Bochum 1998 – wissenschaftliches Programm

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HK: Hadronen und Kerne

HK 69: Plenar

HK 69.1: Gruppenbericht

Freitag, 20. März 1998, 09:00–09:30, P

Positron Emission Tomography for Quality Assurance of Cancer Therapy with Light-Ion Beams — •W. Enghardt¹, J. Debus², T. Haberer³, B.G. Hasch¹, R. Hinz¹, O. Jäkel⁴, M. Krämer³, K. Lauckner¹, and J. Pawelke¹ — ¹Forschungszentrum Rossendorf e.V., Postfach 51 01 19, D-01314 Dresden — ²Universitätsklinikum Heidelberg, Strahlentherapie, Im Neuenheimer Feld 400, D-69120 Heidelberg — ³Gesellschaft für Schwerionenforschung, Planckstr. 1, D-64291 Darmstadt — ⁴Deutsches Krebsforschungszentrum, Im Neuenheimer Feld 280, D-69120 Heidelberg

The biological effects of swift light ions (preferentially ¹²C) and their unique capability of delivering a tumour-shape conformed dose distribution offer the possibility of an improved treatment of deep-seated, compact tumours in close vicinity of organs at risk. In such a delicate therapeutic situation an in-situ control of the irradiation is unavoidable. A method like portal imaging in photon therapy, where an image of the radiation penetrating the patient completely is used for position control, is obviously not feasible in the case of heavy ion therapy. However, positron emission tomography (PET) provides a solution of this problem by means of imaging the spatial distribution of β⁺-emitters that are produced as a byproduct of the irradiation via fragmentation reactions between the projectiles and the atomic nuclei of the tissue within the target volume.

On the basis of extended experimental and Monte Carlo studies on the generation of positron emitters via nuclear fragmentation reactions caused by light ions (6 ≤ Z ≤ 10) of 80 to 500 AMeV physical and technical solutions for in-beam PET-techniques of therapy monitoring, performed simultaneously with the cancer irradiation, have been elaborated. This resulted in the installation of a dedicated PET-facility at the experimental therapy unit at the heavy ion synchrotron SIS of GSI Darmstadt. Its main components are: (i) a double head PET-scanner integrated into the treatment site, (ii) a Monte Carlo code that is capable of predicting the β⁺-activity distributions from the treatment plan, and (iii) particular schemes of tomographic reconstruction that allow a verification before the next fraction of dose is applied.

In a series of in-beam PET-imaging experiments, where phantoms were irradiated with ¹²C ions, the sensitivity, the precision as well as the practical limits of the method have been investigated. First conclusions on the clinical relevance of the PET-techniques will be drawn from data obtained by ¹²C irradiations of realistic, tissue equivalent phantoms and of animals.
Supported by the BMBF under contract 06DR825 3.