Effects of nuclear interaction corrections and trichrome fragment spectra modelling on dose and linear energy transfer distributions in carbon ion radiotherapy

• Published in: Physics and imaging in radiation oncology 2024-01, Vol.29, p.100553-100553, Article 100553
• Main Authors: Bazani, Alessia, Brunner, Jacob, Russo, Stefania, Carlino, Antonio, Simon Colomar, Daniel, Ikegami Andersson, Walter, Ciocca, Mario, Stock, Markus, Fossati, Piero, Orlandi, Ester, Glimelius, Lars, Molinelli, Silvia, Knäusl, Barbara
• Format: Article
• Language: English
• Subjects: Carbon ion therapy; Fragment spectra; Linear energy transfer; Nuclear interaction correction; Original; Pencil beam; Trichrome modelling
• ISSN: 2405-6316; 2405-6316
• DOI: 10.1016/j.phro.2024.100553

•Predicting linear energy transfer needed nuclear interaction and trichrome modelling.•Rectified carbon dose and linear energy transfer did not affect clinical protocols.•Enhanced pencil beam modelling and Monte Carlo simulations agreed within 95%. Nuclear interaction correction (NIC) and trichrome fragment spectra modelling improve relative biological effectiveness-weighted dose (DRBE) and dose-averaged linear energy transfer (LETd) calculation for carbon ions. The effect of those novel approaches on the clinical dose and LET distributions was investigated. The effect of the NIC and trichrome algorithm was assessed, creating single beam plans for a virtual water phantom with standard settings and NIC + trichrome corrections. Reference DRBE and LETd distributions were simulated using FLUKA version 2021.2.9. Thirty clinically applied scanned carbon ion treatment plans were recalculated applying NIC, trichrome and NIC + trichrome corrections, using the LEM low dose approximation and compared to clinical plans (base RS). Four treatment sites were analysed: six prostate adenocarcinoma, ten head and neck, nine locally advanced pancreatic adenocarcinoma and five sacral chordoma. The FLUKA and clinical plans were compared in terms of DRBE deviations for D98%, D50%, D2% for the clinical target volume (CTV) and D50% in ring-like dose regions retrieved from isodose curves in base RS plans. Additionally, region-based median LETd deviations and global gamma parameters were evaluated. Dose deviations comparing baseRS and evaluation plans were within ± 1% supported by γ-pass rates over 97% for all cases. No significant LETd deviations were reported in the CTV, but significant median LETd deviations were up to 80% for very low dose regions. Our results showed improved accuracy of the predicted DRBE and LETd. Considering clinically relevant constraints, no significant modifications of clinical protocols are expected with the introduction of NIC + trichrome.