Arms positioning in post-mastectomy proton radiation:Feasibility and development of a new arms down contouring atlas

Background and purpose: Breast cancer patients receiving radiation are traditionally positioned with both arms up, but this may not be feasible or comfortable for all patients. We evaluated the treatment planning and positioning reproducibility differences between the arms up and arms down positions for patients receiving post-mastectomy radiation therapy (PMRT) using proton pencil beam scanning (PBS). Materials and methods: Ten PMRT patients who were scheduled to receive PBS underwent CT-based treatment planning in both an arms down and a standard arms up position. An arms down contouring atlas was developed for consistency in treatment planning. Treatment plans were performed on both scans. A Wilcoxon test was applied to compare arms up and arms down metrics across patients. Five patients received treatment in the arms-down position at our institution while others were treated with the arms up. Residual set-up errors were recorded for each patient's treatment fractions and compared between positions. Results: Target structure coverage remained consistent between the arms up and arms down positions. In regard to the OAR, the heart mean and maximum doses were statistically significantly lower in the arms up position versus the arms down position, however, the absolute differences were modest. Patients demonstrated similar setup errors, less than 0.5 mm differences, in all directions. Conclusions: PBS for PMRT in the arms down position appeared stable and reproducible compared to the traditional arms up positioning. The degree of OAR sparing in the arms down group was minimally less robust but still far superior to conventional photon therapy

Monte Carlo study of the potential reduction in out-of-field dose using a patient-specific aperture in pencil beam scanning proton therapy

This study is aimed at identifying the potential benefits of using a patientspecific aperture in proton beam scanning. For this purpose, an accurate Monte Carlo model of the pencil beam scanning (PBS) proton therapy (PT) treatment head at Massachusetts General Hospital (MGH) was developed based on an existing model of the passive double-scattering (DS) system. The Monte Carlo code specifies the treatment head at MGH with sub-millimeter accuracy. The code was configured based on the results of experimental measurements performed at MGH. This model was then used to compare out-of-field doses in simulated DS treatments and PBS treatments. For the conditions explored, the penumbra in PBS is wider than in DS, leading to higher absorbed doses and equivalent doses adjacent to the primary field edge. For lateral distances greater than 10 cm from the field edge, the doses in PBS appear to be lower than those observed for DS. We found that placing a patient-specific aperture at nozzle exit during PBS treatments can potentially reduce doses lateral to the primary radiation field by over an order of magnitude. In conclusion, using a patient-specific aperture has the potential to further improve the normal tissue sparing capabilities of PBS

EUropean Heliospheric FORecasting Information Asset 2.0

Aims: This paper presents a H2020 project aimed at developing an advanced space weather forecasting tool, combining the MagnetoHydroDynamic (MHD) solar wind and coronal mass ejection (CME) evolution modelling with solar energetic particle (SEP) transport and acceleration model(s). The EUHFORIA 2.0 project will address the geoeffectiveness of impacts and mitigation to avoid (part of the) damage, including that of extreme events, related to solar eruptions, solar wind streams, and SEPs, with particular emphasis on its application to forecast geomagnetically induced currents (GICs) and radiation on geospace. Methods: We will apply innovative methods and state-of-the-art numerical techniques to extend the recent heliospheric solar wind and CME propagation model EUHFORIA with two integrated key facilities that are crucial for improving its predictive power and reliability, namely (1) data-driven flux-rope CME models, and (2) physics-based, self-consistent SEP models for the acceleration and transport of particles along and across the magnetic field lines. This involves the novel coupling of advanced space weather models. In addition, after validating the upgraded EUHFORIA/SEP model, it will be coupled to existing models for GICs and atmospheric radiation transport models. This will result in a reliable prediction tool for radiation hazards from SEP events, affecting astronauts, passengers and crew in high-flying aircraft, and the impact of space weather events on power grid infrastructure, telecommunication, and navigation satellites. Finally, this innovative tool will be integrated into both the Virtual Space Weather Modeling Centre (VSWMC, ESA) and the space weather forecasting procedures at the ESA SSCC in Ukkel (Belgium), so that it will be available to the space weather community and effectively used for improved predictions and forecasts of the evolution of CME magnetic structures and their impact on Earth. Results: The results of the first six months of the EU H2020 project are presented here. These concern alternative coronal models, the application of adaptive mesh refinement techniques in the heliospheric part of EUHFORIA, alternative flux-rope CME models, evaluation of data-assimilation based on Karman filtering for the solar wind modelling, and a feasibility study of the integration of SEP models.</p

