Nedstack fuel cell technology (Netherlands)

PurposeTo systematically compare fully automated planning for 36-field discrete proton arc therapy (36PAT) with: (1) intensity-modulated proton therapy (IMPT) with 4- and 6-field clinical beam-angle class solutions (4CS, 6CS), (2) IMPT with patient-specific, computer-optimized beam-angle configurations with 6, 8 or 10 fields (6BAO, 8BAO, 10BAO), and (3) 36-field equiangular ‘‘Utopia’’ IMPT (36Utopia; total focus on dosimetric quality, no delivery time considerations) for oropharyngeal cancer patients.Materials and MethodsAll automated plan generations were performed with Erasmus-iCycle. An energy layer (EL) reduction algorithm was developed in Erasmus-iCycle to balance plan quality with delivery time in discrete PAT planning. Patient-tailored beam-angle configurations for BAO plans were obtained with the earlier published iCycle-pBAO. In 36Utopia plans, no EL reductions were applied. While beam configurations varied among approaches, all final plans were automatically generated using the published wish-list driven SISS-MCO optimizer with dosimetry-based sparsity-induced spot selection (SISS), followed by multi-criterial spot weight optimization (MCO) and resulting in Pareto-optimality in spot weights. The same wish-list for all delivery approaches prevented planning bias across approaches.Results36PAT plans achieved organs at risk (OAR) doses and normal tissue complication probability (NTCP) approaching 36Utopia plans. Relative to CS plans, 36PAT plans reduced normal tissue dose, decreasing xerostomia and dysphagia NTCPs. Compared to 4CS, 36PAT reduced summed NTCPs for grade 2 toxicity by 6.1%-point (P = .002) and grade 3 by 2.1%-point (P = .002). For 6CS, reductions were 4.7%-point (P = .002) and 1.2%-point (P = .01), respectively. 36PAT plans also outperformed BAO plans with 6 and 8 fields but were comparable to 10BAO in OAR doses and NTCPs for similar EL numbers and Monitor Units (MU).ConclusionPAT demonstrated superior dosimetric quality over clinical class solutions for oropharyngeal cancer and approached Utopia. Ten-field IMPT with personalized beam angles could be an alternative to 36-field PAT with similar expected toxicity, ELs and MUs, but a lower number of fields.

Ellipsoid tumour models are used to approximate the tumour volume of uveal melanomas, as the conventionally used ultrasound does not provide a three-dimensional visualization of the tumour. However, these models are a simplification of the actual tumour geometry. The aim of this study was to determine to what extent several of these frequently used ellipsoid tumour models accurately describe uveal melanoma volume. Tumours were delineated on contrast-enhanced T1-weighted MRI for 70 uveal melanoma patients. The MRI-delineated volume was compared with three ellipsoid models, which used two-dimensional measurements such as thickness and basal diameters as input: half ellipsoids with round (Vroundbase) or oval base (Vovalbase) and a paraboloid consisting of two parts, also incorporating the curvature of the eye wall (Vtwoparts). Statistically significant relative differences between MRI-delineated and model volume of 53 ± 32% (Vroundbase), 26 ± 24% (Vovalbase) and 15 ± 24% (Vtwoparts) were observed (p < 0.001). Tumour volume and shape did not influence the difference between the model volumes and MRI-delineated tumour volume. All tumour models result in considerable systematic overestimations of tumour volume, with large variations in overestimation between patients. Adding the perpendicular basal diameter to the model decreases this variation. Although ellipsoid tumour models have been shown to be valuable on a group level, they should be used with caution for individual patients.

