Investigate prompt gamma profiles using a collimator-based camera for in-vivo monitoring of distal dose and tumour localisation in proton therapy of non-small cell lung cancer: a Monte Carlo simulation study

Abstract

Abstract Introduction: Lung cancer ranks high among the causes of mortality in cancer patients, as per the most recent World Health Organization report. Proton therapy offers a precise approach to treating lung cancer by delivering protons with high accuracy to the targeted site. However, inaccuracies in proton delivery can lead to increased toxicity in healthy tissues. This study aims to investigate the correlation between proton beam dose profiles in lung tumours and the scattered gamma particles. Material and methods: The study utilised the Gate simulation software to simulate proton beam radiation and an imaging system for prompt gamma imaging during proton therapy. An anthropomorphic Non-uniform rational B-spline (NURBS) cardiac and torso (NCAT) phantom was employed to replicate lung tumours of various sizes. The imaging system comprised a multi-slit collimation system, CsI(Tl) scintillator arrays and a multichannel data acquisition system. Simulations were conducted to explore the relationship between prompt gamma detection and proton range for different tumour sizes. Results: Following 60 MeV proton irradiation of the NCAT phantom, the study examined the gamma energy spectrum, identifying peak intensities at energies of 2.31, 3.8, 4.44, 5.27 and 6.13 MeV. Adjustments to the proton beam source tailored to tumour sizes achieved a coverage rate of 98%. Optimal energies ranging from 77 to 91.5 MeV were determined for varying tumour volumes, supported by dose distribution profiles and prompt gamma distribution illustrations. Discussion: The study evaluated the viability of utilising 2D gamma imaging with a multi-slit collimator scintillation camera for real-time monitoring of dose delivery during proton therapy for lung cancer. The findings indicated that this method is most suitable for small lung tumours (radius ≤ 12 mm) due to reduced gamma emission from larger tumours. Conclusion: While the study demonstrates promising results in range estimation using prompt gamma particles, challenges were encountered in accurately estimating large tumours using this method.