NUMERICAL SIGNAL TREATMENT FOR OPTIMIZED ALANINE ESR DOSIMETRY IN THETHERAPY-LEVEL DOSE RANGE/

Electron spin resonance (ESR) spectra of alanine detectors irradiated to absorbed doses below 5 Gy are affected by a varying non-linear back ground which mainly influences the lower limit of detection in alanine /ESR dosimetry. A mathematical method based on fast Fourier transform is described capable of filtering simultaneously background and noise in the frequency domain of ESR spectra. It provides clearer alanine/ES R signals down to 50 mGy. Even in non-irradiated but long-term stored alanine detectors an ESR signal could be observed similar to irradiate d alanine (pre-signal). A linear ESR signal vs absorbed dose relations hip was found above 200 mGy, after correction for background and pre-s ignal. The number of repeated ESR read-out cycles and hence the time r equired for a precise and reliable low-dose evaluation: have significa ntly been reduced. The method has been worked out for the therapy-leve l dosimetry range and tested on a Bruker ESP 300 and for comparison Br uker EMS 104 ESR spectrometer. Copyright (C) 1996 Elsevier Science Ltd