ALANINE/ESR DOSIMETRY FOR TOTAL BODY IRRADIATION USING AN ANTHROPOMORPHIC PHANTOM

Abstract

Introduction: Total Body Irradiation (TBI) is a technique widely used in the radiation blood-oncology in the treatment of patients that need bone marrow transplantation or peripheral stem cell transplantation. This technique has some limitations such as the lack of homogeneity of the dose distribution (which may show variations of 20% in the different areas), irradiation of critical organs such as the lungs, the liver, the intestine and the eye-lens which can receive a dose comparable to that nominal and require appropriate shielding and a proper evaluation of the dose absorbed by them. The positive outcome of this type of radiation therapy is strictly related to a precise and accurate measurement of the distribution of the dose delivered to 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 treatment by using and anthropomorphic phantom. Materials and Methods: ESR measurements were performed through the use of commercial alanine pellets. The dosimeters were irradiated with a clinical linear accelerator for the construction of the calibration curve and these values were used for dose calculation of the irradiation of dosimeters in an anthropomorphic phantom. Dose measurements were also performed 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 those obtained by a diode. Estimated doses with alanine are significantly comparable with the measurements performed with the diode. An underestimation of about 5% was observed with respect the doses planned by the TPS. Conclusions: Alanine dosimetric system present several advantages such as: tissue equivalence, linearity of its dose–response over a wide range, high stability of radiation induced free radicals, no destructive read-out procedure and these features are.