Thesis title: Inter-fractional monitoring in Particle Therapy treatments with 12C ions exploiting the detection of secondary particles: simulation studies and clinical trial results at the CNAO facility
In Particle Therapy morphological variations occurring within the treatment delivery may significantly modify the actual absorbed dose with respect to that one calculated at planning stage, affecting the treatment efficacy and the enhancing the Normal Tissue Complication Probability. In the clinical practice at CNAO (Centro Nazionale di Adroterapia Oncologica, Pavia, Italy) a mid-treatment control CT is scheduled for patients pathologies in which significant toxicities or tumour volume modifications are expected. In these cases, the treatment is re-planned if the detected variations are significantly affecting the dose absorbed by the PTV. The afore-mentioned strategy, cannot exclude that some of the patients that are not monitored may experience a variation resulting into an unwanted dose absorption inside the normal tissues and the organs at risk, together with an underdosage of the target volume. Furthermore, the monitored patients in which no change is observed receive an unnecessary additional dose from the imaging.
The Dose Profiler, developed in the framework of the INSIDE collaboration, is a scintillating fiber-based tracker detector designed to monitor 12C ions treatments reconstructing the large-angle charged particles produced by the primary beam fragmentation. As the fragments yield is correlated with the tissue density, morphological variations can be identified comparing the reconstructed 3D spatial distributions of the fragments emission points in different fractions, with the aim of providing an experimental reliable criterium for scheduling a re-evaluation CT only when needed. The Dose Profiler is currently operating at CNAO in the context of a clinical trial (ClinicalTrials.gov Identifier: NCT03662373) started in 2019.
This thesis aims to evaluate the Dose Profiler capability and sensitivity in detecting morphological changes arising in pathologies of the neck-head district using the data collected during the clinical trial. After each monitored fraction (for a total of ~ 5 treatment sessions per patient), the 3D image of the fragments emission positions is reconstructed back-projecting the tracks detected in the DP towards the patient, and then compared against the one obtained in the first fraction. The applicability of such technique in the clinical routine and its limitation will be discussed analysing in detail all the collected clinical cases.