Annelie Johansson, Camilo J. Sanz Freire, Pedro M. Collado Chamorro, Susana Pérez Echagüen, Gustavo A. Ossola Lentati and Alejandro Sánchez-Crespo
Purpose: To develop a framework for biologically-optimized routine intensity modulated radiotherapy (IMRT) treatment plans based on 18F-fluoro-deoxy-glucose (FDG)-Positron Emission Tomography (PET)/Computed Tomography imaging.
Methods and materials: The dose-planning FDG-PET images are first corrected for partial volume effect using an iterative algorithm with a noise suppression filter. Thereafter, the FDG-uptake is used for transforming the delineated clinical target volume (CTV) into a set of biological planning target volumes (bPTV). This is done with an optimization algorithm that groups pixel values with the objective of maximizing the FDG-uptake variance between bPTV. The resulting average FDG pixel intensity within each bPTV, together with a tumor control probability (TCP) function, are used to obtain the prescribed dose to each bPTV that maximize the total TCP, using dose limits to the organs at risk (OAR) as constraints. The accuracy of this method was tested on a phantom. Additionally, this framework was also tested on five patients with head-neck cancer, in a retrospective clinical trial.
Results: The extension of the obtained bPTV and their activity concentration showed good agreement with the true FDG distribution in the phantom. All patients planned using the presented methodology achieved a notable increase in TCP, compared to the standard IMRT plans.
Conclusions: FDG-PET together with this framework can be used to biologically optimize IMRT to individualize cancer treatment.
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