In recent years several new digital mammography equipments with different innovative features have been proposed on the market [1, 2]. The work compares 7 different so called direct radiography (DR) models with respect to physical characteristics, phantom image quality and dose.

This work covers most of the innovations. It embraces 8 direct radiography (DR) systems of 7 different models and 5 different manufacturers; 2 computed radiography (CR) systems are reported for comparison (list in Fig. 2). System A1 and A2 are twin systems which underwent an x-ray tube replacement in 2010; Systems A3 and A4 are identical apart from the detector technology (Fig.3 and 4). Data of SystemD1 arepreliminary. The technological innovations introduced are related to 3 different aspects of a mammography unit, as explained in...

A. Physical characterisation: General comparison between CR and DR systems and between direct and indirect conversion technology in DR systems: Figures 1, 2 and 3 show for several systems the frequency dependence of the parameters MTF, NNPS and DQE, up to the Nyquist frequency. DR units clearly outperformed CR systems. Direct conversion flat panels (a-Se, systems A1-A4) exhibited a higher MTF than detectors based on indirect conversion with needle-like CsI (systems B1, B2) (Fig. 1). Flat panels using direct conversion technology were generally affected by...

DQE of all DR systems ranked between 55% and 80%, being higher in systems using adetectorbased on direct conversion and newer detector technology. Generally, a higher DQE traduced into a higher image quality expressed as IQFinvscore. Target/filter combinations producing spectra of higher mean energy confirmed better performances than conventional Mo/Mo ones. The innovative photoconductive switching readout exhibited a potential average dose saving of 20% compared to state of the flat panels which use conventional a-Si TFT-matrix readout. Also slit scanning acquisition showed improved image quality...

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Dr. Nadia Oberhofer Medical Physicist at Azienda Sanitaria dell'Alto Adige Ospedale di Bolzano Via L. Böhler 5 39100 Bolzano (Italy) email: [email protected] Tel. --39-0-471-907524