The response of alanine to a 150Â keV X-ray beam

The alanine/electron paramagnetic resonance (EPR) dosimetry system was used to measure a 150 keV X-ray quality, and the response was compared to 60Co γ-ray measurements using the same system. The absorbed dose-to-alanine per unit air-kerma for the two beam qualities were calculated with the EGSnrc Monte Carlo code. The measured and calculated results were combined to derive the relationship of the alanine/EPR response to the absorbed dose-to-alanine. We found a 16.1% (±0.8) reduction in alanine/EPR response to air-kerma for the 150 keV X-rays relative to the 60Co γ-rays, and a 5.7% (±0.8) reduction in alanine/EPR response to the absorbed dose-to-alanine. The results support an earlier published prediction.