical Engineering, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran

2 Department of Radiation Oncology, Isfahan Milad Hospital, Isfahan, Iran


Background: One of the standard equipment in medical linear accelerators is multi-leaf collimators (MLCs); which is used as a replacement for lead shielding. MLC's advantages are a reduction of the treatment time, the simplicity of treatment, and better dose distribution. The main disadvantage of MLC is the radiation leakages from the edges and between the leaves. The purpose of this study was to determine the effect of various treatment parameters in the magnitude of MLC leakage in linear accelerators.
Materials and Methods: This project was performed with ONCOR Siemens linear accelerators. The amount of radiation leakage was determined by film dosimetry method. The films were Kodak-extended dose range-2, and the beams were 6 MV and 18 MV photons. In another part of the experiment, the fluctuation of the leakage was measured at various depths and fields.
Results: The amount of leakage was generally up to 1.5 ± 0.2% for both energies. The results showed that the level of the leakage and the amount of dose fluctuation depends on the field size and depth of measurement. The amount of the leakage fluctuations in all energies was decreased with increasing of field size. The variation of the leakage versus field size was similar to the inverse of scattering collimator factor.
Conclusions: The amount of leakage was more for 18 MV compare to 6 MV The percentage of the leakage for both energies is less than the 5% value which is recommended by protocols. The fluctuation of the MLC leakage reduced by increasing the field size and depth.


