Robotic ultrasound guidance for real-time motion compensated radiation therapy (RobUST), Phase II

The project will analyse the possibility of cooperative use of two robotic systems in radiation therapy. An advantage of the clinically used CyerKnife system is the large number of degrees of freedom when selecting the directions of the beams used for treatment and its capability of compensating for respiratory motion by synchronously moving the radiation source. This allows for creating very precise and homogeneous dose distributions with steep gradients. Until now, the clinical state of the art is motion tracking with externally measured surrogate signals and infrequent X-ray or CBCT imaging. The goal of the second phase of the project is the further evaluation of real-time target tracking using 3D ultrasound, ultimately allowing treatment without the need for surrogate signals. Additionally, this approach will also be able to deal with non-respiratory motion (like bowel motion, changes in bladder filling, etc.). In the first project phase, the basics of safe ultrasonic probe placement using robots were investigated and it was shown that the integration of the ultrasound robot into the treatment process is possible with regard to plan quality and irradiation time. Essential goal of the project "RobUST II is now to investigate, on the basis of the preliminary work of the first application phase, to what extent robot-assisted ultrasound can continuously image the target area in high-quality over the duration of a treatment fraction, whether and how movements and deformations of the structures can be detected sufficiently quickly and how the treatment parameters can be adapted to detected changes in real time.Motivated by this, the project comprises three research areas: fast ultrasound image processing, safe robot control and real-time adaptive treatment planning. While each of these research areas requires very specific expertise and skills, the final goal of the project is their integration into an optimized workflow and experimental evaluation of the entire system with respect to the goal of motion-compensated radiotherapy adapted to intra-fractional geometry changes.