Evaluating the Performance of Various Detectors in the Small Field Size by 6 MV Linac

Document Type : Technical Notes

Author

Department of Radiation Oncology, King Hussein Cancer Center, Queen Rania St 202, Amman, Jordan Department of Physics, Faculty of Science, Al-Balqa Applied University, P.O.Box: Al-Salt 19117, Jordan

Abstract

Introduction: We present a comprehensive evaluation of three different dosimeters in 6 MV flattening filter-free beam (FFF) under charged particle dis-equilibrium conditions.
Material and Methods: Diamond detector, Gafchromic film, and Un-shielded diode detector were used in this study. The total scatters factor of Jaw-shaped fields was measured starting from (10x10 cm2) down to (0.5x0.5 cm2) using True Beam Linear Accelerator (Varian) and solid water phantom. 
Results: The diamond detector presented more accurate results at an ultra-small field size (0.5x0.5 cm2) with a 14.1% deviation of the diode results. On the other hand, all the measurements ranged within 5% for large field sizes “i.e. Larger than 4.0x4.0 cm2”. The relative output factor (ROF) was introduced as a total scatter factor measured by a given dosimeter (x) to total scatter factor measured by diamond detector , the relative output factor values were 0.859 and 0.104 for both Diode/Diamond  and Film/Diamond , combinations, respectively.
Conclusion: We found that the diamond detector is the most appropriate detector for the small field dosimetry with high accuracy.

Keywords

Main Subjects

References

  1. Masanga W, Tangboonduangjit P, Khamfongkhruea C, Tannanonta C. Determination of small field output factors in 6 and 10 MV flattening filter free photon beams using various detectors. InJournal of Physics: Conference Series 2016 Mar 1 ; 694(1): 012027.
  2. Sharma SD. Unflattened photon beams from the standard flattening filter free accelerators for radiotherapy: Advantages, limitations and challenges. Journal of Medical Physics/Association of Medical Physicists of India. 2011 Jul;36(3):123.
  3. Kragl G, af Wetterstedt S, Knäusl B, Lind M, McCavana P, Knöös T, et al. Dosimetric characteristics of 6 and 10 MV unflattened photon beams. Radiotherapy and Oncology. 2009 Oct 1;93(1):141-6.
  4. Hrbacek J, Lang S, Klöck S. Commissioning of photon beams of a flattening filter-free linear accelerator and the accuracy of beam modeling using an anisotropic analytical algorithm. International Journal of Radiation Oncology* Biology* Physics. 2011 Jul 15;80(4):1228-37.
  5. Huq MS, Hwang MS, Teo TP, Jang SY, Heron DE, Lalonde RJ. A dosimetric evaluation of the IAEA‐AAPM TRS 483 code of practice for dosimetry of small static fields used in conventional linac beams and comparison with IAEA TRS‐398, AAPM TG 51, and TG 51 Addendum protocols. Medical physics. 2018 Sep;45(9):4257-73.
  6. Dai X, Zhao Y, Liang Z, Dassarath M, Wang L, Jin L, et al. Volumetric-modulated arc therapy for oropharyngeal carcinoma: a dosimetric and delivery efficiency comparison with static-field IMRT. Physica Medica. 2015 Feb 1;31(1):54-9.
  7. Georg D, Knöös T, McClean B. Current status and future perspective of flattening filter free photon beams. Medical physics. 2011 Mar;38(3):1280-93.
  8. Das IJ, Ding GX, Ahnesjö A. Small fields: nonequilibrium radiation dosimetry. Medical physics. 2008 Jan;35(1):206-15.
  9. Charles PH, Cranmer‐Sargison G, Thwaites DI, Crowe SB, Kairn T, Knight RT, et al. A practical and theoretical definition of very small field size for radiotherapy output factor measurements. Medical physics. 2014 Apr;41(4):041707.
  10. Al Atawneh S. Analytical Formula for the total scatter factor of the Small Radiation Field Size. 2021; 7(3): 152-60.
  11. Al Atawneh SJ. Empirical Formalism for the Phantom Scatter Factor of Small Fields: Using Different Density Media. International Journal of Medical Physics, Clinical Engineering and Radiation Oncology. 2021 Dec 24;11(1):36-47.
  12. Parwaie W, Refahi S, Ardekani MA, Farhood B. Different dosimeters/detectors used in small-field dosimetry: Pros and cons. Journal of medical signals and sensors. 2018 Jul;8(3):195-203.
  13. Lechner W, Palmans H, Sölkner L, Grochowska P, Georg D. Detector comparison for small field output factor measurements in flattening filter free photon beams. Radiotherapy and oncology. 2013 Dec 1;109(3):356-60.
  14. Dwivedi S, Kansal S, Dangwal VK, Bharati A, Shukla J. Dosimetry of a 6 MV flattening filter-free small photon beam using various detectors. Biomedical Physics & Engineering Express. 2021 May 11;7(4):045004.
  15. Zhu TC, Ahnesjö A, Lam KL, Li XA, Ma CM, Palta JR, et al. Report of AAPM Therapy Physics Committee Task Group 74: in‐air output ratio, for megavoltage photon beams. Medical physics. 2009 Nov;36(11):5261-91.
  16. Nahum AE. Perturbation effects in dosimetry: Part I. Kilovoltage x-rays and electrons. Physics in Medicine & Biology. 1996 Sep 1;41(9):1531.
  17. Laub WU, Wong T. The volume effect of detectors in the dosimetry of small fields used in IMRT. Medical physics. 2003 Mar;30(3):341-7.
  18. Ding GX, Duggan DM, Coffey CW. Commissioning stereotactic radiosurgery beams using both experimental and theoretical methods. Physics in Medicine & Biology. 2006 May 4;51(10):2549.
  19. Sauer OA, Wilbert J. Measurement of output factors for small photon beams. Medical physics. 2007 Jun;34(6Part1):1983-8.
  20. Klein DM, Tailor RC, Archambault L, Wang L, Therriault‐Proulx F, Beddar AS. Measuring output factors of small fields formed by collimator jaws and multileaf collimator using plastic scintillation detectors. Medical physics. 2010 Oct;37(10):5541-9.
  21. Bassinet C, Huet C, Derreumaux S, Brunet G, Chéa M, Baumann M, et al. Small fields output factors measurements and correction factors determination for several detectors for a CyberKnife® and linear accelerators equipped with microMLC and circular cones. Medical physics. 2013 Jul;40(7):071725.
  22. Nasir MK, Amjad N, Razzaq A, Siddique T. Measurement and analysis of PDDs profile and output factors for small field sizes by CC13 and micro-chamber CC01. International Journal of Medical Physics, Clinical Engineering and Radiation Oncology. 2017;6(01):36.
  23. Islam MR, Watabe H, Stefano A. Measurement and Comparison of Output Factors Using Two Detectors for NOVAC7 IntraOperative Radiotherapy Accelerator. International Journal of Medical Physics, Clinical Engineering and Radiation Oncology. 2020 Mar 25;9(2):52-61.
  24. Dufreneix S, Di Bartolo C, Bremaud M, Mesgouez J, Legrand C, Autret D. P10. How to choose a detector for small fields measurements?. Physica Medica: European Journal of Medical Physics. 2016 Dec 1;32:371.

 

 

 

 

 

 

Iranian Journal of Medical Physics
Volume 20, Issue 1
January and February 2023
Pages 1-6

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History

  • Receive Date: 14 February 2022
  • Revise Date: 25 April 2022
  • Accept Date: 29 April 2022

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