Program Information

TPS_PET - A TPS-Based Approach for In-Vivo Dose Verification with PET in Proton Therapy

K Frey

K Frey^1,2*, J Bauer^2,3, D Unholtz^2,3, C Kurz^2,3, M Kraemer⁴, T Bortfeld⁵, K Parodi^1,2,3, (1) Ludwig-Maximilian University, Munich, Germany (2) Heidelberg Ion-Beam Therapy Centre, Heidelberg, Germany, (3) University Hospital, Heidelberg, Germany, (4) GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt, Germany ,(5) Massachusetts General Hospital, Boston, MA

TH-C-144-6 Thursday 10:30AM - 12:30PM Room: 144

Purpose:
PET (positron-emission tomography)-based treatment verification uses the irradiation-induced tissue activation inside the patient. The comparison between measured PET data and corresponding predictions, obtained under the assumption of a correct treatment delivery, is clinically used to validate the proton beam range and the dose application. In contrast to the typically performed time-consuming Monte Carlo (MC) simulations, TPS_PET is introduced as a new approach using the algorithms of the clinical treatment planning system (TPS). The calculation yields β⁺-emitter distributions being fully consistent with the treatment planning dose.

Methods:
Positron-emitter basic data are obtained from the convolution of TPS reference depth-dose profiles in water with reaction-channel dependent filter functions. This database and fast post-processing enables the calculation of three-dimensional β⁺-emitter distributions based on the same algorithms as used for the planning of the treatment dose. Validation of this TPS_PET concept is performed in phantom and patient studies against MC simulations and one-dimensional filtering of three-dimensional dose distributions.

Results:
TPS and MC are based on intrinsically different calculation models, which affect dose and positron-emitter density predictions. Especially in the case of small fields and tissue inhomogeneities, pronounced limitations of the one-dimensional filtering of three-dimensional dose distributions are observed, which can be overcome by TPS_PET. In the case of extended patient treatment, good agreement is achieved between TPS_PET and MC.

Conclusion:
In contrast to previously introduced methods, TPS_PET provides a faster implementation and is not limited by sensitivity to lateral field extensions. The calculations are performed without modifying the TPS pencil beam algorithm, resulting in positron-emitter predictions, which are consistent to the planned treatment dose. All these aspects confirm TPS_PET as a promising alternative to full-blown MC. The method can be integrated in existing TPS to enable PET-based treatment verification in the daily clinical routine of proton therapy.

Contact Email: