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

Background: Carbon ion beams are well accepted as densely ionizing radiation with a high linear energy transfer (LET). However, the current clinical practice does not fully exploit the highest possible dose-averaged LET (LET) and, consequently, the biological potential in the target. This aspect becomes worse in larger tumors for which inferior clinical outcomes and corresponding lower LET was reported.

First microdosimetric measurements with a tissue-equivalent proportional counter at the MedAustron ion-beam therapy facility.

The aim of this work is to present the first microdosimetric spectra measured with a miniaturised tissue-equivalent proportional counter in the clinical environment of the MedAustron ion-beam therapy facility. These spectra were gathered with a 62.4-MeV proton beam and have been compared with microdosimetric spectra measured in the 62-MeV clinical proton beam of the CATANA beam line.

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

Background: Large tumor size has been reported as a predicting factor for inferior clinical outcome in carbon ion radiotherapy (CIRT). Besides the clinical factors accompanied with such tumors, larger tumors receive typically more low linear energy transfer (LET) contributions than small ones which may be the underlying physical cause. Although dose averaged LET is often used as a single parameter descriptor to quantify the beam quality, there is no evidence that this parameter is the optimal clinical predictor for the complex mixed radiation fields in CIRT.

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

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.

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

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 ) scoring and (2) physical dose filtration based on LET for future LET-based treatment plan evaluation and optimization studies.

Small field proton irradiation for in vivo studies: Potential and limitations when adapting clinical infrastructure.

Purpose: To evaluate the dosimetric accuracy for small field proton irradiation relevant for pre-clinical in vivo studies using clinical infrastructure and technology. In this context additional beam collimation and range reduction was implemented.

Methods And Materials: The clinical proton beam line employing pencil beam scanning (PBS) was adapted for the irradiation of small fields at shallow depths.

Accelerating and improving radiochromic film calibration by utilizing the dose ratio in photon and proton beams.

Purpose: Radiochromic films are versatile 2D dosimeters with high-resolution and near tissue equivalence. To assure high precision and accuracy, a time-consuming calibration process is required. To improve the time efficiency, a novel calibration method utilizing the ratio of the same dose profile measured at different monitor units (MUs) is introduced and tested in a proton and photon beam.

Technical note: Impact of beamline-specific particle energy spectra on clinical plans in carbon ion beam therapy.

Purpose: The Local Effect Model version one (LEM I) is applied clinically across Europe to quantify the relative biological effectiveness (RBE) of carbon ion beams. It requires the full particle fluence spectrum differential in energy in each voxel as input parameter. Treatment planning systems (TPSs) use beamline-specific look-up tables generated with Monte Carlo (MC) codes.

Technical note: Experimental determination of the effective point of measurement of the PTW-31010 ionization chamber in proton and carbon ion beams.

Purpose: The accurate knowledge of the effective point of measurement (P ) is particularly important for measurements in proximity to high dose gradients such as in the distal fall-off of particle beams. For plane-parallel ionization chambers (ICs), P is well known and located at the center of the inner surface of the entrance window. For cylindrical ICs, P is shifted from the chamber's center toward the beam source.

The practical radius of a pencil beam in proton therapy.

The central Gaussian shaped high dose region of a pencil beam (PB) in light ion beam therapy (LIBT) is enveloped by a low dose region causing non-negligible field size effects and impairs the dose calculation accuracy considerably if the low dose envelope is not well modeled. The purpose of this study was to calculate the practical radius, R, at which a PB does not influence a field more than a certain accuracy level. Lateral dose profiles of proton beams in water were simulated using GATE/Geant4.

Long-term stable optical cavity for special relativity tests in space: erratum.

We incorrectly cited a maximum acceleration sensitivity of the rigidly-mounted cavity of 2.5 × 10 1/(m s). The correct coupling factor is a factor of 100 smaller: 2.

Dose- rather than fluence-averaged LET should be used as a single-parameter descriptor of proton beam quality for radiochromic film dosimetry.

Purpose: The dose response of Gafchromic EBT3 films exposed to proton beams depends on the dose, and additionally on the beam quality, which is often quantified with the linear energy transfer (LET) and, hence, also referred to as LET quenching. Fundamentally different methods to determine correction factors for this LET quenching effect have been reported in literature and a new method using the local proton fluence distribution differential in LET is presented. This method was exploited to investigate whether a more practical correction based on the dose- or fluence-averaged LET is feasible in a variety of clinically possible beam arrangements.

A GATE/Geant4 beam model for the MedAustron non-isocentric proton treatment plans quality assurance.

Purpose: To present a reference Monte Carlo (MC) beam model developed in GATE/Geant4 for the MedAustron fixed beam line. The proposed model includes an absolute dose calibration in Dose-Area-Product (DAP) and it has been validated within clinical tolerances for non-isocentric treatments as routinely performed at MedAustron.

Material And Methods: The proton beam model was parametrized at the nozzle entrance considering optic and energy properties of the pencil beam.

Evaluation of electromagnetic and nuclear scattering models in GATE/Geant4 for proton therapy.

Purpose: The dose core of a proton pencil beam (PB) is enveloped by a low dose area reaching several centimeters off the central axis and containing a considerable amount of the dose. Adequate modeling of the different components of the PB profile is, therefore, required for accurate dose calculation. In this study, we experimentally validated one electromagnetic and two nuclear scattering models in GATE/Geant4 for dose calculation of proton beams in the therapeutic energy window (62-252 MeV) with and without range shifter (RaShi).

Monte Carlo proton dose calculations using a radiotherapy specific dual-energy CT scanner for tissue segmentation and range assessment.

Proton beam ranges derived from dual-energy computed tomography (DECT) images from a dual-spiral radiotherapy (RT)-specific CT scanner were assessed using Monte Carlo (MC) dose calculations. Images from a dual-source and a twin-beam DECT scanner were also used to establish a comparison to the RT-specific scanner. Proton ranges extracted from conventional single-energy CT (SECT) were additionally performed to benchmark against literature values.

A Monte-Carlo study to assess the effect of 1.5 T magnetic fields on the overall robustness of pencil-beam scanning proton radiotherapy plans for prostate cancer.

Combining magnetic-resonance imaging (MRI) and proton therapy (PT) using pencil-beam scanning (PBS) may improve image-guided radiotherapy. We aimed at assessing the impact of a magnetic field on PBS-PT plan quality and robustness. Specifically, the robustness against anatomical changes and positioning errors in an MRI-guided scenario with a 30 cm radius 1.

Benchmarking GATE/Geant4 for O ion beam therapy.

Oxygen ([Formula: see text]) ions are a potential alternative to carbon ions in ion beam therapy. Their enhanced linear energy transfer indicates a higher relative biological effectiveness and a reduced oxygen enhancement ratio. Due to the limited availability of [Formula: see text] ion beams, Monte Carlo (MC) transport codes are important research tools for investigating their potential.

Comparing cone-beam CT intensity correction methods for dose recalculation in adaptive intensity-modulated photon and proton therapy for head and neck cancer.

Background: Adaptive intensity-modulated photon and proton radiotherapy (IMRT and IMPT) of head and neck (H&N) cancer requires frequent three-dimensional (3D) dose calculation. We compared two approaches for dose recalculation on the basis of intensity-corrected cone-beam (CB) x-ray computed tomography (CT) images.

Material And Methods: For nine H&N tumor patients, virtual CTs (vCT) were generated by deformable image registration of the planning CT (pCT) to the CBCT.