Author:
Moglioni Martina,Kraan Aafke Christine,Baroni Guido,Battistoni Giuseppe,Belcari Nicola,Berti Andrea,Carra Pietro,Cerello Piergiorgio,Ciocca Mario,De Gregorio Angelica,De Simoni Micol,Del Sarto Damiano,Donetti Marco,Dong Yunsheng,Embriaco Alessia,Fantacci Maria Evelina,Ferrero Veronica,Fiorina Elisa,Fischetti Marta,Franciosini Gaia,Giraudo Giuseppe,Laruina Francesco,Maestri Davide,Magi Marco,Magro Giuseppe,Malekzadeh Etesam,Marafini Michela,Mattei Ilaria,Mazzoni Enrico,Mereu Paolo,Mirandola Alfredo,Morrocchi Matteo,Muraro Silvia,Orlandi Ester,Patera Vincenzo,Pennazio Francesco,Pullia Marco,Retico Alessandra,Rivetti Angelo,Da Rocha Rolo Manuel Dionisio,Rosso Valeria,Sarti Alessio,Schiavi Angelo,Sciubba Adalberto,Sportelli Giancarlo,Tampellini Sara,Toppi Marco,Traini Giacomo,Trigilio Antonio,Valle Serena Marta,Valvo Francesca,Vischioni Barbara,Vitolo Viviana,Wheadon Richard,Bisogni Maria Giuseppina
Abstract
Morphological changes that may arise through a treatment course are probably one of the most significant sources of range uncertainty in proton therapy. Non-invasive in-vivo treatment monitoring is useful to increase treatment quality. The INSIDE in-beam Positron Emission Tomography (PET) scanner performs in-vivo range monitoring in proton and carbon therapy treatments at the National Center of Oncological Hadrontherapy (CNAO). It is currently in a clinical trial (ID: NCT03662373) and has acquired in-beam PET data during the treatment of various patients. In this work we analyze the in-beam PET (IB-PET) data of eight patients treated with proton therapy at CNAO. The goal of the analysis is twofold. First, we assess the level of experimental fluctuations in inter-fractional range differences (sensitivity) of the INSIDE PET system by studying patients without morphological changes. Second, we use the obtained results to see whether we can observe anomalously large range variations in patients where morphological changes have occurred. The sensitivity of the INSIDE IB-PET scanner was quantified as the standard deviation of the range difference distributions observed for six patients that did not show morphological changes. Inter-fractional range variations with respect to a reference distribution were estimated using the Most-Likely-Shift (MLS) method. To establish the efficacy of this method, we made a comparison with the Beam’s Eye View (BEV) method. For patients showing no morphological changes in the control CT the average range variation standard deviation was found to be 2.5 mm with the MLS method and 2.3 mm with the BEV method. On the other hand, for patients where some small anatomical changes occurred, we found larger standard deviation values. In these patients we evaluated where anomalous range differences were found and compared them with the CT. We found that the identified regions were mostly in agreement with the morphological changes seen in the CT scan.