Letters to the Editor Comment on The Radiological Physics Center's standard dataset for small field size output factors (J Appl Clin Med Phys. 2012;13(5):282‐89)

The measurements were performed on Varian TrueBeam accelerators (Varian Medical Systems, Palo Alto, CA) using three different detectors all suited for small field dosimetry: a pinpoint chamber (PTW 31014; PTW, Freiburg, Germany), a prototype scintillator system developed at Technical University of Denmark, (2) and a diamond detector (PTW 60003). The measured RPC values were compared to the measured values at the participating centers with site, field size, detector type, and energy as variables. For 6 MV, the ANOVA estimated the output factors at the Danish centers to be larger than RPC data by a value of 0.0103 (about 1.2%), with a 95% confidence interval of [0.0084; 0.0123].