Chulalongkorn Medical Journal


Background : Breast tomosynthesis is a new technology to improve the sensitivityand specificity of mammography by eliminating tissue overlap. Breasttomosynthesis is essentially a modification of a digital mammography (2D)to enable the acquisition of a three-dimensional (3D) volume of thin sectiondata. Images are reconstructed in conventional orientations by usingreconstruction algorithms similar to those used in computed tomography(CT).Objective : To determine the average glandular dose (AGD) and the entrancesurface air kerma (ESAK) from cranio-caudal (CC) and medio-lateraloblique (MLO) projections in 2 dimension and 3 dimension imaging modes.Design : Retrospective descriptive dataSetting : Breast Imaging Unit, Department of Radiology, King ChulalongkornMemorial HospitalMethods : Patients’ data from digital breast tomosynthesis (DBT) system wereanalyzed in terms of the compressed breast thickness (CBT, mm), peakkilovoltage (kVp), tube current time (mAs), average glandular dose (AGD,mGy) and the entrance surface air kerma (ESAK, mGy) in 2D and 3Dimage sets from one compression.Results : One hundred and ninety eight female breast cancer patients with breastconservingsurgery were studied using digital breast tomosynthesis systemfrom January-December 2012. The CBT, kVp and mAs were recordedwhen the tungsten target with rhodium or silver filters were chosen in 2Dand the tungsten target with aluminum filter were chosen in 3D images.The mean compressed breast thickness (CBT) was 54.5 mm for craniocaudal,CC and 55.0 mm for medio-lateral oblique, MLO views. The meanAGD and ESAK for 4 views of both sides in 2D and 3D were 1.7, 6.5 and2.0, 7.0 mGy respectively. The mean AGD and ESAK in 3D imaging modewere 16.1 % and 6.1 % higher than the mean AGD and ESAK in 2D imagingmode. No significant relationship was found between AGD and CBT in 2Dimaging mode of a correlation coefficient of 0.36 and a good correlationcoefficient of 0.87 in 3D imaging mode.Conclusion : The mean CBT was 54.7 mm, the mean AGD from digital breasttomosynthesis (DBT) system was 2.0 mGy, the mean AGD of full fielddigital mammography (FFDM) CC views 1.65 mGy and MLO was 1.75results in overall mean AGD of 1.7 mGy. Both values of 2D and 3D are stilllower than 3.0 mGy limit for single view of dose reference level (DRL) setby MQSA.


Faculty of Medicine, Chulalongkorn University

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