AbstractID: 9280 Title: Measurement of Setup Variation in Radiotherapy of Breast
Cancer Using a 3D video-Imaging System
A major challenge during the course of radiotherapy of breast cancer is to deal with
breast variations caused by tissue inflammation, cysts or post-operative seroma
formation, ipsilateral arm repositioning, and thorax respiration motion. We have
introduced a 3D-video system to measure the breast shape and location changes in the
daily treatment. Once the patient is set up in the treatment position, we would quickly
capture the 3D surface of breast. The surface image should be transformed into the
machine coordinate system through a template-based calibration. By digitizing skin
markings on the surface images, we could easily determine the midsternal slope, medial
and lateral entrance points, and the outlines of the regions of interest such as entire breast,
surgical bed, and axillary lymph node. The surface shape and treatment-volume within
the regions of interest would be compared with the same regions on the reference-surface
image obtained at the simulation time. Any pathlength changes in the external x-ray
beams would be readily used for calculating the variations in the dose and the dose
distribution so that any significant setup error and dose deviation of the treatment could
be identified and avoided. Our primary results in a clinical trial indicate that the system
can measure small (2-mm) localization and shape changes and has a high precision in
repeated measurements by using specific skin markers to mapping the surface images and
predefined area of interest in different images. This system is applicable to patients who
may have black, brown, or white skins.