High-sensitivity radiation detector for low dose levels radiological applications

MAURO VALENTE; WLADIMIR MOLINA

MONTEVIDEO

Congreso; X - LATIN AMERICAN SYMPOSIUM OF NUCLEAR PHYSICS AND APPLICATIONS; 2013

COM LATINOAMERICANA DE FISICA - JEFFERSON LAB USA - UNIV. REPUBLICA URUGUAY

Radiation dosimetry by Fricke gel was largely used, generally focused and optimized forradiotherapy applications therefore involving relative high dose levels [1]. Many relevantadvantages, like linear response, being dose rate and LET almost independent, tissue-equivalence and mainly continuous 3D dose mapping, suggest that its adaptation to lowdoser level radiological applications might constitute a valuable tool.This work presents the characterization and performance of a novel dosimeter basedon Fricke solution optimized for low dose levels [2]. Several chemical composition werestudied to achieve satisfactory response for low dose levels, obtaing a modified Frickesolution consisting of suitable sulphuric acid, ferrous sulphate, Xylenol orange and ben-zoic acid concentrations that were optimized for assessing high sensitivity at low doselevels. Sample in standard spectrophotometric vials were irradiated with X-ray beamsinside water-equivalent phantoms. solid-state CdTe detector was used to characterisizeradiation quality; whereas calibrated ionization chamber was used as reference to mea-sure dose rates. Samples were analyzed by light transmission and absorbance before andafter irradiation. Sensitivity for low dose levels was significantly improved by the devel-oped system, which was benchmarked using typical setups for conventional radiography.Dosimeter vials were placed inside a water-equivalent phantom exposed to kilovoltage X-ray beam imaged (using long acquisition times) with a bi-dimensional digital detector, theintegral beam line at Laboratorio de Investigaciones e Instrumentaci ́on en F ́ısica Aplicadaa la Medicina e Im ́agenes por Rayos X (LIIFAMIRX ), as it is customary in radiology.Comparisons of dose values between Fricke gel dosimeter, ionization chamber and MonteCarlo simulations were performed for complex digital radiography setups. It should beremarked that the proposed method exhibits satisfactory reliability and high performancesuggesting its potentiality as a promising low-level dosimetry system.[1] M. Valente, Fricke gel dosimetry for 3D imaging of absorbed dose in radiotherapyPhD. thesis. University of Milan, Italy (2007)[2] W. Molina, Desarrollo y caracterizaci ́on de un sistema de Fricke gel para dosimetr ́ıaen radiodiagn ́ostico MSc. thesis. IVIC, Venezuela (2013)