Improvement of sensitivity in the alanine/ESR dosimetry

Improvement of sensitivity in the alanine/ESR dosimetry is presented by considering spin-lattice and spin-spin relaxation rates of the room temperature radical in irradiated polycrystalline image-alanine. Both relaxation rates exhibit anomalous decrease due to hindered rotation of the methyl group. It is demonstrated that this effect can improve a signal: noise ratio of the spectrum for 30% by detecting the ESR signal at around 200 K compared to the room temperature detection. The application of improvement can be expected in the therapy-level dose range where the intensity of detected signal is comparable to a nonlinear background signal.