IPEM MPEC 2015
MGD (Mean Glandular Dose) in one of the dosimetric quantities used in mammography. The test protocol to obtain MGD to typical breast is outlined in the NHSBSP Equipment Report 0604. This method consists in using blocks of PMMA as breast substitutes. The formula to obtain the MGD depends on the factors g, c, and s calculated by Dance. While s factor takes into account the use of different target/filter combinations; g and c factors introduce the correction due to the breast glandularity therefore depend on the beam quality and are tabulated as a function of HVL (half value layer).
The study is based on data collected in 2014 from five DR mammography models and patient breast doses. The difference from calculated MGD values (%) was obtained for each model.
Plots comparing MGDC and MGDD values against PMMA and real breast thicknesses showed the different behaviour and accuracy depending on models. Further analysis of the difference from MGDC values (%) demonstrated that even though doses calculated were within tolerance of +30/-30% for system displayed doses, the accuracy between calculated and displayed varied from model to model. It is noticed that the three manufacturer’s trendline is clearly different in each case.
This suggests further work needs to be done to improve and standardised system displayed doses and calculated MGD.
Conference Proceedings & Abstracts