Commissioning, dosimetric characterization and machine performance assessment of the LIAC HWL mobile accelerator for Intraoperative Radiotherapy.

BACKGROUND: The LIAC HWL (Sordina IORT Technologies, Vicenza, Italy) is a recently designed mobile linear accelerator for intraoperative electron radiotherapy (IOeRT), producing high dose rate electron beams at four different energy levels. It features a software tool for the visualization of 2D dose distributions, which is based on Monte Carlo simulations. The aims of this work were to (i) assess the dosimetric characteristics of the accelerator, (ii) experimentally verify calculated data exported from the software and (iii) report on commissioning as well as performance of the system during the first year of operation. METHODS: The electron energies of the LIAC HWL used in this study are 6, 8, 10 and 12 MeV. Diameters of the cylindrically shaped applicators range from 3 to 10cm. We studied two applicator sets with different length ratios of proximal and terminal applicator sections. Reference dosimetry, linearity as well as short- and long-term stability were measured with a PTW Advanced Markus chamber, relative depth dose and profiles were measured using an unshielded diode. Percentage-depth-dose (PDD) and transversal dose profile (TDP) data were exported from the simulation software LIACSim and compared with our measurements. RESULTS: The device reaches dose rates up to 40Gy/min (for 12 MeV). Surface doses for the 10cm applicators are higher than 90%, X-ray background is below 0.6% for all energies. Simulations and measurements of PDD agreed well, with a maximum difference in the depth of the 50% isodose of 0.7mm for the flat-ended applicators and 1mm for the beveled applicators. The simulations slightly underestimate the dose in the lateral parts of the field (difference < 1.8% for flat-ended applicators). The two different applicator sets were dosimetrically equivalent. Long-term stability measurements for the first year of operation ranged from -2.1% to 1.6% (mean: -0.1%). CONCLUSIONS: The system is dosimetrically well suited for IOeRT and performed stably and reliably. The software tool for visualization of dose distributions can be used to support treatment planning, following thorough validation.

Laryngeal Tube Practice in a Metropolitan Ambulance Service: A Five-year Retrospective Observational Study (2009-2013).

Background: The endotracheal tube (ETT) is considered the gold standard in emergency airway management, although supraglottic airway devices, especially the laryngeal tube (LT), have recently gained in importance. Although regarded as an emergency device in case of failure of endotracheal intubation in most systems, we investigated the dynamics of the use of the LT in a metropolitan ambulance service without any regulations on the choice of airway device. Methods: A retrospective, observational study on all patients from the Municipal Ambulance Service, Vienna in need of advanced airway management over a 5-year period. Differences between years were compared; influencing factors for the use of the LT were analyzed using multivariable logistic regression. Results: In total 5,175 patients (mean age 62 ± 20 years, 36.6% female) underwent advanced airway management. Of these, 15.6% received the LT. LT use increased from 20 out of 1,001 (2.0%) in 2009 to 292 of 1,085 (26.9%) in 2013 (p < 0.001). The increase between each consecutive year was also significant. Paramedics more frequently inserted the LT than physicians (RR 1.80 (95%CI 1.48-2.16); p < 0.001). Female patients received a LT less frequently (RR 0.84 (95%CI 0.72-0.97), p = 0.013). There was no difference regarding airway device due to underlying causes requiring airway management and no relationship to the NACA-score. Conclusion: In a European EMS system of physician and paramedic response, the proportion of airway managed by LT over ETT rose considerably over five years. Although the ET is still the gold standard, the LT is gaining in importance for EMS physicians and paramedics.

Ultracold neutron detectors based on 10B converters used in the qBounce experiments.

Gravity experiments with very slow, so-called ultracold neutrons connect quantum mechanics with tests of Newton's inverse square law at short distances. These experiments face a low count rate and hence need highly optimized detector concepts. In the frame of this paper, we present low-background ultracold neutron counters and track detectors with micron resolution based on a 10B converter. We discuss the optimization of 10B converter layers, detector design and concepts for read-out electronics focusing on high-efficiency and low-background. We describe modifications of the counters that allow one to detect ultracold neutrons selectively on their spin-orientation. This is required for searches of hypothetical forces with spin-mass couplings. The mentioned experiments utilize a beam-monitoring concept which accounts for variations in the neutron flux that are typical for nuclear research facilities. The converter can also be used for detectors, which feature high efficiencies paired with high spatial resolution of [Formula: see text]. They allow one to resolve the quantum mechanical wave function of an ultracold neutron bound in the gravity potential above a neutron mirror.