2012 Proceedings - International Tissue Elasticity Conference

019 FULLY AUTOMATED BREAST ULTRASOUND ELASTOGRAPHY SYSTEM.
Reza Zahiri Azar 1,2 , Corina Leung 1 , Thomas Chen 1 , Kris Dickie 1 , John Dixon 1 , Kwun–Keat Chan 1 ,
Laurent Pelissier 1 .
1 Ultrasonix Medical Corporation, Richmond, BC, CANADA. 2 University of British Columbia,
Vancouver, BC, CANADA.
Background: The automated breast ultrasound system (ABUS) has recently been introduced as a new
imaging device for breast screening and monitoring of cancer treatment (Ultrasonix Medical Corp,
Richmond, BC, Canada). ABUS enables clinicians to acquire full volumes of the breast tissue in less than
a minute. During the exam, the patient lies face down on the ABUS bed while the breast rests inside the
imaging dome without undergoing any compression. Once the patient is comfortable, the ABUS
automatically rotates a custom concave ultrasound transducer (-12cm radius and 11cm foot print) 360º
around the breast tissue to capture full 3D ultrasound volumes. The volume data are then transferred to
the viewer for reviewing purposes.
Aim: To add strain imaging capability to the ABUS system for automated 3D strain imaging of the breast.
Methods: The ABUS system is equipped with a motion stage to allow for adjusting the position of the
dome with respect to the bed. This position adjustment is used mainly to ensure full tissue contact with
the ultrasound transducer as well as making the scanning comfortable for the patient. In this work, this
motion stage was used to apply slight compression to the breast tissue. Thus, allowing us to
automatically acquire pre– and post–compression radiofrequency (RF) volumes for elastography. To
validate the system, an experiment was performed on a breast elastography phantom (Model 059, CIRS,
Norfolk, Virginia, USA). The phantom was placed upside down inside the dome and fixed to the bed. First,
pre–compression RF volume and the corresponding B–mode volume (400 frames per 360º) were acquired
(7cm imaging depth, 384 scan lines, 10MHz transmit frequency and 40MHz sampling frequency). Using
the motion stage, the phantom was then compressed approximately one percent. The post–compression
RF volume was then acquired using the same settings. Axial displacements and strain images were
estimated from these two RF volumes using the cross–correlation algorithm (2mm window size with 75%
window overlap) and the least squares strain estimator (3mm kernel size). Finally, both strain volume and
B–mode volume were transferred to the viewer for review.
Results: An example of the corresponding coronal, sagittal and transverse views of both B–mode and
strain images are shown in Figure 1. This Figure shows that the inclusions which can not be seen in the
B–mode views can easily be detected in the strain views.
Conclusions: Compared to the free hand elastography, the proposed automated system is expected to be
less prone to strain imaging variations which are introduced by different scanning and compression
techniques. Also, the fact that the entire breast tissue is resting in the dome minimizes the unwanted
tissue motions and enables the system to reproduce the strain images. Currently the usability of the
system in clinical setup is being studied. Further investigations are required to study the effect of the
internal tissue motions, due to breathing and heartbeat, in the estimated strain images.
(a) B–mode (b) Strain
Figure 1: An example of corresponding coronal (left), sagittal (top right), and transverse (bottom right) cross sections
of B–mode volume (a) and strain volume (b). In the strain views, dark represents low strain value and bright
represents high strain value. Also, regions with low correlation coefficients are shown in white.
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