Implementation of the European protocol for quality control of the technical aspects of mammography screening in Bulgaria
1 National Centre of Radiobiology and Radiation Protection, 132 Kliment Uhridsky blv., Sofia 1756, Bulgaria
2 Radiological Department, Regional Oncological Hospital, Stara Zagora, Bulgaria
3 Department of Medial Imaging, St Georgi University Hospital, Plovdiv, Bulgaria
* Corresponding author: j.vassileva{at}ncrrp.org
The results from the national pilot project on implementation of the European protocol for the quality control (QC) of the technical aspects of mammography screening as well as the European protocol for dosimetry in mammography in Bulgaria are presented. A QC programme for mammography equipment and a standardised measurement protocol were created. The full QC programme was tested on four mammography units of different types and ages. A national survey was performed for entrance surface air kerma (ESAK) on 20 units using a 45 mm PMMA standard phantom. Average glandular dose (AGD) was calculated using the conversion coefficients from the European dosimetry protocol. The survey demonstrated considerable differences in the technical condition of the mammography units that resulted in varying image quality. The measured values of ESAK showed significant variations. Doses for 
45% of the units were found to be below the European reference level. The values for AGD ranged from 0.35 to 3.47 mGy. The main problems found were film processing, optical density (OD) control settings and AEC adjustment. The results showed the importance of film OD measurements parallel to dose measurements. The X-ray mammography in the country needs optimisation. Comprehensive quality assurance programme should be adopted in all departments covering permanent QC of the equipment, image quality and breast dose.