Output factor determination based on Monte Carlo simulation for small cone field in 10-MV photon beam
- 51 Downloads
The difficulty of measuring output factor (OPF) in a small field has been frequently discussed in recent publications. This study is aimed to determine the OPF in a small field using 10-MV photon beam and stereotactic conical collimator (cone). The OPF was measured by two diode detectors (SFD, EDGE detector) and one micro-ion chamber (PinPoint 3D chamber) in a water phantom. A Monte Carlo simulation using simplified detector model was performed to obtain the correction factor for the detector measurements. About 12% OPF difference was observed in the measurement at the smallest field (7.5 mm diameter) for EDGE detector and PinPoint 3D chamber. By applying the Monte Carlo-based correction factor to the measurement, the maximum discrepancy among the three detectors was reduced to within 3%. The results indicate that determination of OPF in a small field should be carefully performed. Especially, detector choice and appropriate correction factor application are very important in this regard.
KeywordsDosimetry Monte Carlo SRS Small field
The authors would like to thank the radiotherapy-related staffs in Juntendo University Hospital for giving us the opportunity for fruitful measurement.
Compliance with ethical standards
Conflict of interest
We have no conflicts of interest to declare for this study.
Statement of human and animal rights
There is no animal or humans involved in this study.
There are no human subjects involved in this work.
- 1.Schell MC, Bova FJ, Larson DA, Leavitt DD, Lutz WR, Podgorsak EB, Wu A (1995) Stereotactic Radiosurgery Report of Task Group 42 Radiation Therapy Committee. Oncol 54:.Google Scholar
- 3.Benedict SH, Yenice KM, Followill D, Galvin JM, Hinson W, Kavanagh B, Keall P, Lovelock M, Meeks S, Papiez L, Purdie T, Sadagopan R, Schell MC, Salter B, Schlesinger DJ, Shiu AS, Solberg T, Song DY, Stieber V, Timmerman R, Tomé WA, Verellen D, Wang L, Yin F-F, Tomé WA, Verellen D, Wang L, Yin F-F. Stereotactic body radiation therapy: the report of AAPM Task Group 101. Med Phys. 2010;37:4078–101. https://doi.org/10.1118/1.3438081.CrossRefPubMedGoogle Scholar
- 8.Das IJ, Cheng C-W, Watts RJ, Ahnesjö A, Gibbons J, Li XA, Lowenstein J, Mitra RK, Simon WE, Zhu TC. Accelerator beam data commissioning equipment and procedures: report of the TG-106 of the Therapy Physics Committee of the AAPM. Med Phys. 2008;35:4186. https://doi.org/10.1118/1.2969070.CrossRefPubMedGoogle Scholar
- 14.Francescon P, Kilby W, Satariano N. Monte Carlo simulated correction factors for output factor measurement with the CyberKnife system—results for new detectors and correction factor dependence on measurement distance and detector orientation. Phys Med Biol. 2014;59:N11–7. https://doi.org/10.1088/0031-9155/59/6/N11.CrossRefPubMedGoogle Scholar
- 22.Weston S, Evans JA, Sidhu NP, Cranmer-Sargison G, Weston S, Evans JA, Sidhu NP, Thwaites DI. Monte Carlo modelling of diode detectors for small field MV photon dosimetry: detector model simplification and the sensitivity of correction factors to source parameterization. Phys Med Biol. 2012;57:5141. https://doi.org/10.1088/0031-9155/57/16/5141.CrossRefPubMedGoogle Scholar
- 24.Kawrakow I, Rogers DWO. The EGSnrc Code System: Monte Carlo Simulation of Electron and Photon Transport, NRCC Report PIRS-701, 2000.Google Scholar
- 25.Rogers DWO, Walters B, Kawrakow I. BEAMnrc Users Manual, NRCC Report PIRS-0509. Stand: Ioniz Radiat; 2005.Google Scholar
- 28.Hirayama H, Namito Y, Bielajew AF, Wilderman SJ, Nelson WR (2005) The EGS5 Code System, SLAC-Report-730 and KEK Report 2005-8. SLAC National Accelerator Laboratory and High Energy Accelerator Research Organization.Google Scholar
- 29.ICRU Report No.37 Stopping powers for electrons and positrons. In: International Commission on Radiation Units and Measurements. WashingtonGoogle Scholar
- 30.Mainegra-Hing E (2017) User Manual for egs inprz, a GUI for the NRC RZ user-codes. NRCC Rep PIRS-801(RevB) 801:1–35.Google Scholar
- 37.Bassinet C, Huet C, Derreumaux S, Brunet G, Chéa M, Baumann M, Lacornerie T, Gaudaire-Josset S, Trompier F, Roch P, Boisserie G, Clairand I. Small fields output factors measurements and correction factors determination for several detectors for a CyberKnife® and linear accelerators equipped with microMLC and circular cones. Med Phys. 2013;40:71725. https://doi.org/10.1118/1.4811139.CrossRefGoogle Scholar
- 38.Shimono T, Koshida K, Hidekazu A, Ae N, Matsubara K, Hiroshi A, Ae T, Okuda H, Nambu H, Matsubara K, Takahashi H, Okuda H. Polarity effect in commercial ionization chambers used in photon beams with small fields. Radiol Phys Technol. 2009;2:97–103. https://doi.org/10.1007/s12194-008-0050-1.CrossRefPubMedGoogle Scholar