3D printed 2D range modulators preserve radiation quality on a microdosimetric scale in proton and carbon ion beams. (May 2023)

• Record Type: Journal Article
• Authors: Barna, Sandra; Meouchi, Cynthia; Resch, Andreas Franz; Magrin, Giulio; Georg, Dietmar; Palmans, Hugo
• Is Part Of: Radiotherapy and oncology. Volume 182(2023)
• Publication Date: 2023-05
• Subjects: Particle therapy -- 2D range modulator -- 2D ripple filter -- Microdosimetry -- Monte Carlo simulation; Oncology -- Periodicals; Radiotherapy -- Periodicals; Tumors -- Periodicals; Medical Oncology -- Periodicals; Neoplasms -- radiotherapy -- Periodicals; Radiotherapy -- Periodicals; Radiothérapie -- Périodiques; Cancérologie -- Périodiques; Tumeurs -- Périodiques; Electronic journals; 616.9940642
• DOI: 10.1016/j.radonc.2023.109525
• Languages: English
• ISSNs: 0167-8140

Abstract

Highlights: 3D printed 2D/3D range modulators (2D/3DRM) offer advantages for light ion beam therapy, also in combination with pencil-beam scanning (PBS). We designed 2DRMs with Monte Carlo simulations and validated them on a dosimetric as well as on a microdosimetric scale for both H and C12 beams. The equivalence of using a single spot vs. a larger plan delivered via PBS with an appropriate 2DRM based on microdosimetric spectra is shown. Abstract: Introduction: Particle therapy using pencil beam scanning (PBS) faces large uncertain- ties related to ranges and target motion. One possibility to improve existing mitigation strategies is a 2D range modulator (2DRM). A 2DRM offers faster irradiation times by reducing the number of layers and spots needed to create a spread-out Bragg peak. We have investigated the impact of 2DRM on microdosimetric spectra measured in proton and carbon ion beams. Materials and Methods: Two 2DRMs were designed and 3D printed, one for. 124.7 MeV protons and one for 238.6 MeV/u carbon ions. Their dosimetric validation was performed using Roos and PinPoint ionization chamber and EBT3 films. Monte Carlo simulations were done using GATE. A silicon-based solid-state microdosimeter was used to collect pulse-height spectra along three depths for two irradiation modalities, PBS and a single central beam. Results: For both particle types, the original pin design had to be optimized via GATE simulations. The difference between the R80 of the simulated and measured depth dose curve was 0 . 1 mm. The microdosimetric spectra collected with the two irradiation modalities overlap well. Their mean lineal energy values differ over all positions by 5 . 2 % for the proton 2DRM and 2 . 1 % for the carbon ion 2DRM. Conclusion: Radiation quality in terms of lineal energy was independent of the irradiation method. This supports the current approach in reference dosimetry, where the residual range is chosen as a beam quality index to select stopping power ratios.