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Proceedings Paper

Digital mammography--DQE versus optimized image quality in clinical environment: an on site study
Author(s): Nadia Oberhofer; Alessandro Fracchetti; Margareth Springeth; Ehrenfried Moroder
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Paper Abstract

The intrinsic quality of the detection system of 7 different digital mammography units (5 direct radiography DR; 2 computed radiography CR), expressed by DQE, has been compared with their image quality/dose performances in clinical use. DQE measurements followed IEC 62220-1-2 using a tungsten test object for MTF determination. For image quality assessment two different methods have been applied: 1) measurement of contrast to noise ratio (CNR) according to the European guidelines and 2) contrast-detail (CD) evaluation. The latter was carried out with the phantom CDMAM ver. 3.4 and the commercial software CDMAM Analyser ver. 1.1 (both Artinis) for automated image analysis. The overall image quality index IQFinv proposed by the software has been validated. Correspondence between the two methods has been shown figuring out a linear correlation between CNR and IQFinv. All systems were optimized with respect to image quality and average glandular dose (AGD) within the constraints of automatic exposure control (AEC). For each equipment, a good image quality level was defined by means of CD analysis, and the corresponding CNR value considered as target value. The goal was to achieve for different PMMA-phantom thicknesses constant image quality, that means the CNR target value, at minimum dose. All DR systems exhibited higher DQE and significantly better image quality compared to CR systems. Generally switching, where available, to a target/filter combination with an x-ray spectrum of higher mean energy permitted dose savings at equal image quality. However, several systems did not allow to modify the AEC in order to apply optimal radiographic technique in clinical use. The best ratio image quality/dose was achieved by a unit with a-Se detector and W anode only recently available on the market.

Paper Details

Date Published: 18 March 2010
PDF: 11 pages
Proc. SPIE 7622, Medical Imaging 2010: Physics of Medical Imaging, 76220J (18 March 2010); doi: 10.1117/12.844150
Show Author Affiliations
Nadia Oberhofer, Health Service South Tyrol (Italy)
Alessandro Fracchetti, Health Service South Tyrol (Italy)
Margareth Springeth, Health Service South Tyrol (Italy)
Ehrenfried Moroder, Health Service South Tyrol (Italy)

Published in SPIE Proceedings Vol. 7622:
Medical Imaging 2010: Physics of Medical Imaging
Ehsan Samei; Norbert J. Pelc, Editor(s)

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