This poster is published under an
open license. Please read the
disclaimer for further details.
Keywords:
Breast, Mammography, Dosimetry, Dosimetric comparison
Authors:
C. Tromans, A. Chan, R. Highnam; Wellington/NZ
DOI:
10.1594/ecr2014/C-0360
Results
Manufacturer & Patient-Specific Dose Comparison
Patient-specific MGD estimates per view (Figure 2) were highly correlated with the GE- and Hologic-reported doses (PCC’s = 0.916 and 0.879,
respectively).
However,
the overall average MGD per view for reported and patient-specific estimates were significantly different: 2.04 and 2.27 for GE,
respectively,
and 1.90 and 2.21 for Hologic,
respectively (Figure 3).
Compared to patient-specific estimates,
GE and Hologic tended to underestimate MGD,
more so in dense and fattier breasts respectively (Figure 4).
Dose Comparison Over Time
Both the reported and patient-specific MGD estimates over time were poorly correlated (Figure 5).
PCCs for women imaged on GE first were 0.466 and 0.367 for the reported dose and patient-specific dose estimates,
respectively.
PCCs for women imaged on Hologic first were 0.144 and 0.147 for the reported dose and patient-specific dose estimates,
respectively.
These results indicate that the MGD received by women can vary widely over time.
As indicated earlier,
this could be due to patient,
technologist or manufacturer-based reasons and in further work we will seek to better identify the reasons utilizing the patient-specific results where we understand the dose algorithm being used and the glandularity value used.
For the 6 women with multiple mammograms available,
the trends over time for average MGD were similar between the reported and the patient-specific estimates (Figures 6-11).
For some women,
the average MGD received,
per view,
was fairly consistent over time (Figures 7 and 10).
In contrast,
Figure 9 shows a patient experiencing the largest change in average MGD (patient-specific estimate) over two consecutive years (i.e.
3 mGy),
which corresponded with a -5.8 mm and +1.9% change in compressed breast thickness and VBD,
respectively. Patient,
technologist and manufacturer-related factors contributed to some women experiencing larger variations in average MGD,
whilst others experienced more consistent doses,
over several years.