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ST: Fachverband Strahlen- und Medizinphysik

ST 8: Strahlentherapie

ST 8.4: Vortrag

Dienstag, 27. März 2007, 14:45–15:00, Ch 12.0.16

Gated irradiation of moving targets with scanned particle beams — •Christoph Bert¹, Eike Rietzel¹, Alexander Schmidt¹, Stephan Brons², Nami Saito¹, Thomas Haberer², and Gerhard Kraft¹ — ¹GSI-Biophysics, Darmstadt, Germany — ²HIT Heidelberg, Germany

The treatment of moving targets with scanned particle beams results in interplay effects between motion and scanning progress. Interplay can lead to severe mis-dosage. GSI plans to treat moving targets with motion compensation by active beam adaptation [1].

Another possibility to treat targets in the presence of respiratory motion is gating [2]. For gating, particle extraction and organ motion are synchronized such that irradiation is typically applied during end-exhale breathing phases only. Simulations showed that gating can produce appropriate dose distributions but that it prolongs the irradiation time.

With a synchrotron, knock-out extraction is required to gate irradiations [3]. Within one beam pulse, knock-out extraction allows to pause and resume irradiations based on a signal from the motion detection unit. Knock-out extraction and gating were implemented at GSI for research and further developments. Experimental studies with moving radio-sensitive films showed that gating can effectively mitigate target motion.

[1] Grözinger et al, Phys.Med.Biol., 51(14), 2006

[2] Minohara et al., Int.J.Radiat.Oncol.Biol.Phys., 47(4), 2000

[3] Noda et al, Nucl.Instr.Meth. A374, 1996