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TP7 4D Behandlungsplanoptimierung und Bewegungsdetektion mittels Radiografie

In Ion beam radiotherapy, narrow scanning beams are used to deliver highly localized dose distributions to the patient. In treatments of organs moving during the beam delivery interplay effects between the two motions occur, resulting in undesired dose distributions. To minimize those effects, several motion mitigation techniques were proposed. This project concentrates on gating (beam delivered only in a particular motion phase) and tracking (target motion followed by the beam).

To enable their clinical implementation, dedicated 4D treatment planning as well as a high precision detection of the actual target position is necessary. We plan to implement 4D optimization of treatment plans for scanned ion beam therapy. These offer the advantage that the additional degrees of freedom given by the moving target are exploited in the optimization process. We will focus on 4D optimization for beam tracking with the aim to achieve tracking without energy variation and beam gating.

For determination of the internal target position, we will investigate ion radiography. Radiography provides the potential of high contrast images gained at low dose. The pixelized semiconductor detector “Timepix” will be used to register single ions behind the patient. Based on the measurement of their energy deposition in the detector, direction and fluence, imaging techniques will be developed. The technique with the best performance to visualize moving targets at a minimal dose to the patient will be identified.

If successful, the techniques of dedicated 4D treatment plan optimization and target position detection will allow improved radio-therapeutic treatments of tumors in moving organs like lung, liver and pancreas by scanning ion beams. The techniques will be clinically implemented at the HIT facility in Heidelberg in the near future, what enables to exploit this high-end radiotherapy for radioresistant tumors in those new locations.

Ausgewählte Literatur

Gwosch K, Hartmann B, Jakubek J, Granja C, Soukup P, Jäkel O, Martišíková M. Non-invasive monitoring of therapeutic carbon ion beams in a homogeneous phantom by tracking of secondary ions. Phys Med Biol. 2013 Jun 7;58(11):3755-73

Richter D, Schwarzkopf A, Trautmann J, Krämer M, Durante M, Jäkel O, Bert C. Upgrade and benchmarking of a 4D treatment planning system for scanned ion beam therapy. Med Phys. 2013 May;40(5):051722

Steidl P, Richter D, Schuy C, Schubert E, Haberer T, Durante M, Bert C. A breathing thorax phantom with independently programmable 6D tumour motion for dosimetric measurements in radiation therapy. Phys Med Biol. 2012 Apr 21;57(8):2235-50

J. Jakubek, C. Granja, B. Hartmann, O. Jäkel, M. Martisikova, L. Opalka, S. Pospisil: Imaging with Secondary Radiation in Hadron Therapy Beams with the 3D Sensitive Voxel Detector, IEEE NSS/MIC/RTSD Valencia, Conf. Record (2011) 2281-2284

X. Llopart et al.: Timepix, a 65k programmable pixel readout chip for arrival time, energy and/or photon counting measurements , Nucl. Instrum. Meth. A 581 (2007) 485

M. Martisikova, J. Jakubek, C. Granja, B. Hartmann, L. Opalka, S. Pospisil and O. Jäkel: Measurement of secondary radiation during ion beam therapy with the pixel detector Timepix, Journal of Instrumentation 6 C11014 (2011)