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ST: Strahlen- und Medizinphysik

ST 11: Verbesserung der Bestrahlungsplanung

ST 11.4: Talk

Tuesday, March 14, 2006, 17:20–17:30, D

Time resolved patient imaging in treatment position — •Siri Jetter, Lars Dietrich, Thomas Tücking, Simeon Nill, Bernd Hesse, and Uwe Oelfke — Department of Medical Physics, DKFZ Heidelberg, Germany

To investigate the correlation between diagnostic time resolved computer tomography (4D CT) data and 4D cone beam CT (CBCT) data for breathing motion we developed a method for the acquisition and reconstruction of 4D CBCT data. Our cone beam imaging system, integrated into a treatment machine allows for the acquisition of images of the patient in treatment position. The breathing phase is monitored with a respiratory gating system (RGS) based on a pressure sensor in a fixation belt positioned on the patient’s abdomen. To evaluate the correlation between breathing signal and inner organ motion the position of the diaphragm is compared to the output of the RGS. For different breathing phases cone beam CT images are reconstructed and compared to the images obtained with a diagnostic 4D-CT scanner. We show that external signal and the movement of the diaphragm correlate closely in amplitude and phase. Comparison of 4D CBCT images with corresponding diagnostic 4D CT data allows for a repositioning of the patient in spite of respiratory movement. Furthermore inner organ and tumor movements can be evaluated. These data are essential for the design of time adapted treatment strategies.