A dose determination procedure by PET monitoring in proton therapy

The selective energy deposition of hadrontherapy has led to a growing interest in quality assurance techniques of dose delivery. In particular, the interest in Positron Emission Tomography (PET) as a tool for treatment verification in proton therapy has become widespread in the last years and several research groups worldwide are currently investigating its clinical implementation. The aim of this work is to present an unfolding procedure which, starting from the β⁺ activity distribution of ¹¹C measured with PET, leads to an estimation of the delivered dose allowing a direct comparison with the planned one. The foundation of the proposed method is a filtering approach which describes the induced activity as a convolution of the dose distribution with a well defined filter function. As a solution we propose a method based on the Tikhonov theory which imposes a regularization constraint to the solution. Preliminary tests have been performed with Monte Carlo (MC) simulated data on homogeneous and inhomogeneous phantoms, showing robustness and spatial accordance between the numerically reconstructed dose and the simulated one.