Dosimetric evaluation and comparation of TL responses of LiF:Mg,Ti and mu LiF:Mg,Ti in the clinical electron beams dosimetry applied to total skin irradiation (TSEB) treatments

摘要

The Total Skin Electron Beam (TSEB) irradiation is a radiotherapeutic technique that aims to provide the patient's skin surface with a more homogeneous dose, in order to treat cutaneous T-cell lymphomas, both for curative and palliative purposes. Electron irradiation penetrates a few millimeters into the skin, reaching the affected parts completely, without penetrating the internal organs. In vivo dosimetry has become an important role for the treatment of total skin irradiation within a rigorous quality assurance program that should be an integral part of the radiotherapy departments. The use of TLDs in vivo can identify variations in the prescribed dose because its measurement accuracy and great precision. The LiF:Mg,Ti is the most used TL material and widely studied in radiotherapy dosimetry due to near tissue-equivalence of the material, along with its overall reliability. The dosimeters of mu LiF:Mg,Ti have been gaining considerable importance in the radiotherapy departments. These detectors allow measurements in vivo with great advantages due to their minimum dimensions of 1 x 1 x 1 mm(3). This paper reports a comparative study of the TL responses of both materials to dose evaluation in TSEB treatments. The TL response of both materials in several TSEB parameter tests and in clinical application were evaluated, analyzing the dose distribution in a treatment simulation using AldersonRando anthropomorphic phantom. The results showed that the mu LiF:Mg,Ti presented greater variation of the response in relation to LiF dosemeters in some parameters analyzed, due to the small dimensions and to evaluate doses absorbed in the surface over a large area in the treatment plan.