In online-adaptive proton therapy planning based on cone beam computed tomography (CBCT), CT number errors can pose challenges. We propose an approach for coping with CT number uncertainties by increasing range robustness settings (RRS) in online-adaptive planning. This was compared to our trigger-based offline (TB-Offline) adaptive approach, and to daily replanning using in-room CT-on-rails (CTOR). For 23 head-and-neck cancer patients, a CTOR and CBCT were acquired in a single fraction. CTOR contours were copied rigidly onto the CBCT. CBCT-based plans were generated with 3, 6, 8, 10, and 12% RRS, each with 1mm setup-RS, followed by a forward dose calculation on the reference CTOR. This was compared to dose distributions from our TB-Offline approach (3mm/3% SRS/RRS), also recomputed on the CTOR. Coverage (voxelwise-minimum) of the primary clinical target volume (CTV7000) and elective lymph nodes (CTV5425) and grade≥II normal tissue complication probabilities were compared between strategies. When going from RRS=3% to RRS=10%, the population 90th percentiles of CTV5425 V94% improved from 89.6% to 96.4%, and CTV7000 V94% from 92.8% to 96.4%. Substantial coverage loss (V94%<95%) with CBCT-based online adaptive and RRS=10% was observed in 1/23 evaluated patients for CTV7000 and 2/23 for CTV5425. This was an improvement compared to 3/23 and 4/23 with TB-Offline. Moreover, for RRS=10% the average risk of xerostomia improved by 2.4 percentage point compared to TB-Offline. Robust optimization with increased range robustness settings effectively mitigated dose degradation from CT number errors in CBCT-based online-adaptive proton therapy.

IntroductionIn head-and-neck IMPT, trigger-based offline plan adaptation (Offlinetrigger-based) is often used. Our goal was to compare this to four alternative adaptive strategies for dosimetry, workload and treatment time, considering also foreseen further technological advancements, including anticipated automation. Materials and methodsAlternative strategies included weekly offline re-planning (Offlineweekly), daily plan selection from a library (Librarystatic and Libraryprogsressive) and a fast, approximate daily online re-optimization approach (Onlinere-opt). Impact on CTV coverage and NTCPs was assessed by simulations based on repeat-CTs from 15 patients. Full daily re-planning was used as dosimetric benchmark. Increases in workload and treatment time were estimated. ResultsBoth for coverage and NTCPs, fast Onlinere-opt performed as well as full re-planning. Compared to current practice, Onlinere-opt showed enhanced probabilities for high coverage, and resulted in reductions in grade ≥ II NTCPs of 4.6 ± 1.7 %-point for xerostomia and 4.2 ± 2.3 %-point for dysphagia. Offlineweekly and library strategies did not show coverage enhancements and resulted in smaller NTCP improvements. Further automation can largely limit workload and treatment time increases. With anticipated further automation, adaptation-related workload of Offlineweekly, Librarystatic, Libraryprogressive, and Onlinere-opt was expected to increase by 3, 8, 21, and 66 h for 35 fraction treatment courses compared to Offlinetrigger-based. The corresponding adaptation-related prolonged treatment times were estimated to be 0, 4, 6, and 29 min/fraction. ConclusionOnline adaptive strategies could approach dosimetric quality of full re-planning at the cost of additional workload and prolonged treatment time compared to the current offline adaptive strategy. Automation needs to play a key role in making more complex adaptive approaches feasible.

PurposeMany studies have demonstrated superior performance of Monte Carlo (MC) over type B algorithms in heterogeneous structures. However, even in homogeneous media, MC dose simulations should outperform type B algorithms in situations of electronic disequilibrium, such as small and highly modulated fields.Our study compares MC and Collapsed Cone (CC) dose algorithms in RayStation 12A. Under consideration are 6 MV and 6 MV flattening filter‐free (FFF) photon beams, relevant for VMAT plans such as head‐and‐neck and stereotactic lung treatments with heterogeneities, as well as plans for multiple brain metastases in one isocenter, involving highly modulated small fields. We aim to investigate collimator angle dependence of small fields and performance differences between different combinations of ArcCHECK configuration and dose algorithm.MethodsSeveral verification tests were performed, ranging from simple rectangular fields to highly modulated clinical plans. To evaluate and compare the performance of the models, the agreements between calculation and measurement are compared between MC and CC. Measurements include water tank measurements for test fields, ArcCHECK measurements for test fields and VMAT plans, and film dosimetry for small fields.Results and conclusionsIn very small or narrow fields, our measurements reveal a strong dependency of dose output to collimator angle for VersaHD with Agility MLC, reproduced by both dose algorithms.ArcCHECK results highlight a suboptimal agreement between measurements and MC calculations for simple rectangular fields when using inhomogeneous ArcCHECK images. Therefore, we advocate for the use of homogeneous phantom images, particularly for static fields, in ArcCHECK verification with MC.MC might offer performance benefits for more modulated treatment fields. In ArcCHECK results for clinical plans, MC performed comparable to CC for 6 MV. For 6 MV FFF and the preferred homogeneous phantom image, MC resulted in consistently better results (13%–64% lower mean gamma index) compared to CC.

