Feasibility of Proton Range Estimation with Prompt Gamma Imaging in Proton Therapy of Lung Cancer: Monte Carlo Study

• Published in: Journal of medical physics Vol. 49; no. 4; pp. 531 - 538
• Main Authors: Rohollahpour, Elham, Ahangari, Hadi Taleshi
• Format: Journal Article
• Language: English
• Published: India Wolters Kluwer - Medknow 01.10.2024; Medknow Publications and Media Pvt. Ltd; Medknow Publications & Media Pvt. Ltd; Wolters Kluwer Medknow Publications
• Edition: 2
• Subjects: anthropomorphic phantom; Cancer; Care and treatment; Energy spectra; Estimation; Feasibility studies; Gamma emission; Graphics software; Health aspects; In vivo methods and tests; Lung cancer; Medical imaging; Monitoring; Monte Carlo method; Monte Carlo simulation; Nuclear interactions; Oncology, Experimental; Original; Original Article; Pencil beams; Physiological aspects; Polymethyl methacrylate; Polymethylmethacrylate; prompt gamma imaging; Proton beams; proton range estimation; Protons; Radiation Oncology Physics; Radiation therapy; Real time; Simulation methods; Therapy; Torso; Tumors; lung cancer; Anthropomorphic phantom; prompt gamma imaging; Monte Carlo simulation; proton range estimation
• ISSN: 0971-6203; 1998-3913
• DOI: 10.4103/jmp.jmp_74_24

Context: Using prompt gamma (PG) ray is proposed as a promising solution for in vivo monitoring in proton therapy. Despite significant and diverse approaches explored over the past two decades, challenges still persist for more effective utilization. Aims: The feasibility of estimating proton range with PG imaging (PGI) as an online imaging guide in an anthropomorphic phantom with lung cancer was investigated through GATE/GEANT4 Monte Carlo simulation. Setting and Design: Once the GATE code was validated for use as a simulation tool, the gamma energy spectra of NURBS-based cardiac-torso (NCAT) and polymethyl methacrylate phantoms, representing heterogeneous and homogeneous phantoms respectively, were compared with the gamma emission lines known in nuclear interactions with tissue elements. A 5-mm radius spherical tumor in the lung region of an NCAT phantom, without any physiological or morphological changes, was simulated. Subjects and Methods: The proton pencil beam source was defined as a function of the tumor size to encompass the tumor volume. The longitudinal spatial correlation between the proton dose deposition and the distribution of detected PG rays by the multi-slit camera was assessed for proton range estimation. The simulations were conducted for both 108 and 109 protons. Results: The deviation between the proton range and the range estimated by PGI following proton beam irradiation to the center of the lung tumor was determined by evaluating the longitudinal profiles at the 80% fall-off point, measuring 1.9 mm for 109 protons and 4.5 mm for 108 protons. Conclusions: The accuracy of proton range estimation through PGI is greatly influenced by the number of incident protons and tissue characteristics. With 109 protons, it is feasible to utilize PGI as a real-time monitoring technique during proton therapy for lung cancer.