ALANINE/ESR DOSIMETRY FOR TOTAL BODY IRRADIATION USING ANANTHROPOMORPHIC PHANTOM

Introduction: Total Body Irradiation (TBI) is a technique widely used inthe radiation blood-oncology in the treatment of patients that need bonemarrow transplantation or peripheral stem cell transplantation.This technique has some limitations such as the lack of homogeneity ofthe dose distribution (which may show variations of 20% in the differentareas), irradiation of critical organs such as the lungs, the liver, the intestineand the eye-lens which can receive a dose comparable to that nominaland require appropriate shielding and a proper evaluation of the dose absorbedby them.The positive outcome of this type of radiation therapy is strictly relatedto a precise and accurate measurement of the distribution of the dose deliveredto the patient in the various body districts.In this work we performed an analysis by mean of Electron Spin Resonance(ESR) with alanine dosimeters of the doses absorbed in TBI treatmentby using and anthropomorphic phantom.Materials and Methods: ESR measurements were performed through theuse of commercial alanine pellets. The dosimeters were irradiated with aclinical linear accelerator for the construction of the calibration curve andthese values were used for dose calculation of the irradiation of dosimetersin an anthropomorphic phantom. Dose measurements were alsoperformed through a diode.Results: The response of alanine as function of dose is found to be linear.The alanine dose measurements in phantom were compared with thoseobtained by a diode. Estimated doses with alanine are significantly comparablewith the measurements performed with the diode. Anunderestimation of about 5% was observed with respect the doses plannedby the TPS.Conclusions: Alanine dosimetric system present several advantages suchas: tissue equivalence, linearity of its dose–response over a wide range, high stability of radiation induced free radicals, no destructive read-out procedureand these features are.