SU-E-T-164: Characterization of Breast Deformation During Accuboost TM Treatment




During treatment using AccuboostTM (Advanced Radiation Therapy, Tyngsboro, MA) applicators the breast is compressed between two paddles in order to immobilize it. This causes the breast tissue to expand. The purpose of this study was to analyze the nature of this deformation.


CT scans of a breast phantom (Computerized Imaging Reference Systems, Norfolk, VA) were acquired at different compressions in the cranial-caudal (CC) direction. These were performed by placing the phantom between two plates whose position is controlled by a manual crank. The phantom masses were contoured in order to simulate the clips placed after surgery. For all scans the mean distance between the masses was computed. Additionally, deformable registration was performed between two scans using the Velocity software (Varian Medical Systems, Palo Alto, CA) to assess the shifts of each of these masses.


As the compression increases so does the average distance between the masses. The relationship between deformation and compression is not linear. Additionally, the largest displacements are in the direction of compression. The mean shift is 1.8mm. The shifts in the RT-LT direction and ANT-POST direction are 1.1 mm and 0.7 mm respectively


When treating patients the clips shift their position as a Result of the plate compression. For CC compressions this is not a problem if they shift their position primarily in the superior-inferior direction. The problem of not being able to cover all clips (target area) can arise when they shift position on a plane perpendicular to the patient. For clips which are already near the chest wall, care should be exercised not to compress the breast in such a way as to move those clips out of the treatable area.These preliminary results show a larger shift in the RT-LT direction than the ANT-POST one. Further research will seek to either confirm or infirm this.