Characterisation of a commercial flatbed scanner for external beam dose verification using EBT gafchromic and EDR2 films

Objective: The goal of this study was to evaluate the performance of an inexpensive Epson Perfection V700 flatbed scanner for film dosimetry. The scanner was tested with EBT Gafchromic and Kodak EDR2 films and compared with a Vidar VXR-16 Dosimetry Pro scanner - the recognized standard for film dosimetry. Material and Methods: Measurements were made at the CHUV in Lausanne and Clinique de Genolier in Genolier. Planar dose distributions with doses in the range 0.1 to 3.5 Gy were delivered to the EBT Gafchromic and EDR2 films in a solid water phantom. Sensitometric curves were determined for each scanner-film combination and then IMRT and percentage depth dose measurements were made. Results: The uniformity of the scanner response is discussed for the two films and both scanners. Differences in percentage depth dose measurements and sensitometric curves for the two films and scanners are shown. The limitations of each scanner for EBT Gafchromic or EDR2 film dosimetry are described. Conclusion: An inexpensive Epson Perfection V700 flatbed scanner can be used for EBT Gafchromic film dosimetry, for example for verifying planar dose distributions for individual patient IMRT QA

Comparaison des performances de deux systemes TEP/TDM corps entier selon la norme NEMA NU 2-2001

Resume L'objectif du travail etait la caracterisation de deux installations TEP/TDM, basees sur des technologies differentes, sur la base du protocole propose dans la norme NEMA NU 2-2001. Les deux systemes ont ete qualifies en mode d'acquisition 3D en utilisant les fantomes de la National Electric Manufacturers Association (NEMA). Les resultats obtenus montrent que la norme NEMA permet de mettre en evidence des differences entre la resolution spatiale, la sensibilite, la fraction de diffuse et les performances en taux de comptage des deux systemes, differences attribuables a la geometrie et aux materiaux des detecteurs utilises. Ainsi, l'utilisation de la norme permet d'etablir de veritables points de reference des systemes. Les tests de qualite d'image, obtenus dans des conditions plus proches des applications cliniques montrent que les deux installations, en depit de leurs differences de technologies, produisent, dans des temps d'acquisition courts, des images suffisamment contrastees pour permettre la detection de petites lesions. Ce test devrait d'ailleurs faire partie des tests de stabilite pour assurer la comparaison des examens, lorsque les aspects quantitatifs sont d'importance. The goal of work is the characterization of two PET/CT units that are based on different technologies, using the methodology proposed in the NEMA NU 2-2001 standard. The two systems were qualified in the 3D acquisition mode by means of the National Electric Manufacturers Association (NEMA) phantoms. The results obtained showed that the NEMA standard allows to highlight differences in terms of spatial resolution, sensitivity, scatter fraction and counting rate performances between the two systems ; differences that can be explained by the geometry of the units and the materials of the detectors used. Thus, the use of the standard makes it possible to benchmark PET units and establish reference values that can be used to follow the stability of the system over the time. The tests of image quality, obtained under conditions closer to the clinical applications, showed nevertheless that the two units give, in spite of different technologies, images with sufficient contrast, within short acquisition times, allowing the detection of small lesions. This test should be part of the constancy tests to enable the comparison of examinations performed on different units when the quantitative aspects are of importance