Establishment of a  Reference High-Energy Electron Beam

Solimanian, A; Derikum, K

Establishment of a Reference High-Energy Electron Beam

Document Type : Research Paper

Authors

A Solimanian

K Derikum

Abstract

Dosimetry of ionizing radiations are based on standard methods issued by competent national and international organizations. Establishment of reference radiations at standard dosimetry laboratories are essential to transfer measurement standards to radiation users. This paper presents attempts made at Ionizing Radiation Division of PTB to produce a reference 20 MeV electron beam based on the German standard DIN 6800-2. The quality of the 20 MeV electron beam of a Philips SL75-20 linear accelerator (linac) is determined by a well designed plane-parallel ionization chamber, in terms of mean energy of the electron beam at the surface of a water phantom. Three types of cylindrical ionization chambers are calibrated against the primary standard of absorbed dose to water at PTB in Co-60 gamma radiation. Based on DIN 6800-2, independent measurements of absorbed dose to water are then carried out by these three calibrated chambers at a reference depth in water phantom and with reference to the dose monitoring system of the linac which consists of two other ionization chambers located in water phantom. The results are compared and a mean calibration factor for the monitor chambers with a combined standard uncertainty is determined.

Highlights

1. Irternational Atomic Energy Agency, “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, IAEA,Vienna (2000).

2. DEUTSCHES INSTITUT FUR NORMUNG, “Dosismeβverfahren nach der Sondenmethode für Photonen- und Elektronenstrahlung, Teil 2: Ionisationsdosimetrie,” Deutsche Norm DIN 6800-2, DIN, Berlin (1997).

3. American Association of Physicists in Medicine (AAPM), Task Group 51: Protocol for Clinical Reference Dosimetry of High-Energy Photon and Electron Beams, Med. Phys. 26, 1847-1870 (1999).

4. H. Feist, “Determination of absorbed dose to water for high energy photons and electrons by total absoption of electrons in ferrous sulphate solution,” Phys. Med. Biol. 27, 1435-1447 (1982).

5. ع. سلیمانیان و همکاران، ”دزیمتری باریکه‌های فوتون و الکترون در پرتودرمانی براساس استانداردهای دُز جذبی آب،“ نشریة علمی سازمان انرژی اتمی ایران، شمارة 23، 16-1، (1380).

Keywords

reference electron beam

beam quality

ionisation chamber

calibration

absorbed dose

2. DEUTSCHES INSTITUT FUR NORMUNG, “Dosismeβverfahren nach der Sondenmethode für Photonen- und Elektronenstrahlung, Teil 2: Ionisationsdosimetrie,” Deutsche Norm DIN 6800-2, DIN, Berlin (1997).

3. American Association of Physicists in Medicine (AAPM), Task Group 51: Protocol for Clinical Reference Dosimetry of High-Energy Photon and Electron Beams, Med. Phys. 26, 1847-1870 (1999).

4. H. Feist, “Determination of absorbed dose to water for high energy photons and electrons by total absoption of electrons in ferrous sulphate solution,” Phys. Med. Biol. 27, 1435-1447 (1982).