Optical analysis of gel dosimeters : comparison of Fricke and normoxic polymer gels

The dosimetry method based on optical analysis of gel layers has been experienced utilising both Fricke and polymer (normoxic) gels. The aim of the work was that of investigating the potentiality of a normoxic polymer gel and of performing a further verification of the reliability of Fricke gel dosimeters. Optical absorbance was measured, both with a spectrophotometer and by imaging light transmittance detected with a CCD camera. The results of the study of sensitivity, linearity of the response and reproducibility of the polymer gel dosimeter have shown acceptable performances, except for doses below 2 Gy. The linearity range extends up to 20 Gy. On the other side, dose images and profiles have shown noticeable differences when compared to those calculated or measured with ionisation chambers or Fricke gel dosimeters. Such Fricke dosimeters have given further confirmation of their reliability.