Average glandular dose (AGD) is used to describe radiation dose in mammography. Diagnostic reference levels (DRLs), and acceptable/achievable dose levels in breast cancer screening are expressed as AGD [1,2]. The average glandular dose is automatically calculated for each exposure and displayed to the operator, and it is stored within a header of a DICOM file. The aim of the work was to check the reliability of AGD values displayed by mammography units by comparing them with calculated values.

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...

Obtained differences between displayed and calculated results varied between units and periods. The maximum average difference between displayed and calculated doses in a group of 50 patients was equal to 0.4 mGy (22% of the average calculated dose). Even smaller differences could strongly affect results of dose evaluation. For GE unit in November 2018, displayed AGD values did not exceed achievable levels in 91% of cases, while for calculated doses it was true only for 65% of cases (average dose difference was 0.17 mGy) (Figure...

Observed differences between displayed and calculated doses can affect results of comparison of doses with acceptable and achievable dose levels, DRLs, or comparisons between different units. When comparing displayed values with reference values or dose limits, the uncertainty of displayed doses and the compressed breast thickness should be taken into account.

[1] International Commission on Radiological Protection. Diagnostic reference levels in medical imaging. ICRP Publication 135. Ann ICRP 2017;46. [2] European Commission. European guidelines for quality assurance in breast cancer screening and diagnosis. Fourth edition. 2013. [3] Dance DR. Monte Carlo calculation of conversion factors for the estimation of mean glandular breast dose. Phys Med Biol 1990;35:1211–9. https://doi.org/10.1088/0031-9155/35/9/002. [4] Dance DR, Skinner CL, Young KC, Beckett JR, Kotre CJ. Additional factors for the estimation of mean glandular breast dose using the UK mammography dosimetry protocol. Phys...

W. Skrzyński: Nothing to disclose K. Pasicz: Nothing to disclose E. Fabiszewska: Nothing to disclose