Siegfried Kollotzek

Background and purpose: Hybrid DCAT/VMAT techniques, introduced in a new version of the treatment planning software Elements 4.0, allow variable dose rate modulation, adding flexibility to plan optimization. However, the delivery capability of linear accelerators under these conditions has not been systematically assessed. We report on delivery irregularities observed with an Elekta Versa HDlinac, investigated using the IQM detector. Materials and methods: Patient plans with visible irregular gantry motion and corresponding IQMfluctuations were selected for analysis. Linac service mode data (338 parameters) were recorded during delivery, with a focus on gantry angle, gantry speed, delivered MU, dose rate, leaf motion, and error signals. The plans were subsequently redelivered at a reduced maximum dose rate (600 MU/min vs. 200 MU/min) to evaluate the impact on delivery stability. Results: At 600 MU/min, the linac frequently reached its technical limits, resulting in irregular gantry speed, fast leaf motion, and over-undershoot patterns in IQM measurements. With a reduced maximum dose rate of 200 MU/min, dose delivery was stabilized: gantry and leaf trajectories were smooth, dose-rate saturation was avoided, and IQMsignalsshowedconsistentagreementwithplanned values. Conclusion: Hybrid DCAT/VMAT plans with variable dose rates may approach the technical limits of the linac when delivered at the maximum dose rate, while still remaining within clinical tolerances. Independent QA using the IQM detector is effective in identifying these limitations. Reducing the maximum dose rate restores stable delivery. Future studies involving additional plans and linacs, including validation with a second IQM system, are planned to confirm these findings and support clinical recommendations.

Background: Distinguishing vital from non-vital persistent cervical lymph nodes after chemoradiotherapy in HNSCC remains clinically challenging. We investigated whether image-level data augmentation improves CT-based radiomics classification for this task. Methods: We evaluated eight augmentation strategies and their 28 pairwise combinations in 55 patients, using Bayesian hyperparameter tuning with Optuna for parameter optimization. A radiomics pipeline comprising Radiomics features, five feature selectors, and seven classifiers was assessed using patient-level stratified 5-fold cross-validation. Configurations were ranked using a composite score defined as the mean of AUC, ACC and F1-score. Results: Feature selection improved the composite score from 0.659 to 0.742. The best augmented configuration, Window Contrast Variation, achieved a composite score of 0.803 and an AUC of 0.831, corresponding to an 8.2% relative point-estimate gain over feature selection alone and a 21.9% gain over the no-selection baseline when feature selection and augmentation were combined. Conclusions: These findings suggest that feature selection with optimized augmentation may enhance radiomics-based lymph node classification. However, individual augmentation-versus-baseline differences did not reach statistical significance in this limited sample, requiring confirmation in larger cohorts.

The evaporative decay of mixed heavy and light water clusters was measured. The branching ratios of the three isotopologue molecules scale with the deuterium fraction from cluster size N=9 and up, including across the well-known shell closing at N=21, and are consistent with macroscopic surface values. Differences in the free energies of competing channels derived from the scaled distributions take the simplest possible form of a single energy parameter and the deuterium-protium mixing entropy. The observations here represent a direct observation of the isotopic mixing entropy. The energy parameter is consistent with zero point vibrational energy differences of the free and condensed water molecule for both H_{2}O/HDO and HDO/D_{2}O ratios.

Background/Objectives: Informed consent is crucial in medical practice, especially for complex treatments such as postoperative radiotherapy for patients with breast cancer. Conventional consent procedures are often based on verbal declarations with a highly condensed but nevertheless large amount of information, which can exceed the recording capacity of patients and lead to misunderstandings. The aim of this study was to develop and test an educational video on breast cancer patients to enhance the informed consent process by improving patients’ understanding and reducing the duration of the subsequent consultation. Methods: The educational video was created after the underlying content was determined by a modified Delphi method in which a panellist of radiation oncologists, nurses, radiation therapists, and former patients participated in successive rounds of topic scoring. After achieving content consent, the video included 19 items to cover key aspects of postoperative radiotherapy in a patient-friendly manner. Fifty breast cancer patients scheduled for postoperative radiotherapy were randomised to watch the video prior to their verbal consultation (n = 25) or to the control group participating in the traditional informed consent process only (n = 25). The duration of the informed consent processes in both arms was recorded. To assess the educational effect of the video, a multiple-choice test was created. In addition, patients’ satisfaction was recorded using a separate questionnaire. Both questionnaires were completed by the patients one to two hours after signing the consent form. Results: The patients in the video group evidenced significantly higher knowledge scores than those who received standard verbal explanations (median number of correct answers 9 vs. 8 out of 10, p = 0.0039). The whole informed consent process was also completed faster in the video group (mean duration 34.7 vs. 46.2 min, p < 0.001). Median satisfaction scores were high in both groups (34 vs. 33 out of 35 points), with no significant differences observed (p > 0.05). Conclusion: The educational video effectively improved patient understanding and streamlined the informed consent process without compromising patients’ satisfaction. This approach also helps to standardise the delivery of complex medical information, and it can also be adapted to improve the informed consent process for other cancer treatments.

We underscore a solid agreement between experimental and computational studies on solvation of pristine/protonated Cu_n⁺ (n = 1–2) in H₂. For instance, with n = 1, the initial shell comprises four covalently bound H₂; subsequent ones are non-covalent.

Correction for ‘Helium nanodroplets as an efficient tool to investigate hydrogen attachment to alkali cations’ by Siegfried Kollotzek et al. , Phys. Chem. Chem. Phys. , 2023, 25 , 462–470, https://doi.org/10.1039/D2CP03841B.

The most stable structure of cationic (left) and anionic (right) Cu₅ was determined by particularly stable configurations with He.

We report a novel method to reversibly attach and detach hydrogen molecules to positively charged sodium clusters formed inside a helium nanodroplet host matrix. It is based on the controlled production of multiply charged helium droplets which, after picking up sodium atoms and exposure to H₂ vapor, lead to the formation of Na_m ⁺(H₂)_n clusters, whose population was accurately measured using a time-of-flight mass spectrometer. The mass spectra reveal particularly favorable Na⁺(H₂)_n and Na₂ ⁺(H₂)_n clusters for specific “magic” numbers of attached hydrogen molecules. The energies and structures of these clusters have been investigated by means of quantum-mechanical calculations employing analytical interaction potentials based on ab initio electronic structure calculations. A good agreement is found between the experimental and the theoretical magic numbers.