Measurement of Head Scatter Factor for Linear Accelerators using Indigenously Designed Columnar Mini Phantom

• Autorzy: Appasamy M. , Xavier S. V. , Kuppusamy T. , Velayudham R.

Identyfikatory

DOI

10.2478/v10013-011-0002-7

• Języki publikacji: EN

Abstrakty

EN

A columnar mini phantom is designed as recommended by ESTRO to measure the Head Scatter Factor (S_C) for 6 MV beam of two linear accelerators. The measurement of S_C at different orientations of the chamber, parallel and perpendicular at 1.5 cm depth predicts the deviation of 2.05% and 1.9% for Elekta and Siemens linear accelerators respectively. The measurement of S_C at 1.5 cm is higher compared to 10 cm depth for both the linear accelerators suggesting the electron contamination at 1.5 cm depth. The effect of wedges on S_C yields a significant contribution of 3.5% and 5% for Siemens and Elekta linear accelerators respectively. The collimator exchange effect reveals the opening of upper jaw increases the S_C irrespective of the linear accelerator. The result emphasizes the need of S_C measurement at 10 cm. The presence of wedge influences the S_C value and the SSD has no influence on S_C. The measured S_C values are in good agreement with the published data

Słowa kluczowe

EN

Head Scatter Factor; columnar mini phantom; collimator exchange effect; ion chamber; linear accelerator

• Wydawca: Polskie Towarzystwo Fizyki Medycznej
• Czasopismo: Polish Journal of Medical Physics and Engineering
• Rocznik: 2011
• Tom: Vol. 17, Iss. 1
• Strony: 13--25
• Opis fizyczny: Bibliogr. 21 poz., rys., tab.

Twórcy

autor

Appasamy M.

• Medical Physics Division, Dr.Kamakshi Memorial Hospital, No:1, Radial Road, Pallikaranai, Chennai
• Nuclear and Medical Physics Division, School of Advanced Sciences, VIT University, Vellore

autor

Xavier S. V.

• Medical Physics Division, Dr.Kamakshi Memorial Hospital, No:1, Radial Road, Pallikaranai, Chennai

autor

Kuppusamy T.

• Medical Physics Division, Dr.Kamakshi Memorial Hospital, No:1, Radial Road, Pallikaranai, Chennai

autor

Velayudham R.

• Nuclear and Medical Physics Division, School of Advanced Sciences, VIT University, Vellore

Bibliografia

• [1] Biggs P. J, Ling C. C. Electron as the cause of the observe dmax shift with field size in high energy beams. Med Phys. 1979; 6: 291-295.
• [2] Biggs P J, Russell M. D. An investigation into the presence of secondary electrons in megavoltage photon beams. Phys Med Biol. 1983; 28: 1033-1043.
• [3] Bjarngard B. E, Vadash P. Analysis of central-axis doses for high energy x-rays. Med. Phys. 1995; 22: 1191–1195.
• [4] Ding G. X. An investigations of accelerator head scatter and output factor in air. Med. Phys. 2004; 31: 2527-2533.
• [5] Dutreix A, Bjarngard B. E, Bridier A, Mijnheer B, Shaw J.E, Svensson H. Monitor unit calculation for high energy photon beams. The Netherlands, ESTRO and Garant Publishers, 1997: 101-104.
• [6] Heukelom S, Lanson J. H, Mijnheer B. J. Wedge factor constituents of higher-energy photon beams: head and phantom scatter dose components. Radiother Oncol. 1994; 32: 73-83.
• [7] Holt J. G, Laughlin J. S, Moroney J. P. The extension of the concept of tissue-air ratios (TAR) to high-energy x-ray beams. Radiology. 1970; 96: 437–446
• [8] Johns H. E, Cunningham J. R. The Physics of Radiology. 4th edition. Charles C. Thomas, Springfield. 1983: 336–381.
• [9] Jursinic P A, Measurement of head scatter factors of linear accelerators with columnar miniphantoms. Med Phys. 2006; 33: 1720-1728.
• [10] Karzmark C J, Deubert A, Loevinger R. Tissue-phantom ratios—An aid to treatment planning. Brit J Radiol. 1965; 38: 158–159.
• [11] Khan F M, Sewchand W, Lee J, Williamson J F. Revision of tissue-maximum ratio and scatter-maximum ratio concepts for cobalt 60 and higher energy x-ray beams. Med. Phys. 1980; 7: 230–237.
• [12] Luxton G, Astrahan M A. Characteristics of high energy photon beam of a 25 MV accelerator. Med Phys. 1988; 15: 82-87.
• [13] Luxton G, Astrahan M A, Output factor constituents of a high energy photon beam. Med Phys. 1988; 15: 88-91.
• [14] Mackie T R, Scrimger J W. Contamination of a 15-MV photon beam by electrons and scattered photons. Radiology. 1982; 144: 403-409.
• [15] McKenzie A L, Stevens P H. Twenty-five years of MTRP—A theoretical and experimental analysis. Phys Med Biol. 1995; 40: 17–29.
• [16] Sjogren R, Karlsson M. Electron contamination in clinical high energy photon beams. Med Phys. 1996; 23: 1873-1881.
• [17] Tatcher M, Bjarngard B E. Head-scatter factors in rectangular photon fields. Med Phys. 1993; 20: 205-206.
• [18] Van Gasteren J J M, Heukelom S, Jager H N, Mijnheer B J, van Kleffens H J, van der Laarse R. et al. Determination and use of scatter correction factors of megavoltage photon beams. Netherlands Commission on Radiation Dosimetry. NCS Report No. 12. 1998.
• [19] Venselaar J, Heukelom S, Jager N, Mijnheer B, van der Laarse R, van Gasteren H, et al. Effect of electron contamination on scatter correction factors for photon beam dosimetry. Med Phys. 1999; 26: 2099-2106.
• [20] Weber L, Nilsson P, Ahnesjo A. Build-up cap materials for measurements of photon head-scatter factors, Phys Med Biol. 1997; 42: 1875-1886.
• [21] Zhu T C, Lam K L, Li X A, Charlie Ma C-M, Palta J R, et al. Report of AAPM Therapy Physic Committee task Group 74: In-air output ratio, SC, for megavoltage photon beams. Med Phys. 2009; 36: 5261-5291.