mediri developed a tracking system based on ultrasound-imaging to improve the accuracy of radiation therapy in the abdomen. Based on diagnostic ultrasound imaging data, a three-dimensional real-time tracking of the radio therapy target volume or organs like liver and kidney is established.

Two small, specifically developed ultrasound probes – scanning four slices of the abdomen or the retro-peritoneum – are positioned on the skin of the patient during RT-procedure. The real-time signals of the US-probes are analyzed online to follow predefined pronounced structures such as organ borders, vessels or the tumor as such. Based on this tracking information, the linear accelerator can be triggered or - in a second step – the irradiating beam could be steered in alignment with the targets moving position.

Besides translation, our tracking algorithm could analyze the rotation as well as the deformation of the targeted structures.

The developed tracking software is robust and provides highest safety standards. Unforeseen events which lead to loss of the tracked structure, e.g. due to an extraordinary deep breath, are detected automatically and the irradiation is stopped immediately. Once the targeted structures have returned to the visual plot of the ultrasound probes, the software recognizes the structure automatically and the therapy can continue.

The clinical evaluation of our tracking system in conformal photon therapy will be performed together with the Department of Radiation Oncology of the University Medical Center Mannheim/University of Heidelberg.