DOI QR코드

DOI QR Code

Dosimetric Characteristics of 6 MV Modified Beams by Physical Wedges of a Siemens Linear Accelerator

  • Zabihzadeh, Mansour (Department of Medical Physics, Faculty of Medicine, Ahvaz Jundishapur University of Medical Sciences) ;
  • Birgani, Mohammad Javad Tahmasebi (Department of Medical Physics, Faculty of Medicine, Ahvaz Jundishapur University of Medical Sciences) ;
  • Hoseini-Ghahfarokhi, Mojtaba (Department of Medical Physics, Faculty of Medicine, Ahvaz Jundishapur University of Medical Sciences) ;
  • Arvandi, Sholeh (Departments of Clinical Oncology, Golestan Hospital) ;
  • Hoseini, Seyed Mohammad (Departments of Clinical Oncology, Golestan Hospital) ;
  • Fadaei, Mahbube (Department of Medical Physics, Faculty of Medicine, Ahvaz Jundishapur University of Medical Sciences)
  • Published : 2016.06.01

Abstract

Physical wedges still can be used as missing tissue compensators or filters to alter the shape of isodose curves in a target volume to reach an optimal radiotherapy plan without creating a hotspot. The aim of this study was to investigate the dosimetric properties of physical wedges filters such as off-axis photon fluence, photon spectrum, output factor and half value layer. The photon beam quality of a 6 MV Primus Siemens modified by 150 and 450 physical wedges was studied with BEAMnrc Monte Carlo (MC) code. The calculated present depth dose and dose profile curves for open and wedged photon beam were in good agreement with the measurements. Increase of wedge angle increased the beam hardening and this effect was more pronounced at the heal region. Using such an accurate MC model to determine of wedge factors and implementation of it as a calculation algorithm in the future treatment planning systems is recommended.

Keywords

Beam hardening;Monte Carlo calculation;physical wedge filter;radiotherapy

References

  1. Ahmad M, Hussain A, Muhammad W, et al (2010). Studying wedge factors and beam profiles for physical and enhanced dynamic wedges. J Med Physics, 35, 33-41. https://doi.org/10.4103/0971-6203.57116
  2. Andreo P, Burns DT, Hohlfeld K, et al (2000). IAEA ,TRS-398: Absorbed dose determination in external beam radiotherapy: An International code of practice for dosimetry based on standards of absorbed dose to water. IAEA: international atomic energy agency. Vienna, 10, 46-80.
  3. Attalla EM, Abo-Elenein HS, Ammar H, et al (2010). Comparison of dosimetric characteristics of Siemens virtual and physical wedges for ONCOR linear accelerator. J Med Physics, 35, 164-9. https://doi.org/10.4103/0971-6203.62137
  4. Geraily GH, Mirzapour M, Mahdavi S.R, et al (2014). Monte Carlo study on beam hardening effect of physical wedges. Int J Radiat Res, 12, 249-56.
  5. Hubbell JH, Seltzer SM (1995). Tables of x-ray mass attenuation coefficients and mass energy absorbtion coefficients from 1 keV to 20 keV for elements Z=1 to 92 and 48 additional substances of dosimetric interest. NISTIR, 5632.
  6. IAEA, report: TRS-398 (2000). Absorbed dose determination in external beam radiotherapy. Veina, International atomic energy agency.
  7. ICRU: Report -50 (1993). Prescribing, recording and reporting photon beam therapy. Bethesda, MD: International Commission on Radiation Units and Measurements.
  8. Kowalik A, Litoborski M (2013). Multienergetic verification of dynamic wedge angles in medical accelerators using multichannel linear array. Reports Practical Oncol Radiotherapy, 18, 220-34. https://doi.org/10.1016/j.rpor.2013.04.029
  9. Miften M, Zhu XR, Takahashi K, et al (2000). Implementation and verification of virtual wedge in a three-dimensional radiotherapy planning system. Med Physics, 27, 1635-43. https://doi.org/10.1118/1.599030
  10. Muhammad W, Maqbool M, Shahid M, et al (2011). Assessment of computerized treatment planning system accuracy in calculating wedge factors of physical wedged fields for 6 MV photon beams. Physica Med, 27, 135-43. https://doi.org/10.1016/j.ejmp.2010.06.003
  11. Muren LP, Hafslund R, Gustafsson A, et al (2001). Partially wedged beams improve radiotherapy treatment of urinary bladder cancer. Radiotherapy Oncol, 59, 21-30. https://doi.org/10.1016/S0167-8140(00)00337-6
  12. Njeh CF (2015). Enhanced dynamic wedge output factors for Varian 2300CD and the case for a reference database. J Applied Clinical Med Physics, 16, 5498.
  13. Petrovic B, Grzadziel A, Rutonjski L, et al (2010). Linear array measurements of enhanced dynamic wedge and treatment planning system (TPS) calculation for 15 MV photon beam and comparison with electronic portal imaging device (EPID) measurements. Radiol Oncol, 44, 199-206.
  14. Rogers DWO, Ma C-M, Walters B, et al (2003). BEAMnrc User Manual. NRCC Report PIRS-509 (National Research Council of Canada), Ottawa, Ontario, Canada.
  15. Shih R, Li XA, Chu JC (2001). Dynamic wedge versus physical wedge: a Monte Carlo study. Medical Physics, 28, 612-9. https://doi.org/10.1118/1.1359249
  16. Verhaegen F, Das IJ (1999). Monte Carlo modelling of a virtual wedge. Physics Med Biol, 44, 251-9. https://doi.org/10.1088/0031-9155/44/12/402
  17. Vinagre FL, Simoes PC, Rachinhas PJ (2009). Omni-wedge technique for increased dose homogeneity in head and neck radiotherapy. Physica Med, 25, 154-9. https://doi.org/10.1016/j.ejmp.2009.02.002
  18. Zhu XR, Gillin MT, Jursinic PA, et al (2000). Comparison of dosimetric characteristics of Siemens virtual and physical wedges. Medical Physics, 27, 2267-77. https://doi.org/10.1118/1.1312813