ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

the difference in percentage between the compression force obtained in the simulation
of breast compression considering gravity and without considering it.
Table 5. Difference between the compression force obtained in the simulation of breast
compression considering gravity and without considering it (%).
Patient
Differences for the
linear elastic model
Differences error for
the Neo-Hookean
model
Differences for
Mooney-Rivlin
model
Differences for the
Polynomial model
P1 8.72% 7.07% 0.44% 6.74%
P2 9.48% 31.46% 0.15% 11.12%
P3 8.39% 2.58% 0.44% 1.45%
P4 27.09% 5.88% 6.16% 8.22%
P5 36.21% 10.91% 5.25% 14.81%
P6 21.26% 6.51% 0.02% 7.26%
5. DISCUSSION
The real compression force obtained ranged from 78 to 138 N. This agrees with
Sullivan et al. in [15] where the values ranged from 49 to 186.2 N. In our case, none of
the four models used in this work matched the real compression force for all patients.
The linear elastic and Neo-Hookean models provided values under of this range.
Mooney-Rivlin model was close to these values for two cases (P1, P4) where the real
forces were (118 N, 108 N), respectively. However, for the other four patients, greater
values were obtained for the compression forces which were far to be in the range. The
values obtained for the polynomial model where within the range of the real forces in
three cases (P1, P4, and P5), although, it was not possible to achieve the real forces
which were (118N, 108N, 137N). However, the values obtained for the rest of patients
were no so far of the real force range as in the case of considering the Mooney-Rivlin
model. These results suggest that a Polynomial model could represent the behavior of
the breast compression accurately, although the parameter should be measured for each
patient specifically. On the other hand, prone gravity-loaded breast should not be used
as an approximation of unloaded reference state for X-ray mammography simulation,
since important errors can be committed (Table 5). Although low differences between
the compression forces were obtained for the Mooney-Rivlin model, these models do
not provide compression forces closer to the real ones.
6. CONCLUSIONS
This work has proved that prone gravity-loaded breast should not be used as an
approximation of non-deformed state for X-ray mammography simulation since errors
of about 10% could be committed. However, the approximation to the zero-strain state
of the breast presented in this work, which take into account the gravity, can be used for
more accurate simulations of the breast compression during an X-ray mammography.
7. ACKNOWLEGMENTS
This work has been partially funded by the Spanish Ministry of and Science and