DEVELOPMENT OF A LASER SCANNER FOR POLYMER GEL DOSIMETRY

Advances of the medical application of ionizing radiation, and specifically in cancer treatment, are continuously evolving and gaining higher degrees of complexity. Therefore, the ability to determine and ensure the safety and precision of these techniques must be accompanied by novel dosimetry systems. Polymer gel dosimetry is one of the new and re-markable dosimetry systems that can quantitatively record the absorbed dose and register 3D dose distributions with high resolution while maintaining tissue-equivalent properties. Typical methods used to read the recorded signal in a polymer gel dosimeter, such as magnetic resonance imaging, X-ray tomography, and ultrasound-based techniques in-clude complex and expensive instruments. On the other hand, there are low-cost alternatives like optical methods that can be optimized and designed for the study of polymer gel dosimetry. The objective of this study is to present the de-sign, construction, development, and characterization of a low-cost laser scanner for bi-dimensional PGD analysis. With this equipment, characterization and optimization assays were performed on typical samples, and compared to those obtained by commercial or validated instruments with similar results, proving the capacity of the designed instrument as a reading tool for polymeric gel dosimetry.

DEVELOPMENT OF POLYMERIC MATERIALS FOR X-RAY DOSIMETRY WITH ENHANCED OPTICAL SENSIBILITY

The use of a new reagent with the capacity of forming colored organo-metallic complexes with metal ions is herein studied for its application in X-Ray dosimetry, aiming to assess its effect on the dose-sensitivity of polymer gel dosimetry. The improvement of the sensitivity of polymeric dosimeters, commonly used to quantitatively register dose distribution in radiotherapy, requires considering both the intrinsic mechanism involved in the irradiation of the dosimetry system (polymerization) and the selected readout technique (e.g. spectroscopy techniques). One of the most used readout methods is measuring the change in the optical density of the dosimeters after their irradiation. The formulation of a new sensitive material able to form organo-metallic complexes and the potentiality of achieving significant changes in the optical density in the irradiated region is studied in this work. For this purpose, a new monomer (GMA-IDA) was synthesized and used in the polymerization with other monomers, commonly employed in polymer gel dosimetry (acrylamide, N,N’-methylenebisacrylamide y N-isopropilacrylamide. The polymerization of the new sensitive material was initiated by a redox reaction (APS/TEMED) or by ionizing radiation (X-Rays), then the effect of the new monomer over the performance of the dosimetry material was evaluated. Results indicated that the new formed polymer has the capacity of forming colored complexes with Cu2+.