4D Treatment (Planning) Workshop
at GSI Darmstadt
Theorieseminarraum -
Information

Title:	Ms.
Family Name:	Laube
First Name:	Kristin
Gender:	female
E-Mail:	k.laubefzd.de
Profession:	Physicist
Affiliation for Badge:	TU Dresden
Institute:	OncoRay - National Center for Radiation Research in Oncology
Address (Street):	Fetscherstraße 74, PF 41
Postal Code, City:	01307 Dresden
Country:	Germany
Phone:	0351 260-2973
Fax:	0351 260-3700
Arrival Date:	December 8
Departure Date:	December 10
Hotel Information:	GSI Guesthouse and Hostel
Tour:	No
Author(s):	K. Laube(1), F. Fiedler(2), W. Enghardt(1)
Institute(s):	(1) OncoRay - National Center for Radiation Research in Oncology, TU Dresden (D) (2) Institute of Radiation Physics, Forschungszentrum Dresden-Rossendorf (D)
Title:	Image reconstruction for the quality control of moving target irradiation with 4D in-beam PET
Abstract ( 300 words ):	In hadron therapy only slight density deviations in the tissue along the ion path can cause serious over- and underdosage. Therefore, a method for assessing the relevant parameters of the applied dose distribution is required. Positron emission tomography (PET) is the only quality control system that has been implemented clinically yet but only for static targets. The planned implementation of ion beam therapy for intra-fractional moving tumor sites demands an upgrade of the dose verification system. 4D in-beam PET phantom measurements have been performed at the experimental treatment site at GSI. Challenges in the reconstruction process occur from the long half-lives of the radioactive isotopes (20 min for ¹¹C). Due to the motion relative to the fixed scanner coordinates, normally the positron emitters decay at different positions as they were created and the resulting annihilation photons are detected in the correspondingly shifted LORs. A phase wise reconstruction of the registered listmode data seems to be inadequate, because of the low statistics in the single motion phases. A 4D-MLEM reconstruction algorithm will be presented that relies on correct motion detection throughout the whole measurement and the known deformation matrices between the single motion phases. The algorithm combines in each iteration step the advantage of motion handling by phase separation and the high statistics of all registered events. Furthermore, the spatial limit of detectable motion influence by means of sinusoidally moving point sources of different motion amplitudes will be discussed.

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