The aim of this study is to develop and optimize an adiabatic ( ) mapping method for robust quantification of spin-lock (SL) relaxation in the myocardium at 3T. Adiabatic SL (aSL) preparations were optimized for resilience against and inhomogeneities using Bloch simulations. Optimized -aSL, Bal-aSL and -aSL modules, each compensating for different inhomogeneities, were first validated in phantom and human calf. Myocardial mapping was performed using a single breath-hold cardiac-triggered bSSFP-based sequence. Then, optimized preparations were compared to each other and to conventional SL-prepared maps (RefSL) in phantoms to assess repeatability, and in 13 healthy subjects to investigate image quality, precision, reproducibility and intersubject variability. Finally, aSL and RefSL sequences were tested on six patients with known or suspected cardiovascular disease and compared with LGE, , and ECV mapping. The highest preparation efficiency was obtained in simulations for modules comprising 2 HS pulses of 30 ms each. In vivo maps yielded significantly higher quality than RefSL maps. Average myocardial values were 183.28 25.53 ms, compared with 38.21 14.37 ms RefSL-prepared . maps showed a significant improvement in precision (avg. 14.47 3.71% aSL, 37.61 19.42% RefSL, p < 0.01) and reproducibility (avg. 4.64 2.18% aSL, 47.39 12.06% RefSL, p < 0.0001), with decreased inter-subject variability (avg. 8.76 3.65% aSL, 51.90 15.27% RefSL, p < 0.0001). Among aSL preparations, -aSL achieved the better inter-subject variability. In patients, -aSL preparations showed the best artifact resilience among the adiabatic preparations. times show focal alteration colocalized with areas of hyper-enhancement in the LGE images. Adiabatic preparations enable robust in vivo quantification of myocardial SL relaxation times at 3T.

Patients with locally advanced cervical cancer (LACC) treated with chemoradiation often experience hematologic toxicity (HT), as chemoradiation can induce bone marrow (BM) suppression. Studies on the relationship between BM dosimetric parameters and clinically significant HT might provide relevant indices for developing BM sparing (BMS) radiotherapy techniques. This systematic review studied the relationship between BM dose and HT in patients with LACC treated with primary cisplatin-based chemoradiation. A systematic search was conducted in Embase, Medline, and Web of Science. Eligibility criteria were treatment of LACC-patients with cisplatin-based chemoradiation and report of HT or complete blood cell count (CBC). The search identified 1346 papers, which were screened on title and abstract before two reviewers independently evaluated the full-text. 17 articles were included and scored according to a selection of the TRIPOD criteria. The mean TRIPOD score was 12.1 out of 29. Fourteen studies defining BM as the whole pelvic bone contour (PB) detected significant associations with V10 (3/14), V20 (6/14), and V40 (4/11). Recommended cut-off values were V10 > 95–75%, V20 > 80–65%, and V40 > 37–28%. The studies using lower density marrow spaces (PBM) or active bone marrow (ABM) as a proxy for BM only found limited associations with HT. Our study was the first literature review providing an overview of articles evaluating the correlation between BM and HT for patients with LACC undergoing cisplatin-based chemoradiation. There is a scarcity of studies independently validating developed prediction models between BM dose and HT. Future studies may use PB contouring to develop normal tissue complication probability models.

Early 1996 a three year (1996 - 1998) joint European project was launched under the name {open_quote}Advanced DIR-MCFC Development{close_quote}, aiming at the development of Direct Internal Reforming (DIR) Molten Carbonate Fuel Cell (MCFC) systems for cogeneration applications for the European market. In this project participate: Brandstofcel Nederland BV (BCN), British Gas pic (BG), Gaz de France (GDF), Netherlands Energy Research foundation (ECN), Stork, Royal Schelde and Sydkraft AB. The European Fuel Cell User Group (EFCUG) supports the project as an advisory board. Whereas the US and Japanese programmes are aimed at large-scale demonstrations of the MCFC technology, this project focusses on the development of concepts and technology, required for MCFC systems that will be competative on the cogeneration market. The project partners provide the essential expertise: from end-user, system engineering, stack development up to fundamental material research.