Comparison of Dw measurements by alanine and synthetic diamond dosimeters in photon beams with 1 cm * 1 cm field size

For photon beam sizes lower than 2 cm * 2 cm no absorbed-dose-to-water (Dw) primary standards are available for determining the possible influence of field size on the dosimeter response. In this work, Dw measurements performed in 1 cm * 1 cm photon beams at PTB using alanine and synthetic diamond dosimeters were compared in order to assess the reliability of the two dosimetric systems in such a small field size. The ratio of Dw values measured by diamond dosimeters to Dw values measured by alanine was 0.991 ± 1.5% (1 SD) and 1.007 ± 1.3% (1 SD) for 6 MV and 10 MV photon beams, respectively. This shows that both systems are capable of accurately measuring Dw in small fields. (authors)