05-03-2013, 10:20 AM
Nonlinear Elasto-Mammography for Characterization of Breast Tissue Properties
Nonlinear Elasto-Mammography.pdf (Size: 1.15 MB / Downloads: 36)
Abstract:
Quantification of the mechanical
behavior of normal and cancerous tissues has
important implication in the diagnosis of breast
tumor. The present work extends the authors’
nonlinear elastography framework to incorporate the
conventional X-ray mammography, where the
projection of displacement information is acquired
instead of full three-dimensional (3D) vector. The
elastic parameters of normal and cancerous breast
tissues are identified by minimizing the difference
between the measurement and the corresponding
computational prediction. The material parameters
are identified with consideration of measurement
error.The results demonstrate that the projective
displacements acquired in X-ray mammography
provide sufficient constitutive information of the
tumor and prove the usability and robustness of the
proposed method and algorithm.
INTRODUCTION
Breast cancer is a major threat to public health in
the world. In USA and Europe, approximately 10%
of women develop breast cancer during the course
of their lives. While the specific causes of breast
cancer are unknown, early detection and
characterization of breast tumors is the key to
successful treatment. Currently, X-ray
mammography, a low dose X-ray imaging
modality, is the primary diagnosis method in
clinics. While being more efficient in detecting
malignancies as age increases or the breast
becomes fatty, mammography fails to identify
small cancers in dense breasts. About 80% of
suspicious masses referred by mammography for
surgical breast biopsy are in fact not malignant.
These false positive mammograms may induce
patients’ anxiety, distress, and intrusive thoughts.
Linear elasto-mammography
This framework was developed to generate the
elastograms of breast tissues, by combining the
conventional low-dose X-ray mammography with
linear elastography framework. Instead of applying
ultrasound or magnetic resonance as in the previous
elastography research, elasto-mammography uses
displacement information extracted from
mammography projections before and after breast
compression.Case studies with numerical breast
phantoms showed that the displacement
measurement obtained from mammography is
sufficient to identify the material parameters of
breast tissues and tumors within the framework of
linear elasticity.
RESULTS AND DISCUSSION
Ideal Input:
Table 1 shows the initial estimate and
reconstructed results, together with the real values
for comparison. The results in the first part are
based on the ideal input. It is d.emonstrated that the
reconstructed resultsare very close to the real
values. The maximum error is 0.3 %( γ for tumor)
since the effect of the tumor on surface force
measurement is the smallest. Reconstructions using
differentinitial estimates have been conducted and
very similar results are found, which indicates the
efficiency and uniqueness of the proposed
nonlinear elasto-mammography using projective
measurements. After about 50 iteration steps, their
relative errors are well within the range of 5%.
Then, they experience some minor adjustment. In
contrast, elastic parameters of the tumor converge
slower. The reduction of necessary loadings is
possible because mammography projection
provides displacement on the surface of the tumor,
which contains direct information of the mechanics
of the tumor. Our previous nonlinear elastography
study [13] takes only measurement on the breast
surface as input.