Abstract
With rapid technological improvements in computer driven 3-D radiotherapy treatment planning systems (RTPS) the use of compensating filters for intensity modulated radiation therapy (IMRT) will dramatically increase the ease of treatment. The procedure for commissioning .decimal™ (Sanford, Florida) compensators involved the measurement of the effective linear attenuation coefficients for aluminium and brass. Field sizes to be measured vary from small square field size of 5 cm to the larger square field size of 25 cm with additional measurements at each 5 cm2 increments. The energies commissioned where 6 MV and 18 MV photons. The depth of measurements varied from 5 cm to 10 cm within phantom material and the source surface distance varied from 100 cm to 90 cm. The beam quality was measured by obtaining percentage depth dose (PDD) curves for the various field sizes with and without the compensating material. Results of the series of measurements showed no significant differences in the effective linear attenuation coefficients with respect to chamber depth and source surface distance with constant energy and field size. The main factor that was shown to influence the effective linear attenuation coefficient was field size variation. A correlation was shown between the effective linear attenuation coefficient and field size, up to a field size of 15 cm x 15 cm. Our results showed that for optimal patient treatments using IMRT compensating filters, there is a need for establishing two field size dependent linear attenuation coefficients.
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References
Van Dyk, J.,The modern technology of radiation oncology, A compendium for medical physicists and radiation oncologists, Volume 1, Medical Physics Publishing, Madison, 451–455, 1999.
Van Dyk, J.,The modern technology of radiation oncology, A compendium for medical physicists and radiation oncologists, Volume 2, Medical Physics Publishing, Madison, 226, 2005.
Levitt, S.H., Purdy, J.A., Perez, C.A. and Vijayakumar, S.,Technical basis of radiation therapy practical clinical applications, 4th revised edition, Springer, Germany, 95, 211, 172–3, 2006
Dimitriadis, D.M. and Fallone, B.G.,Compensators for intensity-modulated beams, Medical Dosimetry, 27(3):215–220, 2002.
Sethi, A., Leybovich, L., Dogan, N. and Glasgow, G.,Effectiveness of compensating filters in the presence of tissue inhomogeneities, Journal of Applied Clinical Medical Physics, 4(3):209–216, 2003.
Chang, S.X., Cullip, T.J., Deschesne, K.M., Miller, E.P. and Rosenman, J.G.,Compensators: An alternative IMRT delivery technique, Journal of Applied Clinical Medical Physics, 5(3):15–36, 2004.
Kanematsu, K., Asakura, H., Kohno, R. and Takahashi, O.,Tumour shapes and fully automated range compensation for heavy charged particle radiotherapy, Phys. Med. Biol., 49:N1-N5, 2004.
Metcalfe, P., Kron, T. and Hoban, P.,The physics of radiotherapy x-rays from linear accelerators, Medical Physics Publishing, Madison, 34, 39, 230, 268–270, 315, 346–350, 3rd printing 2004.
Williams, J.R. and Thwaites, D.I.,Radiotherapy physics in practice, 2nd ed., Oxford University Press, Oxford, 175–176, 200, re-printed 2004.
CMS,decimal Commissioning Guide, decimal, Inc. U.S.A, 2005.
IAEA,Technical Reports Series No. 398 — Absorbed Dose Determination in External Beam Radiotherapy — An international code of practice for dosimetry based on standards of absorbed dose to water, International Atomic Energy Agency, Vienna, 68–71, 2000.
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Bartrum, T., Bailey, M., Nelson, V. et al. Linear attenuation coefficients for compensator based imrt. Australas. Phys. Eng. Sci. Med. 30, 281–287 (2007). https://doi.org/10.1007/BF03178438
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DOI: https://doi.org/10.1007/BF03178438