Abstract
Backscatter factors are essential in the determination of radiation dose for kilovoltage X-ray beams. The accurate measurement of backscatter factors in water (B W) is difficult and published values are based largely on Monte Carlo calculations. A number of studies have found that the measurement of B W in the energy range from 50 to 300 kVp is possible using Gafchromic EBT film, but this film is no longer commercially available. In this work, we evaluated whether the newer Gafchromic EBT2 film is suitable for the determination of B W for kilovoltage X-ray beams. B W were measured with Gafchromic EBT2 film for beam qualities of 50, 100 and 280 kVp and field sizes of 2, 3, 4 and 6 cm diameter and compared with tabulated values published in the AAPM TG-61 protocol. We found that rotation of the film position during readout had a small but non-negligible effect on the optical density readings. The agreement between measured and published B W was better than 3%, with the largest difference of occurring for the 2 cm diameter field with the 50 kVp X-ray beam. However, these differences are consistent with the total estimated uncertainty for the measurements, as calculated by the ISO GUM. Our results demonstrate that Gafchromic EBT2 film is a suitable dosimeter for B W measurements for clinical kilovoltage X-ray beams.
Similar content being viewed by others
References
Khan FM (1994) The physics of radiation therapy. Williams and Wilkins, Baltimore
Aukett RJ, Burns JE, Greener AG, Harrison RM, Moretti C, Nahum AE, Rosser KE (2005) Addendum to the IPEMB code of practice for the determination of absorbed dose for X-rays below 300 kV generating potential (0.035 mm Al-4 mm Cu HVL). Phys Med Biol 50(12):2739–2748
Klevenhagen SC, Aukett RJ, Harrison RM, Moretti C, Nahum AE, Rosser KE (1996) The IPEMB code of practice for the determination of absorbed dose for X-rays below 300 kV generating potential (0.035 mm Al-4 mm Cu HVL; 10–300 kV generating potential). Phys Med Biol 41(12):2605–2625
Ma CM, Coffey CW, DeWerd LA, Liu C, Nath R, Seltzer SM, Seuntjens JP (2001) AAPM protocol for 40–300 kV X-ray beam dosimetry in radiotherapy and radiobiology. Med Phys 28(6):868–893
Mayles P (2007) Kilovoltage X-rays. In: Mayles P, Nahum AE, Rosenwald J (eds) Handbook of radiotherapy physics. CRC Press, Boca Raton, pp 439–449
Grosswendt B (1993) Dependence of the photon backscatter factor for water on irradiation field size and source-to-phantom distances between 1.5 and 10 cm. Phys Med Biol 38(2):305–310
Chica U, Anguiano M, Lallena AM (2008) Study of the formalism used to determine the absorbed dose for low-energy X-ray beams. Phys Med Biol 53(23):6963–6977
Healy BJ, Sylvander S, Nitschke KN (2008) Dose reduction from loss of backscatter in superficial X-ray radiation therapy with the Pantak SXT 150 unit. Austral Phys Eng Sci Med 31(1):49–55
Hill R, Healy B, Holloway L, Baldock C (2007) An investigation of dose changes for therapeutic kilovoltage X-ray beams with underlying lead shielding. Med Phys 34(7):3045–3053
Klevenhagen SC (1989) Experimentally determined backscatter factors for X-rays generated at voltages between 16 and 140 kV. Phys Med Biol 34(12):1871–1882
Ma CM, Seuntjens JP (1999) Mass-energy absorption coefficient and backscatter factor ratios for kilovoltage X-ray beams. Phys Med Biol 44(1):131–143
Klevenhagen SC, Aukett RJ, Burns JE, Harrison RM, Knight RT, Nahum AE, Rosser KE (1991) Memorandum from the Institute of Physical Sciences in Medicine Back-scatter and F-factors for low- and medium-energy X-ray beams in radiotherapy. Br J Radiol 64(765):836–841
Carlsson CA (1993) Differences in reported backscatter factors for low-energy X-rays: a literature study. Phys Med Biol 38(4):521
Coudin D, Marinello G (1998) Lithium borate TLD for determining the backscatter factors for low- energy X rays: comparison with chamber-based and Monte Carlo derived values. Med Phys 25(3):347–353
Klevenhagen SC (1982) The build-up of backscatter in the energy range 1 mm Al to 8 mm Al HVT (radiotherapy beams). Phys Med Biol 27(8):1035–1043
Harrison RM, Walker C, Aukett RJ (1990) Measurement of backscatter factors for low energy radiotherapy (0.1–2.0 mm Al HVL) using thermoluminescence dosimetry. Phys Med Biol 35(9):1247
Tomljenovic II, Ninkovic MM, Bek-Uzarov D, Stankovic SJ, Kovacevic M (1999) Water phantom backscatter factors for X-rays in the 60 kV to 300 kV region. Phys Med Biol 44(9):2193–2200
Kim MS, Ryu JS, Park S, Yi Y (2006) Comparison of measured backscatter factors with Monte Carlo simulations for low energy X-ray. Nucl Instrum Methods Phys Res A 567(1):341–344
Grosswendt B (1984) Backscatter factors for X-rays generated at voltages between 10 and 100 kV. Phys Med Biol 29(5):579–591
Petoussi-Henss N, Zankl M, Drexler G, Panzer W, Regulla D (1998) Calculation of backscatter factors for diagnostic radiology using Monte Carlo methods. Phys Med Biol 43(8):2237
Knight RT (1994) Backscatter factors for low and medium energy X-rays calculated by the Monte Carlo method. Royal Marsden NHS Trust, Sutton
