Ultrasound Based Localization of Lumpectomy Bed in Anatomical Coordinate System

1. Abstract The feasibility, toxicity and efficacy of Partial Brest Irradiation (PBI) are
currently being studied by major cooperative groups such as the NSABP, and RTOG as well as
by several major academic institutions. PBI entails definitive radiation to the lumpectomy
site while minimizing radiation to the remaining breast tissue. The success of PBI is
dependent in no small part to proper target localization. In radiation therapy, to treat an
internal structure, external landmarks must be used to calculate the position of the
internal target. These external landmarks can easily change in a non-rigid structure (e.g.
breast), which would nullify their use as a reference. To address this problem, there have
been recent advances in the application of ultrasound (US) technology in target localization
especially with respect to the prostate. Transcutaneous tracked US emerged as the most
suitable non-invasive daily prostate localization tool. In this procedure an US probe is
tracked and spatially registered with respect to the treatment machine, linear accelerator.
Thus if one localizes the target anatomy in the US images, then the position of the target
is automatically known with respect to the linear accelerator, so that the accelerator can
be correctly aimed.

Unfortunately, contemporary US imaging is not sufficiently sensitive to delineate the
lumpectomy bed for PBI. We propose to supplant B-mode imaging with a novel US elasticity
imaging (USEI) method to delineate the subtle and complex boundaries of the lumpectomy
cavity. Our preliminary studies suggest that USEI may be superior to B-mode imaging (see
statistical section and Ref. 6-7). However our work was only done in ex-vivo tissue models.
In the literature, there are many studies showing the superior sensitivity and specificity
of strain imaging compared to regular B-mode imaging7.

The benefit of developing a way to use ultrasound for target localization is clear.
Identification of the target would no longer be dependent on unreliable external landmarks
but now on direct internal information. As a consequence, targeting errors, most commonly
associated with patient positioning, could be significantly reduced or practically
eliminated. Thus, we propose to study the ability of USEI to detect and characterize the
lumpectomy bed in-vivo using CT data as ground truth. We will pursue our work in two
specific aims:

Aim 1: Describe the concordance between the lumpectomy bed's center-of-mass (COM) as
determined by USEI and CT.

Aim 2: Describe the concordance between the lumpectomy bed volume as measured by USEI and
CT.

Inclusion Criteria:

- Women with breast cancer, who are status post lumpectomy and are scheduled to have
radiation therapy, will be eligible.