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    Estudo longitudinal da qualidade da imagem mamográfica em sistemas digitais associado ao processo de otimização da dose glandular média
    (Universidade Federal de São Paulo (UNIFESP), 2014-06-11) Alves, Fatima Faloppa Rodrigues [UNIFESP]; Medeiros, Regina Bitelli Medeiros [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    Objective: Contribute to the development of practices that may assist AGD?s optimization process associated to image quality in digital systems (CR and DR). Method: Two pieces of mammographic equipment (Lorad and Performa) were tested regarding performance with CR Kodak system and with Digital mammographic equipment (DR) GE, and image viewing systems have been assessed in the period between January/ 2012 to January/2014. IPS uniformity was checked in outpatient routine until July/2013 and, after their replacement, in October/2013. AGDs were calculated using PMMA semicircular plates with 1 and 2 mm thickness, and physical properties of images were assessed through quality parameters: FTM, SNR, CNR and FOM. Regarding breast tissue, AGDs were estimated in MLOE projection according to mammographic density through a databank with information from 1071 patients including: age, biometry and operational technical data of the exams. An electronic spreadsheet made it possible to obtain mAs values so as to keep AGDs below European protocol limits, and, at the same time, to maximize CNR values. Simulated image quality and structure detection were performed with CIRS-11A phantom. Mammographic image quality was analyzed based on the quality criteria recommended by IAEA. Results: IPs uniformity ranged between 9,9% and 92,3% from January/ 2012 to July/2013, and after these IPs were changed, uniformity ranged less than 7%. AGD values were above Euref?s limits for both PMMA and breast tissue, for most of the period between March/2012 and July/2013, in Lorad and Performa equipment. In the Digital System, AGDs remained within Euref?s PMMA and breast tissue limits. However, regarding mammographic density, AGDs were inferior in the Digital System. FTM, SNR and CNR parameters remained above Euref?s reference limits in the same period in which nonconformity of IPs? uniformity was observed. After IPs were replaced, mAs was on average reduced in 30% and 10%, with average CNR gain of 13% and 7% in Lorad and Performa equipment. Detection simulator?s structure ranged between 0,165 and 0,275mm for microcalcification and between 1,19 and 2,38mm for tumor mass, but there was no variation in detection of fibers. In clinical image analysis, although 99% of the images were considered acceptable for diagnosis, in 62% of the cases it was not possible to view the pectoral muscle in left CC positioning, and in 44% the angle of inframammary fold in left MLO projection, which can be attributed to positioning error. Specific viewbox luminance values were out of the limits set by the norm 543/98. Monitors had luminance superior to 500cd/m2. Conclusion: It is suggested, as a practical method, monthly CNR and SNR analysis, and the use of an electronic spreadsheet is suggested, so as to reduce time and make AGDs optimization process easier. The deterioration of IPs caused increase in AGDs, loss in image quality and variation in uniformity, in SNR, in FTM and in FOM which points to the necessity of establishing an IP uniformity base line and other quality parameters. Monitoring quality of clinical images allowed the detection of failures in positioning, highlighting the need for training. AGDs that were calculated in Digital System were inferior to the CR system, showing differences between technological characteristics. The use of different target/filter combinations, as well as a superior output in Digital System, may have contributed to achieving lower doses. It stresses the necessity to establish specific quality tests and to establish a revision of norms for Digital Systems in Brazil.