Document Type: Original Research
Assistant professor, Department of Medical Physics and Radiotherapy, Arak University of Medical Sciences, Arak, Iran
Professor, Department of Medical Physics and Radiotherapy, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
Background: In this study, a method for linear attenuation coefficient calculation was introduced.Methods: Linear attenuation coefficient was calculated with a new method that base on the physics of interaction of photon with matter, mathematical calculation and x-ray spectrum consideration. The calculation was done for Cerrobend as a common radiotherapy modifier and Mercury.Results: The values of calculated linear attenuation coefficient with this new method are in acceptable range. Also, the linear attenuation coefficient decreases slightly as the thickness of attenuating filter (Cerrobend or mercury) increased, so the procedure of linear attenuation coefficient variation is in agreement with other documents. The results showed that the attenuation ability of mercury was about 1.44 times more than Cerrobend. Conclusion: The method that was introduced in this study for linear attenuation coefficient calculation is general enough to treat beam modifiers with any shape or material by using the same formalism; however, calculating was made only for mercury and Cerrobend attenuator. On the other hand, it seems that this method is suitable for high energy shields or protector designing.
- Chang SX, Cullip TJ, Deschesne KM. Intensity modulation delivery techniques: “step & shoot” MLC auto-sequence versus the use of a modulator. Med Phys. 2000;27:948-59. doi.org/10.1118/1.598989. PubMed PMID: 10841397.
- Meyer J, Mills JA, Haas OC, Parvin EM, Burnham KJ. Some limitations in the practical delivery of intensity modulated radiation therapy. Br J Radiol. 2000;73:854-63. doi.org/10.1259/bjr.73.872.11026861. PubMed PMID: 11026861.
- du Plessis FC, Willemse CA. Monte Carlo calculation of effective attenuation coefficients for various compensator materials. Med Phys. 2003;30:2537-44. doi.org/10.1118/1.1591432. PubMed PMID: 14528976.
- Midgley SM. Materials analysis using x-ray linear attenuation coefficient measurements at four photon energies. Phys Med Biol. 2005;50:4139-57. doi.org/10.1088/0031-9155/50/17/016. PubMed PMID: 16177536.
- Lin JP, Chu TC, Liu MT. Dose compensation of the total body irradiation therapy. Appl Radiat Isot. 2001;55:623-30. doi.org/10.1016/S0969-8043(01)00129-4. PubMed PMID: 11573795.
- Tahmasebi-Birgani MJ, Seif F, Bayatiani MR. Dosimetric characteristics of mercury and cerrobend blocks in megavoltage radiation therapy. Journal of Radioanalytical and Nuclear Chemistry. 2015;303:1843-50.
- Huang PH, Chin LM, Bjarngard BE. Scattered photons produced by beam-modifying filters. Med Phys. 1986;13:57-63. doi.org/10.1118/1.595923. PubMed PMID: 3951410.
- Mejaddem Y, Hyodynmaa S, Brahme A. Photon scatter in intensity modulating filters evaluated by first Compton scatter and Monte Carlo calculations and experiments in broad beams. Phys Med Biol. 2000;45:2747-60. doi.org/10.1088/0031-9155/45/10/302. PubMed PMID: 11049169.
- Dimitriadis D, Fallone B. Compensators for intensity-modulated beams. Medical Dosimetry. 2002;27:215-20. doi.org/10.1016/S0958-3947(02)00139-5. PubMed PMID: 17592450.
- Sasaki K, Obata Y. Dosimetric characteristics of a cubic-block-piled compensator for intensity-modulated radiation therapy in the Pinnacle radiotherapy treatment planning system. J Appl Clin Med Phys. 2007;8:85-100. PubMed PMID: 17592450.
- Midgley SM. A parameterization scheme for the x-ray linear attenuation coefficient and energy absorption coefficient. Phys Med Biol. 2004;49:307-25. doi.org/10.1088/0031-9155/49/2/009. PubMed PMID: 15083673.
- Alles J, Mudde RF. Beam hardening: analytical considerations of the effective attenuation coefficient of X-ray tomography. Med Phys. 2007;34:2882-9. doi.org/10.1118/1.2742501. PubMed PMID: 17821996.
- Ali ES, Rogers DW. Functional forms for photon spectra of clinical linacs. Phys Med Biol. 2012;57:31-50. doi.org/10.1088/0031-9155/57/1/31. PubMed PMID: 22126713.
- Birgani MJT, Seif F, Chegeni N, Bayatiani MR. Determination of the effective atomic and mass numbers for mixture and compound materials in high energy photon interactions. Journal of Radioanalytical and Nuclear Chemistry. 2012;292:1367-70. doi.org/10.1007/s10967-012-1677-2.
- Chen Z, Wang X, Bortfeld T, Mohan R, Reinstein L. The influence of scatter on the design of optimized intensity modulations. Med Phys. 1995;22:1727-33. doi.org/10.1118/1.597536. PubMed PMID: 8587525.
- IAEA. Absorbed Dose Determination in Electron Beam Radiotherapy: An International Code of Practice for Dosimetry Based on Standards of Absorbed Dose to Water IAEA Technical Report Series, IAEA TRS-398; 2001.
- Johns HE. Physics of radiology: Charles River Media; 1983.
- Gürler O, Yalçın S. A practical method for calculation of mass-attenuation coefficients of β particles. Annals of Nuclear Energy. 2005;32:1918-25. doi.org/10.1016/j.anucene.2005.05.007.