Munck Af Rosenschold P, Nilsson P, Knoos T (2008) Kilovoltage X-ray dosimetry-an experimental comparison between different dosimetry protocols. Phys Med Biol 53(16):4431–4442
Cheung T, Butson MJ, Yu PKN (2004) Experimental energy response verification of XR type T radiochromic film. Phys Med Biol 49(21):N371–N376
Butson MJ, Cheung T, Yu PKN (2006) Weak energy dependence of EBT gafchromic film dose response in the 50 kVp–10 MVp X-ray range. Appl Radiat Isot 64(1):60–62
Chiu-Tsao ST, Ho Y, Shankar R, Wang L, Harrison LB (2005) Energy dependence of response of new high sensitivity radiochromic films for megavoltage and kilovoltage radiation energies. Med Phys 32(11):3350–3354
Rink A, Vitkin IA, Jaffray DA (2007) Energy dependence (75 kVp to 18 MV) of radiochromic films assessed using a real-time optical dosimeter. Med Phys 34(2):458–463
Butson MJ, Cheung T, Yu PK, Price S, Bailey M (2008) Measurement of radiotherapy superficial X-ray dose under eye shields with radiochromic film. Phys Med 24(1):29–33
Butson MJ, Cheung T, Yu PKN (2007) Radiochromic film for verification of superficial X-ray backscatter factors. Austral Phys Eng Sci Med 30(4):269–273
Fletcher CL, Mills JA (2008) An assessment of GafChromic film for measuring 50 kV and 100 kV percentage depth dose curves. Phys Med Biol 53(11):N209–N218
Kim J, Hill R, Claridge MacKonis E, Kuncic Z (2010) An investigation of backscatter factors for kilovoltage X-rays: a comparison between Monte Carlo simulations and Gafchromic EBT film measurements. Phys Med Biol 55(3):783–797
Arjomandy B, Tailor R, Anand A, Sahoo N, Gillin M, Prado K, Vicic M (2010) Energy dependence and dose response of Gafchromic EBT2 film over a wide range of photon, electron, and proton beam energies. Med Phys 37(5):1942–1947
Hartmann B, Martišíková M, Jäkel O (2010) Technical note: homogeneity of gafchromic® EBT2 film. Med Phys 37(4):1753–1756
Richley L, John AC, Coomber H, Fletcher S (2010) Evaluation and optimization of the new EBT2 radiochromic film dosimetry system for patient dose verification in radiotherapy. Phys Med Biol 55(9):2601–2617
Sutherland JGH, Rogers DWO (2010) Monte Carlo calculated absorbed-dose energy dependence of EBT and EBT2 film. Med Phys 37(3):1110–1116
Lindsay P, Rink A, Ruschin M, Jaffray D (2010) Investigation of energy dependence of EBT and EBT-2 Gafchromic film. Med Phys 37(2):571–576
Devic S, Seuntjens J, Abdel-Rahman W, Evans M, Olivares M, Podgorsak EB, Vuong T, Soares CG (2006) Accurate skin dose measurements using radiochromic film in clinical applications. Med Phys 33(4):1116–1124
Lye JE, Butler DJ, Webb DV (2010) Enhanced epidermal dose caused by localized electron contamination from lead cutouts used in kilovoltage radiotherapy. Med Phys 37(8):3935–3939
Hill R, Kuncic Z, Baldock C (2010) The water equivalence of solid phantoms for low energy photon beams. Med Phys 37(8):4355–4363
Healy BJ, Gibbs A, Murry RL, Prunster JE, Nitschke KN (2005) Output factor measurements for a kilovoltage X-ray therapy unit. Austral Phys Eng Sci Med 28(2):115–121
Hill R, Holloway L, Baldock C (2005) A dosimetric evaluation of water equivalent phantoms for kilovoltage X-ray beams. Phys Med Biol 50(21):N331–N344
Gorjiara T, Hill R, Kim JH, Kuncic Z, Adamovics J, Baldock C (2010) Study of dosimetric water equivalency of PRESAGE® for megavoltage and kilovoltage X-ray beams. J Phys Conf Ser 250:244–248
Butson MJ, Mathur J, Metcalfe PE (1995) Dose characteristics of a new 300 kVp orthovoltage machine. Austral Phys Eng Sci Med 18(3):133–138
Lee CHM, Chan KKD (2000) Electron contamination from the lead cutout used in kilovoltage radiotherapy. Phys Med Biol 45(1):1–8
Klevenhagen SC, D’Souza D, Bonnefoux I (1991) Complications in low energy X-ray dosimetry caused by electron contamination. Phys Med Biol 36(8):1111–1116
Andreo P, Burns DT, Hohlfield K, Huq MS, Kanai T, Laitano F, Smyth V, Vynckier S (2000) Absorbed dose determination in external beam radiotherapy, An International Code of Practice for Dosimetry Based on Standards of Absorbed Dose to Water, Technical Report Series No. 398. International Atomic Energy Agency, Vienna
ISO (1995) Guide to the expression of uncertainties in measurement. International Organisation for Standardization, Geneva
McEwen MR, Kawrakow I, Ross CK (2008) The effective point of measurement of ionization chambers and the build-up anomaly in MV X-ray beams. Med Phys 35(3):950–958
Desroches J, Bouchard H, Lacroix F (2010) Technical note: Potential errors in optical density measurements due to scanning side in EBT and EBT2 Gafchromic film dosimetry. Med Phys 37(4):1565–1570
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Smith, L., Hill, R., Nakano, M. et al. The measurement of backscatter factors of kilovoltage X-ray beams using Gafchromic™ EBT2 film. Australas Phys Eng Sci Med 34, 261–266 (2011). https://doi.org/10.1007/s13246-011-0073-5
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s13246-011-0073-5