Verification of treatment plans for skin cancer in brachytherapy with the use of TLD technique

Abstract

Introduction Thermoluminescent detectors (TLDs), especially those made of LiF phosphor doped with magnesium and titanium (LiF:Mg,Ti) are widely used in dosimetric methods for ionizing radiation measurements. Purpose Dosimetric system in vivo in brachytherapy is less developed than that for teletherapy due the fact that not all detectors are able to register low-energy photons emitted from radioactive isotopes sources used in brachytherapy. A detector which satisfies requirements presented in the AAPM Task Group no. 43 report from 2004 and is recommended in the report is TLD-100. This kind of detector was used in presented studies. Materials and methods Dose measurements were performed in selected individual skin cancer cases localized in the head-and neck and pelvis areas. All treatment plans were performed in the Abacus 3.2 Varian Medical Systems for brachytherapy HDR. Each patient obtained his individual mask built from polymer clay, Wood’s alloy or Orfit material. Prior to the patient’s irradiation all treatment plans were verified with TL-100 detectors placed in situ at particular places of the individual masks for each cancer case. Results Dose verifications were performed for defined stops of the radioactive 192Ir source for 10 selected treatment plans. The highest spread of doses was equal to 0,7% while the acceptable difference between the planed and measured doses in clinical dosimetry is Conclusion TL detector is a good tool for treatment plans verifications and quick detection of possible mistakes in brachytherapy.