Technical note: In silico benchmarking of the linear energy transfer‐based functionalities for carbon ion beams in a commercial treatment planning system

Abstract

Background:The increasing number of studies dealing with linear energy transfer (LET)-based evaluation and optimization in the field of carbon ion radiotherapy (CIRT) indicates the rising demand for LET implementation in commercial treatment planning systems (TPS). Benchmarking studies could play a key role in detecting (and thus preventing) computation errors prior implementing such functionalities in a TPS. Purpose: This in silico study was conducted to benchmark the following two LET-related functionalities in a commercial TPS against Monte Carlo simulations: (1) dose averaged LET (LET d ) scoring and (2) physical dose filtration based on LET for future LET-based treatment plan evaluation and optimization studies. Methods: The LET d scoring and LET-based dose filtering (in which the deposited dose can be separated into the dose below and above the user specified LET threshold) functionalities for carbon ions in the research version RayStation (RS) 9A-IonPG TPS (RaySearch Laboratories, Sweden) were benchmarked against GATE/Geant4 simulations. Pristine Bragg peaks (BPs) and cuboid targets, positioned at different depths in a homogeneous water phantom and a setup with heterogeneity were used for this study. Results: For all setups (homogeneous and heterogeneous), the mean absolute (and relative) LET d difference was less than 1 keV/μm (3.5%) in the plateau and target and less than 2 keV/μm (8.3%) in the fragmentation tail. The maximum local differences were 4 and 6 keV/μm, respectively. The mean absolute (and relative) physical dose differences for both low-and high-LET doses were less than 1 cGy (1.5%) in the plateau, target and tail with a maximum absolute difference of 2 cGy. Conclusions: No computation error was found in the tested functionalities except for LET d in lateral direction outside the target, showing the limitation of the implemented monochrome model in the tested TPS version.

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

“…Also, this change in particle type and LET d resulted in a minor median increase (<1%) of D 50% in the target region. The observed deviations in the clinical plans confirm the previous non-clinical examinations in the frame of the algorithm development and phantom studies [28] .…”

Investigation on the physical dose filtered by linear energy transfer for treatment plan evaluation in carbon ion therapy

“…The LET‐based dose filtration functionality of RayStation 9A‐IonPG (Non‐clinical license build), benchmarked in a recent study, 29 was utilized to score the $$\textrm {D}_{&gt;\textrm {L}_{\textrm {thr}}}$$. The functionality provides physical dose distributions deposited by particles with an LET lower or higher than a user specified LET threshold (Figure ).…”

“…The LET-based dose filtration functionality of RayStation 9A-IonPG (Non-clinical license build), benchmarked in a recent study, 29 was utilized to score the D >L thr .…”

Dose averaged linear energy transfer optimization for large sacral chordomas in carbon ion therapy

“…This quantity is reported as LET d in water, normalized to unit density. 24 The implementation specifications of LET d optimization is described in another work. 22 In order to increase the LET d in the CTV-HD, the "minimum LET d " optimization function (L min ) of the TPS was utilized for the seven PTV-HD fractions.…”