The effect of external wedge on the photoneutron dose equivalent at a high energy medical linac

• Autorzy: Hashemi , S. M. , Raisali G. , Taheri M. , Majdabadi A. , Ghafoori M.
• Języki publikacji: EN

Abstrakty

EN

Medical linacs used in radiotherapy produce bremsstrahlung spectra. In the energy range from 8 to 25 MV medical linacs produce, besides the clinically useful electron and photon beams, secondary neutrons. The aim of this study was to investigate the effect of an external wedge filter on the photoneutron dose equivalent produced by a medical linac at patient plane. Polycarbonate (PC) films were used for the determination of photoneutron dose equivalent produced by a Varian 2100 C/D linac working at 18 MV photon mode. Neutron dose equivalent was measured at distances 0, 10, 20 and 50 cm from the center of the X-ray beam for open field and after inserting a wedge filter. It was noted that by inserting the external wedge in the path of the X-ray beam, the photoneutron dose equivalent was increased compared to open field. It can be concluded that an external wedge, made from heavy materials may act like the other components of linac head, producing undesired photoneutrons and thus increasing patient dose.

Słowa kluczowe

EN

photoneutron; linac; polycarbonate (PC); external wedge; radiotherapy

• Wydawca: Institute of Nuclear Chemistry and Technology
• Czasopismo: Nukleonika
• Rocznik: 2011
• Tom: Vol. 56, No. 1
• Strony: 49--51
• Opis fizyczny: Bibliogr. 12 poz., rys.

Twórcy

autor

Hashemi , S. M.

autor

Raisali G.

autor

Taheri M.

autor

Majdabadi A.

autor

Ghafoori M.

• Dosimetry and Radiation Monitoring Research Group, Agricultural, Medical and Industrial Research School (AMIRS), Nuclear Science and Technology Research Institute (NSTRI), P. O. Box 31485-49, Karaj, Tehran, Iran, Tel.: [phone], Fax: +98 2,

Bibliografia

• 1. d’Errico F, Nath R, Tana L, Corzio G, Alberts WG (1997) In-phantom dosimetry and spectrometry of photoneutrons from an 18 MeV linear accelerator. Med Phys 25:1717–1724
• 2. Followill DS, Stoval MS, Kry SF, Ibbott GS (2003) Neutron source strength measurements for Varian 2100 C/D, Siemens, Elekta and General Electric linear accelerator. J Appl Clin Med Phys 4:189–194
• 3. Hall EJ, Martin SG, Amols H, Hei TK (1995) Photoneutron from medical linear accelerators – radiobiological measurements and risk estimates. Int J Radiat Oncol Biol Phys 33;1:222–230
• 4. Hashemi SM, Hashemi-Malayeri B, Raisali G et al. (2008) Measurement of photoneutron dose produced by wedge filters of a high energy linac using polycarbonate films. J Radiat Res 49;3:279–283
• 5. Hasib GM, Piesch E (1978) Improvement of the ECE technique for fast neutron dosimetry (personal neutron dosimetry DOE workshop London). Richland, WA report PNL-2807, Battle Pacific Northwest Labs
• 6. IAEA (2001) 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
• 7. IAEA (2001) Compendium of neutron spectra and detector responses for radiation protection purposes. Supplement to Technical Reports Series no. 318. International Atomic Energy Agency, Vienna
• 8. ICRP (1990) ICRP recommendations, ICRP Report no. 60. International Commission on Radiological Protection, Stockholm, Sweden
• 9. NCRP (1984) Neutron contamination from medical accelerators. NCRP Report no. 79. National Council on Radiation Protection and Measurements, Washington DC, USA
• 10. Ongaro C, Zanini A, Nastasi U, Ródenas J, Ottaviano G, Manfredotti C (2000) Analysis of photoneutron spectra produced in medical accelerators. Phys Med Biol 45:L55–L61
• 11. Sohrabi M, Mostofizadeh A (1999) Measurement of photoneutron dose in and out of high energy X-ray beam of a Saturne 20 medical linear accelerator by ECE polycarbonate detectors. Radiat Meas 31:479–482
• 12.Taheri M, Hosseini Toudeshki S (2005) Characteristic studies for fast detection of a wide energy range of alpha particles in polycarbonate detectors. Radiat Meas 40:307–310