Doğan Bor1, Selma Tükel, Turan Olgar, Elif Aydin. 1. Department of Engineering Physics, Faculty of Engineering, Ankara University, Ankara, Turkey. bor@eng.ankara.edu.tr
Abstract
PURPOSE: To assess variations of glandular doses for a group of patients when different dose modes are selected for a specific system. MATERIALS AND METHODS: All measurements were obtained with a Senographe DMR mammography unit (GE Medical Systems). Automatic exposure control with either contrast or standard mode was routinely used in patient examinations. Entrance surface air kerma (ESAK) values were estimated from the postexposure mAs and from the recorded data. Subsequently the mean glandular dose (MGD) for each view was calculated using the conversion factors assuming 50% glandular and 50% adipose tissue composition. RESULTS: The average MGD for the right craniocaudal view for all beam qualities was 1.65 mGy, and 46.7 mm was the average compressed breast thickness for this view. Average MGDs were 1.61, 1.76, and 1.35 mGy for Mo-Mo, Mo-Rh, and Rh-Rh anode filter selections, respectively. Conversely, 2.18 and 1.47 of breast doses were measured for contrast and standard dose modes at the most often used (Mo-Mo) anode filter selection. CONCLUSION: Breast dose measurement techniques with the standard phantom or on real patients are easy to implement for the mammography users. Obtaining ESAK versus breast thickness relationship is useful for retrospective dose evaluation; better correlation can be established (67% vs. 52%) if they are generated separately for each dose modes.
PURPOSE: To assess variations of glandular doses for a group of patients when different dose modes are selected for a specific system. MATERIALS AND METHODS: All measurements were obtained with a Senographe DMR mammography unit (GE Medical Systems). Automatic exposure control with either contrast or standard mode was routinely used in patient examinations. Entrance surface air kerma (ESAK) values were estimated from the postexposure mAs and from the recorded data. Subsequently the mean glandular dose (MGD) for each view was calculated using the conversion factors assuming 50% glandular and 50% adipose tissue composition. RESULTS: The average MGD for the right craniocaudal view for all beam qualities was 1.65 mGy, and 46.7 mm was the average compressed breast thickness for this view. Average MGDs were 1.61, 1.76, and 1.35 mGy for Mo-Mo, Mo-Rh, and Rh-Rh anode filter selections, respectively. Conversely, 2.18 and 1.47 of breast doses were measured for contrast and standard dose modes at the most often used (Mo-Mo) anode filter selection. CONCLUSION: Breast dose measurement techniques with the standard phantom or on real patients are easy to implement for the mammography users. Obtaining ESAK versus breast thickness relationship is useful for retrospective dose evaluation; better correlation can be established (67% vs. 52%) if they are generated separately for each dose modes.
Authors: Isabelle Thierry-Chef; Steven L Simon; Robert M Weinstock; Deukwoo Kwon; Martha S Linet Journal: Radiat Res Date: 2011-10-12 Impact factor: 2.841