Response of the alanine/ESR dosimetry system to MV X-rays relative to (60)Co radiation.

The measurand relevant in dosimetry for radiation therapy is the absorbed dose to water, D(W). The Physikalisch-Technische Bundesanstalt (PTB) has established a secondary standard for D(W) for high-energy photon and electron radiation based on electron spin resonance (ESR) of the amino acid alanine. Since the calibration is usually performed using (60)Co radiation while a huge part of the external radiation therapy is done with high-energy x-rays from linear accelerators, determination of the response is an important issue.