Determination of effective source to surface distance and cutout factor in small fields in electron beam radiotherapy: A comparison of different dosimeters

• Autorzy: Bayatiani Mohamad Reza , Fallahi Fatemeh , Aliasgharzadeh Akbar , Ghorbani Mahdi , Khajetash Benyamin , Seif Fatemeh

Identyfikatory

DOI

10.2478/pjmpe-2020-0028

• Języki publikacji: EN

Abstrakty

EN

Objective: The main purpose of this study is to calculate the effective source to surface distance (SSD_eff) of small and large electron fields in 10, 15, and 18 MeV energies, and to investigate the effect of SSD on the cutout factor for electron beams a linear accelerator. The accuracy of different dosimeters is also evaluated. Materials and methods: In the current study, Elekta Precise linear accelerator was used in electron beam energies of 10, 15, and 18 MeV. The measurements were performed in a PTW water phantom (model MP3-M). A Semiflex and Advanced Markus ionization chambers and a Diode E detector were used for dosimetry. SSD_eff in 100, 105, 110, 115, and 120 cm SSDs for 1.5 × 1.5 cm2 to 5 × 5 cm2 (small fields) and 6 × 6 cm2 to 20 × 20 cm2 (large fields) field sizes were obtained. The cutout factor was measured for the small fields. Results: SSDeff in small fields is highly dependent on energy and field size and increases with increasing electron beam energy and field size. For large electron fields, with some exceptions for the 20 × 20 cm2 field, this quantity also increases with energy. The SSD_eff was increased with increasing beam energy and field size for all three detectors. Conclusion: The SSD_eff varies significantly for different field sizes or cutouts. It is recommended that SSD_eff be determined for each electron beam size or cutout. Selecting an appropriate dosimetry system can have an effect in determining cutout factor.

Słowa kluczowe

EN

radiotherapy; linac; electron beam; effective SSD; cutout; dosimetry

• Wydawca: Polskie Towarzystwo Fizyki Medycznej ; De Gruyter
• Czasopismo: Polish Journal of Medical Physics and Engineering
• Rocznik: 2020
• Tom: Vol. 26, Iss. 4
• Strony: 235--242
• Opis fizyczny: Bibliogr. 20 poz., rys., tab.

Twórcy

autor

Bayatiani Mohamad Reza

• Medical Physics and Radiotherapy Department, School of Paramedical Sciences, Arak University of Medical Sciences and Ayatollah Khansari Hospital, Arak, Iran

autor

Fallahi Fatemeh

• Department of Medical Physics, School of Paramedical Sciences, Kashan University of Medical Sciences, Kashan, Iran

autor

Aliasgharzadeh Akbar

• Department of Medical Physics, School of Paramedical Sciences, Kashan University of Medical Sciences, Kashan, Iran

autor

Ghorbani Mahdi

• Biomedical Engineering and Medical Physics Department, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran

autor

Khajetash Benyamin

• Medical Physics Department, School of Medicine, Iran University of Medical Sciences, Tehran, Iran

autor

Seif Fatemeh

• Medical Physics and Radiotherapy Department, School of Paramedical Sciences, Arak University of Medical Sciences and Ayatollah Khansari Hospital, Arak, Iran

Bibliografia

• 1. ICRU. ICRU Report No. 35. Electron beams with energies between 1 and 50 MeV. ICRU, Bethesda, 1984.
• 2. Khan FM, Sewchand W, Levitt SH. Effect of air space on depth dose in electron beam therapy. Radiology 1978;126(1):249-51.
• 3. Amin MN, Heaton R, Norrlinger B, Islam MK. Small field electron beam dosimetry using MOSFET detector. J Appl Clin Med Phys 2010,12(1):50-57.
• 4. Khan FM, Doppke KP, Hogstrom KR, Kutcher GJ, Nath R, Prasad SC, et al. Clinical electron beam dosimetry: Report of AAPM Radiation Therapy Committee Task Group No. 25. Med Phys 1991;18,73-109.
• 5. Jamshidi A, Kuchnir FT, Reft CS. Determination of the source position for the electron beams from a high‐energy linear accelerator. Med Phys 1986;13(6):942-8.
• 6. Al Asmary M, Ravikumar M. Position of effective electron source for shielded electron beams from a therapeutic linear accelerator. Pol J Med Phys Engin 2010;16(1):11-21.
• 7. Shafaei Douk HS, Aghamiri MR, Ghorbani M, Farhood B, Bakhshandeh M, Hemmati HR. Accuracy evaluation of distance inverse square law in determining virtual electron source location in Siemens Primus linac. Rep Pract Oncol Radiother 2018;23(2):105-13.
• 8. Tahmasebi Birgani MJ. Zabihzadeh M, Arvandi Sh. Gharibreza E. Determining the effective source-surface distance for therapeutic electron beams. Jentashapir J Health Res 2016;7(3):30975.
• 9. Khan FM, Sewchand W, Levitt SH. Effect of air space and depth dose in electron beam therapy. Radiology 1978;126(1):249-51.
• 10. PTW The dosimetry company Available at: https://www.ptwdosimetry.com/en/support/downloads/?type=3451&downloadfile=1503. Accessed on: 6/3/2020.
• 11. Björk P, Knöös T, Nilsson P. Measurements of output factors with different detector types and Monte Carlo calculations of stoppingpower ratios for degraded electron beams. Phys Med Biol 2004;49(19):4493-506.
• 12. Hu YA, Song H, Chen Z, Zhou S, Yin FF. Evaluation of an electron Monte Carlo dose calculation algorithm for electron beam. J Appl Clin Med Phys 2008;9(3):2720.
• 13. Lief EP, Lutz WR. Determination of effective electron source size using multislit and pinhole cameras. Med Phys 2000;27:2372-5.
• 14. Roback DM, Khan FM, Gibbons JP, Sethi A. Effective SSD for electron beams as a function of energy and beam collimation. Med Phys 1995;22:2093-5
• 15. Sharma SC, Johnson MW. Electron beam effective source surface distances for a high energy linear accelerator. Med Dosim 1991;16:65-70.
• 16. Ghasemi H, Azma Z, Jabbary Arfaee A, Sadeghi M. Verification of Experimental Virtual Electron Source Position by Using Monte Carlo. Res Rev: J Pure Appl Phys 2018;6:9-16.
• 17. Papatheodorou S, Malatara G. Electron beam output of an Elekta Sli-Plus linear accelerator for irregular shaped fields and for extended SSD. Phys Med 2016;32:284-339.
• 18. Gerbi BJ, Antolak JA, Deibel FC, Followill DS, Herman MG, Higgins PD, et al. Recommendations for clinical electron beam dosimetry: supplement to the recommendations of Task Group 25. Med Phys 2009;36:3239-79.
• 19. Keivan H, Shahbazi-Gahrouei D, Shanei A. Evaluation of dosimetric characteristics of diodes and ionization chambers in small megavoltage photon field dosimetry. Int J Radiat Res 2018, 16(3): 311-321
• 20. Saidani I, Ben Salem L, Besbes M. Small field dosimetry for electron beams using four types of detectors. Phys Med 2018; 56(1):55

Uwagi

Opracowanie rekordu ze środków MNiSW, umowa Nr 461252 w ramach programu "Społeczna odpowiedzialność nauki" - moduł: Popularyzacja nauki i promocja sportu (2021).