Étude Monte Carlo de l’impact de la tomodensitométrie multiénergie sur la précision du calcul de dose en protonthérapie
Proton therapy is a cancer treatment modality that has the potential to target tumours more accurately than conventional radiotherapy. However, current clinical practice intro- duces an uncertainty on proton beam ranges that impairs the benefits of proton therapy over traditional methods. Indeed, the lack of accuracy on the prediction of protons’ path inside patients forces the application of safety margins around target volumes, and this at the cost of a larger volume of healthy tissues being irradiated. The purpose of this work is to study the potential of multi-energy computed tomography (MECT) to reduce proton beam range uncertainties. First, a novel method to characterize human tissues with MECT is developed. The method, called eigentissue decomposition (ETD) aims to extract the el- emental composition and density of human tissues in order to accurately calculate proton beams transport with Monte Carlo simulations. The ETD method is further adapted to the context of noise in CT images using a Bayesian estimator. Then, a clustering approach based on the k-means algorithm is developed in order to allow the implementation of the ETD method in a Monte Carlo algorithm. Finally, these methods are used to evaluate the impact of MECT on proton range uncertainties in a ground truth humanoid geometry. Dose distributions are compared to quantify the performance of MECT over conventional meth- ods. Results indicate that MECT used with the ETD method allows to reduce proton range uncertainties from 1.51% to 0.86%. The study suggests that MECT has the potential to improve the accuracy of proton therapy and therefore its benefits over conventional radio- therapy. Indeed, improved accuracy in dose calculation is associated with an increase in treatments’ success rate, a decrease in secondary effects as well as a diminution of cancer recurrence.
Méthode Monte Carlo Tomodensitométrie multiénergie Radiation oncology Proton therapy Monte Carlo simulations Dose calculation X-ray Computed tomography Multi-energy computed tomography Photon-counting CT