Congress:
EuroSafe Imaging 2021
Keywords:
Breast, Radioprotection / Radiation dose, Mammography, Dosimetry, Radiation safety, Dosimetric comparison, Quality assurance
Authors:
W. Skrzyński, K. Pasicz, E. Fabiszewska
DOI:
10.26044/esi2021/ESI-13798
Methods or background
Dose comparison was performed for five mammography units used in our institute (Hologic Selenia, GE Pristina, three Siemens Mammomat Inspiration units). For each unit, data on exposure parameters, displayed AGD values, and compressed breast thickness were gathered for several groups of 50 patients (200 exposures), examined in various periods between years 2015 and 2020 (total 20 groups of patients). The data included exposure parameters (anode, filter, tube voltage, tube loading), displayed AGD values, compressed breast thickness, and image format (small or large).
In each period several measurements were made, providing data necessary for the independent calculation of AGD. Air kerma and half-value layer values were measured for all clinically used beam qualities with Piranha Black 657 meter (RTI Electronics AB, Sweden). Additionally, tests of thickness indicator accuracy were performed as described in the European guidelines [2], separately for small and large compression plates. Several slabs of PMMA were used for the test, with thickness ranging from 2 cm to 7 cm. Results of the test were then used to correct data on breast thickness.
Individual average glandular doses were calculated independently for patients, using Dance’s method [2-4] and an in-house Excel spreadsheet. Average glandular doses are calculated by multiplication of air kerma by conversion factors, which depend on beam quality and the thickness of the compressed breast. Actual exposure parameters, corrected breast thickness data, and results of tube output measurements were used to calculate incident air kerma. Information on beam quality (anode/filter/HVL) and corrected breast thickness were used to obtain conversion factors.
For each group of patients, displayed and calculated doses were compared between themselves, and compared with achievable and acceptable dose levels as outlined in the European Guidelines.