Novel tissue-equivalent chemical dosimeter optimized for radiological low dose levels

M. VALENTE; W. MOLINA; G. TIRAO; D. GRAÑA; F. MALANO; P. PEREZ

Lyon

Conferencia; 11th International Lowrad Conference; 2012

Fricke gel dosimeters were largely used to radiation dosimetry during the last decades. However, this type of dosimeters were generally optimized for their employment In radiotherapy applications therefore focused on relative high dose levels. Due to some relevant advantages, like tissue-equivalence, linear response, quasi LET and dose rate independence and continuous 3D dose mapping capability; it would be desirable to adapt this technique for low dose level applications, like radiological practices. This work presents the characterization and preliminary performance of a novel dosimeter based on Fricke solution that has been optimized for low dose levels.Several chemical composition were studied in order to achieve a good enough dosimeter response for low dose levels and among these the selected one was a modified Fricke solution fixed to a gel matrix containing benzoic acid. Particularly, sulphuric acid, ferrous sulphate, Xylenol orange and benzoic acid concentrations were optimized for assessing high sensitivity at low dose levels.Dosimeter sample were prepared in standard spectrophotometric vials and they were irradiated with X-ray beams from conventional X-ray tubes. Samples were irradiated inside cylindrical (40mm height and diameter) water-equivalent phantoms at 100cm from the source. Farmer type calibrated ionization chamber was used as reference to measure dose rates inside phantoms corresponding to vials locations. Solid-state CdTe detector was used to measure source radiation quality, like flux rate and emission spectrum.Dosimeter vials were analyzed measuring visible light transmission and absorbance before and after irradiation. After dosimeter composition optimization, the dose-response curve showed significant improvement regarding the sensitivity for low dose levels.