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Proceedings Paper

Physical characteristics of a clinical prototype for full-field digital mammography with an a-Se flat-panel detector
Author(s): Barbara Lazzari; Giacomo Belli; Cesare Gori; Kirsi Nykanen
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Paper Abstract

The purpose of this study was to evaluate physical characteristics of a clinical prototype for full-field digital mammography (FFDM) with an amorphous selenium (a-Se) flat-panel detector (FPD) and to compare these results with the currently available systems for FFDM. The effective FPD area consists of 2816 x 2016 pixel matrix having a pixel pitch of 85μm. This yields to theoretical maximum spatial frequency of ~5.9lp/mm. The basic performance of Instrumentarium clinical prototype direct mammography system has been assessed on the basis of measured response curve, the modulation transfer function (MTF), the noise power spectrum (NPS), the noise equivalent quanta (NEQ) and the detective quantum efficiency (DQE) in the clinical setting. The system shows a linear response curve over a dynamic range from 0.4 mR to 57 mR. The presampling MTF was found to be approximately 0.91, 0.72 and 0.50 at 2, 4 and 5.9 (Nyquist frequency) lp/mm. The NEQ is linearly related to the exposure starting from about 8 mR above which value the system can be considered noise quantum limited. The DQE, evaluated in clinical conditions (28kVp Mo-Mo spectrum hardened by 4cm of PMMA) is at close to zero spatial frequency approximately 69% at 46.4 mR and 61% at 8.3 mR. Below 8 mR the DQE(0) falls to 54.4%, 46% and 32.5% at 5.2, 3.0 and 1.4 mR respectively due to structured and electronic noise. The results of quantitative analysis demonstrate a high MTF as we expected due to direct conversion technology and a high DQE over the exposure range from 8 mR to 50 mR. The NEQ shows that the system can be considered noise quantum limited above 8 mR suggesting the exposure level that should be set in the clinical practice to ensure an adequate image quality.

Paper Details

Date Published: 5 June 2003
PDF: 11 pages
Proc. SPIE 5030, Medical Imaging 2003: Physics of Medical Imaging, (5 June 2003); doi: 10.1117/12.479989
Show Author Affiliations
Barbara Lazzari, Univ. General Hospital of Careggi (Italy)
Giacomo Belli, Univ. General Hospital of Careggi (Italy)
Cesare Gori, Univ. General Hospital of Careggi (Italy)
Kirsi Nykanen, Instrumentarium Corp. (Finland)


Published in SPIE Proceedings Vol. 5030:
Medical Imaging 2003: Physics of Medical Imaging
Martin J. Yaffe; Larry E. Antonuk, Editor(s)

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