Utilizzo di Image Plate per la dosimetria personale e ambientale

RANDACCIO, PAOLO

2013-01-01

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Abstract

Purpose: A few years ago one of the largest manufacturers of photographic dosimeters has announced the discontinuation of production of this material, so the dosimetry services have had to find an alternative. We have begun to investigate the use of material based on photostimulable phosphors entirely similar to that used in computed radiography commonly referred to as Image Plate. In order to enable the use of new dosimeters phosphors we had to characterize the material, build the systems for reading and implementing the management software. After a few years of activity, we can say that the phosphor dosimeters combine the advantages of photographic dosimetry and TLD. Methods and materials: The use of materials similar to the image plate for the dosimetry of ionizing radiation has been proposed for several years and in all experiences was highlighted the extreme sensitivity on the one hand and on the other hand that the fading is the typical problem of these materials [1]. The material we used, mainly the IP Fuji model VI, presents a fading with two decay times of the signal, there is a very rapid reduction of the signal in the early hours, then the residual signal remains at nearly constant values for very long times, this allows the use in personal and environmental dosimetry that have cycle times of the order of one or more months. For the sequential read of hundreds of dosimeters has been designed and developed a scanner that can identify each dosimeter via a barcode and then capture an image that is stored in a file in DICOM format. The dose is evaluated on the basis of a calibration performed with radiation beams of variable energy between 40 and 1250 keV. The advantage of having images easily transferable in electronic form allows users to verify the actual irradiation conditions. Results: After a period of intense activity with the phosphor dosimeters we can say that there are numerous advantages compared to the photographic dosimetry and the TLD. The new method eliminates all chemical processes for the development of films that involve physical fatigue and problems for waste collection, you get a picture in digital format which allows a better evaluation of the dose and the ease in storing and transmitting data, finally, the sensitivity of the dosimeters phosphors is so high that can be used for measuring the environmental background. Conclusion: The availability of passive dosimeters similar to image plates has made significant improvements in radiation protection, has improved the sensitivity, linear response, the dynamic range but above all it is simple to archive the dosimeter image in the form of a file in DICOM format that can be easily transmitted through the network web. References: [1] D. Mouhssine, A. Nourreddine, A. Nachab, A. Pape, F. Fernandez : A new environmental dosimeter with imaging plates for the fast neutron monitoring, Nuclear Instruments and Methods in Physics Research B 227 (2005) 609–616