Using Radiochromic Films to Characterize the Dispersion of ZrO{sub 2} Nano-sized Grain Clusters in Protective Polymer Composites
Radiation dosimetry is commonly used to prevent deterministic radiation effects in high dose medical procedures. Radiochromic films find nowadays widely application in radiotherapy, interventional procedures and CT exams for isodose and maximum skin dose measurements. Moreover the size of the irradiated area and its distribution can be performed through the reading of the individual components in the RGB-spectrum. Particularly, radiochromic film has multiple advantages over alternative dosimeters for low-kV X-rays dosimetry. Concerned to spatial resolution it is far superior to that of ionization chambers and thermoluminescent dosimeters. For high energy photon fields (keV to MeV) the most used radiochromic film commercially available belongs to the EBT Gafchromic{sup R} series. On the other hand, for low energy photon fields in the x-ray range (20 kVp to 200 kVp) the best choice belongs to the XR-QA Gafchromic{sup R} film series. In this work we demonstrate the possibility of generating 2D images of thin polymeric composites films using EBT3 and XR-QA2 Gafchromic{sup R} films exposed to 6 MeV and 40 keV x-ray photons, respectively, using the digital filtering tools of the ImageJ{sup R} free software. In this context, EBT3 films were placed on the surface of a rigid anthropomorphic phantom. Then, they were covered with a thermoplastic mask made of PCL polymer. This setup was then exposed to 2.0 Gy absorbed dose in the Linear Accelerator beam. The EBT3 films were then scanned in the high resolution mode in a commercial scanner and the images subsequently treated with digital filters. It is somehow possible to see the image of the thermoplastic mask in the scanned image. However, in the treated image it is easy to observe the mask arrangement. The unexpected phenomenon here is the EB3 film ability to detect the attenuation of high energy photons by a plastic material, which in turn has a very low mass-energy attenuation coefficient, producing a very clear 2D image. This result is discussed in terms of the high Z halides added to the sensitive layer of EB3 film, once the main components are C (42.3%), H (39.7%) and O (16.0%)1-2. Based on the above results, we have speculated about the abilities of XR-AQ films in the detection of the distribution of nano-sized particles that has high mass-energy attenuation coefficients for low energy x-rays, in polymer composites. In another investigation we tested the ability of XR-QA2 Gafchromic{sup R} films to evaluate the dispersion of ZrO{sub 2} nano-sized grain clusters in protective composites. The P(VDFTrFE)/ ZrO{sub 2} film was sandwiched between two XR-QA2 radiochromic films. In this setup, one radiochromic film is directly exposed to 100 mGy of the x-rays beam and another one measures the attenuated beam. After storage for 24 hours at room temperature under no light conditions, the irradiated radiochromic films were scanned under the same conditions in order to obtain a more reliable result. All films were scanned using the same size ROI in high resolution mode and saved as tagged image file format (TIFF). The untreated scanned image of the XR-AQ2 film directed exposed to the X-ray beam and the correspondent treated image with digital filters are shown. The untreated and treated image of the XR-AQ2 film that was exposed to the attenuated x-ray beam is shown. The image treated with digital filters seems to reproduce the dispersion of ZrO{sub 2} nano-sized grain clusters in the P(VDF-TrFE) copolymer matrix. This result is also discussed in terms of the high Z halides added to the sensitive layer of XR-AQ2 film and compared to the MEV images obtained from the P(VDF-TrFE)/ZrO{sub 2} composites. The results indicate a clear correlation between the 2D radiochromic image and the MEV photography.