Ricerc@Sapienza

The particle therapy (PT) is a technique for cancer treatment that exploits hadron beams, mostly protons and carbon ions. The characteristic profile of the energy deposition along the beam track, with the peculiar maximum at the end of the range (Bragg Peak) that is moved inside the patient with the increase of the beam energy, allows this techique to precisely deposit the dose on the tumor volume and to spare the surrounding healthy tissue. Due to this spatial selectivity in dose deposition, a critical issue is the monitoring of the beam range so to check the correct dose delivery to the tumor and surrounding tissues. The information needed to use the correct patterns of beam direction, energies and intensities is provided by the planning CT. Possible changes in the beam range are often due to the morphological changes of the patient tissue with respect to the planning imaging along the beam track during the entire treatment time (order of thirty fractions in a two monthes period).
A innovative tracking device, named Dose Profiler (DP) for inter-fractional monitoring in pencil beam carbon ion therapy has been designed and built by our group, and is now in clinical testing phase at the CNAO (Centro Nazionale di Adroterapia Oncologica) center in Pavia. Its scope is to quantitatively molitor the inter-fractional motion so that a re-planning imaging CT can be done in case of detected changes.
The DP detects and reconstruct the direction of the secondary charged particles (mainly protons) produced by beam interactions in the patient tissue and excaping the patient. The point of closest approach of the tracked protons with the emitting pencil beam provides the emission point of the secondary.
The 3D map of the proton emission points provides the info used to monitor the patient morphology. Different sets of statistical analysis of the 3D mapos coming from subsequent treatments are studied to design a statistical robust method to assess the moment for a re-planning CT