A path towards adaptive proton pencil beam scanning therapy

As technology advances, so does the quality of treatment offered to cancer patients. Proton therapy, and more specifically proton pencil beam scanning, is currently at the forefront of radiation therapy. Pencil beam scanning offers excellent tumor dose control as well as surrounding organs at risk sparing. Current treatment planning, however, is performed on a static image acquired before treatment. Naturally, this is not a proper representation of the actual patient on a daily basis. Thus, there is a need for adaptive radiation therapy, such as readjusting a given treatment plan based on the patient’s daily setup or a moving tumor location. In order to perform adaptive treatment delivery, appropriate imaging as well as an extremely fast, yet accurate, dose computation engine is needed. GEANT4 Monte Carlo simulations were performed in order to assess the imaging capabilities and limitations of a proton radiography detector, comparing them to conventional X-ray imaging. In parallel, a small form factor proton radiography system was designed based on available technologies. Thus, photonic bandgap fibers, a CMOS active pixel sensor, and Bicron scintillating fibers were evaluated for proton imaging purposes. The requisites and limitations of treatment planning for proton pencil beam scanning were further defined, from the acquisition of the treatment planning software’s beam model to the methodologies and treatment robustness. Based on this work, a simplified Monte Carlo algorithm was designed and implemented on the CPU architecture. This computation engine, GMC, was validated against physical observables and then compared to the treatment planning software dose calculation, as well as a ”full” Monte Carlo recomputation. Proton radiography showed poor spatial resolution but excellent density resolution when compared to X-ray radiography. This density resolution can be of importance when attempting to perform tumor tracking. The lower imaging dose associated with proton radiography is also of interest, especially in pediatric patients. Moreover, the use of a unique beam’s eye view could slightly improve the accuracy of treatment delivery. Photonic bangap fibers, as well as the specific CMOS active pixel sensor used in this work, did not yield promising results for proton imaging. Conversely, Bicron scintillating fibers proved to be suitable for the design of a proton radiography system, as both the individual particle’s position and energy could be acquired. The treatment planning software’s beam model is very simple, as compared to other modalities. However, the planning stage presented a few limitations, such as a lack of robustness analysis and issues related to spot placement. It was shown that both of these issues could be addressed with the use of a fast, yet accurate, dose computation engine. GMC was successfully implemented on the CPU architecture, and compared extremely well against actual pre-treatment QA measurements. The comparisons against the current algorithm of the treatment planning software and the full Monte Carlo engine matched the expectations for such an algorithm. The complementing work on proton imaging and fast dose computation algorithm lays a solid foundation to materializing pencil beam scanning adaptive radiotherapy. Future work will focus on generating the necessary synergy between the two systems in order to implement the tools in the clinical setting

Ion radiography as a tool for patient set-up & image guided particle therapy: a Monte Carlo study

This study investigate the use of ion radiography as a tool for patient set-up and tumor tracking capabilities for image guided particle therapy (IGPT) using Monte Carlo simulations. One pediatric, two lung and one liver cancer patients were considered in this study. For each patient, 230 and 330 MeV proton, and 500 MeV/nucleon carbon ion pencil beams were simulated through their computed tomography (CT) data set using GEANT4.9.0. Energy, position and direction cosines of each particle were recorded in front and behind the patient. Ion radiographs were subsequently reconstructed using a dedicated in-house software. The image quality was assessed by evaluating the contrast-to-noise ratio of the tumor and its surrounding tissue. In the lung and liver cases, each CT phase of the breathing cycle was treated individually and dynamic sequences were later produced to appreciate tumor motion. Reconstructed radiographs show high spatial resolution. This allows for excellent imaging capabilities in pediatric patients, comparable to X-ray imaging at a fraction of the imaging dose. There is clear visualization of the tumor edges in the lung due to the great contrast-to-noise ratio between the tumor and its surrounding tissues; tumor motion is observed and comparable to 4D CT data thus allowing for on-line tumor tracking during ion radiotherapy. Conversely, tumor edge detection is difficult in liver, and fiducial markers are required to attempt indirect tumor tracking for IGPT. Ion radiographs with high spatial resolution can be generated using the PR-creator software resulting in pediatric patient set-up capabilities at a fraction of the current imaging dose, as well as the capacity to track moving targets in order to achieve IGPT