On site evaluation of three flat panel detectors for digital radiography

Giovanni Borasi, Andrea Nitrosi, Paolo Ferrari, Davide Tassoni

Research output: Contribution to journalArticle

Abstract

During a tender we evaluated the image performance of three commercially available active matrix flat panel imagers (AMFPI) for general radiography, one based on direct detection method (Se photoconductor) the other two on indirect detection method (CsI phosphor). Basic image quality parameters (MTF, NNPS, DQE) were evaluated with particular attention to dose and energy dependence. As it is known, presampling modulation transfer function (MTF) of selenium based detector is very high (at 70 kV, 2 cycles/mm, 2.5 μGy, about 0.80). Indirect detection panels exhibit a comparable (lower) resolution (at 70 kV, 2 cycles/mm, 2.5 μGy, MTF is about 0.34 for both the systems analyzed) and a more pronounced energy and dose dependence could also be noted in one of them. As a consequence of the very high resolution, the normalized noise power spectrum (NNPS) of the direct system is substantially flat, very similar to a white noise. Considering that the sensitive layer of all detectors is the same (0.5 mm), the relatively higher NNPS values are related to selenium absorption properties (lower Z respect to CsI:T1) and detector inherent noise. NNPSs of the other systems, at low frequencies, are comparable but the frequency dependence is significantly different. At 70 kV, 2.5 μGy, 0.5 cycles/mm detective quantum efficiency (DQE) is about 0.35 for the direct detection system, and about the same (0.6) for the indirect ones. The combined effect of additive and multiplicative noise components makes DQE dependence on dose not monotonic. DQE present a maximum for an intermediate exposure. This complex behavior may be useful to characterize the systems in terms of the monodimensional integral over the frequency of DQE (IDQE). Both visual contrast-detail experiment and the direct evaluation of the signal-to-noise ratio confirmed, at least in a qualitative way, the system performances predicted by IDQE.

Original languageEnglish
Pages (from-to)1719-1731
Number of pages13
JournalMedical Physics
Volume30
Issue number7
DOIs
Publication statusPublished - Jul 1 2003

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Radiographic Image Enhancement
Selenium
Noise
Signal-To-Noise Ratio
Radiography

ASJC Scopus subject areas

  • Biophysics

Cite this

Borasi, G., Nitrosi, A., Ferrari, P., & Tassoni, D. (2003). On site evaluation of three flat panel detectors for digital radiography. Medical Physics, 30(7), 1719-1731. https://doi.org/10.1118/1.1569273

On site evaluation of three flat panel detectors for digital radiography. / Borasi, Giovanni; Nitrosi, Andrea; Ferrari, Paolo; Tassoni, Davide.

In: Medical Physics, Vol. 30, No. 7, 01.07.2003, p. 1719-1731.

Research output: Contribution to journalArticle

Borasi, G, Nitrosi, A, Ferrari, P & Tassoni, D 2003, 'On site evaluation of three flat panel detectors for digital radiography', Medical Physics, vol. 30, no. 7, pp. 1719-1731. https://doi.org/10.1118/1.1569273
Borasi, Giovanni ; Nitrosi, Andrea ; Ferrari, Paolo ; Tassoni, Davide. / On site evaluation of three flat panel detectors for digital radiography. In: Medical Physics. 2003 ; Vol. 30, No. 7. pp. 1719-1731.
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