Sadjadi A, Nouraie M, Mohagheghi MA, Mousavi-Jarrahi A, Malekezadeh R, Parkin DM. Cancer occurrence in Iran in 2002, an international perspective. Asian Pac J Cancer Prev 2005;6:359-63.  Back to cited text no. 1
Jemal A, Siegel R, Ward E, Hao Y, Xu J, Murray T, et al. Cancer statistics. CA Cancer J Clin 2008;58:71-96.  Back to cited text no. 2
Suit H, Goldberg S, Niemierko A, Ancukiewicz M, Hall E, Goitein M, et al. Secondary carcinogenesis in patients treated with radiation: A review of data on radiation-induced cancers in human, non-human primate, canine and rodent subjects. Radiat Res 2007;167:12-42.  Back to cited text no. 3
Taylor ML, Kron T. Consideration of the radiation dose delivered away from the treatment field to patients in radiotherapy. J Med Phys 2011;36:59-71.  Back to cited text no. 4
[PUBMED]  Medknow Journal  
Yavari P, Hislop TG, Bajdik C, Sadjadi A, Nouraie M, Babai M, et al. Comparison of cancer incidence in Iran and Iranian immigrants to British Columbia, Canada. Asian Pac J Cancer Prev 2006;7:86-90.  Back to cited text no. 5
Galvin JM, Smith AR, Lally B. Characterization of a multileaf collimator system. Int J Radiat Oncol Biol Phys 1993;25:181-92.  Back to cited text no. 6
Jordan TJ, Williams PC. The design and performance characteristics of a multileaf collimator. Phys Med Biol 1994;39:231-51.  Back to cited text no. 7
Siochi RA. Leakage reduction for the Siemens Moduleaf. J Appl Clin Med Phys 2009;10:2894.  Back to cited text no. 8
Committee ART, Boyer A. Basic applications of multileaf collimators: American Association of Physicists in Medicine Madison; 2001.  Back to cited text no. 9
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.  Back to cited text no. 10
Du MN, Yu CX, Symons M, Yan D, Taylor R, Matter RC, et al. A multifeaf collimator field prescription preparation system for conventional radiotherapy. Inte J Radiat Oncol Biol Phys 1995;32:513-20.  Back to cited text no. 11
Hariri S, Shahriari M. Suggesting a new design for multileaf collimator leaves based on Monte Carlo simulation of two commercial systems. J Appl Clin Med Phys 2010;11:3101.  Back to cited text no. 12
Jeraj M, Robar V. Multileaf collimator in radiotherapy. Radiology and Oncology. 2004;38(3).  Back to cited text no. 13
Rassiah-Szegedi P, Szegedi M, Sarkar V, Streitmatter S, Huang YJ, Zhao H, et al. Dosimetric impact of the 160 MLC on head and neck IMRT treatments. J Appl Clin Med Phys 2014;15:4770.  Back to cited text no. 14
Lonski P, Taylor ML, Franich RD, Harty P, Kron T. Assessment of leakage doses around the treatment heads of different linear accelerators. Radiat Prot Dosimetry 2012;152:304-12.  Back to cited text no. 15
Thompson CM, Weston SJ, Cosgrove VC, Thwaites DI. A dosimetric characterization of a novel linear accelerator collimator. Med Phys 2014;41:031713.  Back to cited text no. 16
Klein EE, Harms WB, Low DA, Willcut V, Purdy JA. Clinical implementation of a commercial multileaf collimator: Dosimetry, networking, simulation, and quality assurance. Int J Radiat Oncol Biol Phys 1995;33:1195-208.  Back to cited text no. 17
Powers WE, Kinzie JJ, Demidecki AJ, Bradfield JS, Feldman A. A New System of Field Shaping for External-Beam Radiation Therapy 1. Radiology. 1973;108:407-11.  Back to cited text no. 18
Galvin JM, editor The multileaf collimator: A complete guide. Proc AAPM annual meeting; 1999.  Back to cited text no. 19
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.  Back to cited text no. 20
Xu XG, Bednarz B, Paganetti H. A review of dosimetry studies on external-beam radiation treatment with respect to second cancer induction. Phys Med Biol 2008;53:R193-241.  Back to cited text no. 21
Podgorsak MB, Kubsad SS, Paliwal BR. Dosimetry of large wedged high-energy photon beams. Med Phys 1993;20(2 Pt 1):369-73.  Back to cited text no. 22
Tailor RC, Followill DS, Hanson WF. A first order approximation of field-size and depth dependence of wedge transmission. Med Phys 1998;25:241-4.  Back to cited text no. 23
Arnfield MR, Siebers JV, Kim JO, Wu Q, Keall PJ, Mohan R. A method for determining multileaf collimator transmission and scatter for dynamic intensity modulated radiotherapy. Med Phys 2000;27:2231-41.  Back to cited text no. 24
Faddegon BA, O'Brien P, Mason DL. The flatness of Siemens linear accelerator x-ray fields. Med Phys 1999;26:220-8.  Back to cited text no. 25
Takahashi S. Conformation radiotherapy. Rotation techniques as applied to radiography and radiotherapy of cancer. Acta Radiol Diagn (Stockh) 1965:Suppl 242:1.  Back to cited text no. 26
Tubiana M. Can we reduce the incidence of second primary malignancies occurring after radiotherapy? A critical review. Radiother Oncol 2009;91:4-15.  Back to cited text no. 27
Zhu XR, Jursinic PA, Grimm DF, Lopez F, Rownd JJ, Gillin MT. Evaluation of Kodak EDR2 film for dose verification of intensity modulated radiation therapy delivered by a static multileaf collimator. Med Phys 2002;29:1687-92.  Back to cited text no. 28
Childress NL, Rosen II. Effect of processing time delay on the dose response of Kodak EDR2 film. Med Phys 2004;31:2284-8.  Back to cited text no. 29
Childress NL, Salehpour M, Dong L, Bloch C, White RA, Rosen II. Dosimetric accuracy of Kodak EDR2 film for IMRT verifications. Med Phys 2005;32:539-48.  Back to cited text no. 30
Ma CM, Pawlicki T, Jiang SB, Li JS, Deng J, Mok E, et al. Monte Carlo verification of IMRT dose distributions from a commercial treatment planning optimization system. Phys Med Biol 2000;45:2483-95.  Back to cited text no. 31
Klüter S, Sroka-Perez G, Schubert K, Debus Jr. Leakage of the Siemens 160 MLC multileaf collimator on a dual energy linear accelerator. Phys Med Biol 2011;56:N29-37.  Back to cited text no. 32