Frameless linac-based (Novalis TX) stereotactic treatment for vestibular schwannoma that extend distally into the iac (Internal Acoustic Canal): an analysis of the dose to the cochlea

Objectives: We compare the dose parameters between 3 different radiosurgery delivery techniques which may have an impact on cochlea function. Methods: Five patients with unilateral vestibular schwannoma (VS) were selected for this study. Planning procedure was carried out using the BrainLAB® iPlan planning system v. 4.5. For each patient three different planning techniques were used: dynamic arc (DA) with 5 arcs per plan, hybrid arc (HA) with 5 arcs per plan and IMRT with 8 fields per plan. For each technique, two plans were generated with different methods: with the first method (PTV coverage) it was the goal to fully cover the PTV with at least 12 Gy (normalization: 12 Gy covered 99% of the PTV) and with the second method (cochlea sparing) it was the goal to spare the cochlea (normalization: 12 Gy covers 50% of the PTV/V4Gy of cochlea lower than 1%). Plan evaluation was done considering target volume and coverage (conformity and homogeneity) and OAR constraints (mean (Dmean) and maximum dose (Dmax) to cochlea, Dmax to brainstem and cochlea). The total number of monitor units (MU) was analyzed. Results: The median tumor volume was 0.95 cm³ (range, 0.86-3 cm³). The median PTV was 1.44 cm³ (range, 1-3.5 cm³). The median distance between the tumor and the cochlea's modiulus was 2.7 mm (range, 1.8-6.3 mm). For the PTV coverage method, when we compared the cochlear dose in VS patients planned with DA, HA and IMRT, there were no significant differences in Dmax (p = 0.872) and in Dmean (p= 0.860). We found a significant correlation (p< 0.05) between the target volume and the cochlear Dmean for all plans with Pearson's coefficient correlation of 0.90, 0.92 and 0.94 for the DA, HA and IMRT techniques, respectively. For the cochlea sparing method, when we compared the cochlear dose in VS patients planned with DA, HA and IMRT, there were no significant differences in Dmax (p = 0.310) and in Dmean (p= 0.275). However, in this group the V4Gy of the ipsilateral cochlea represents less than 1%. When using the HA or IMRT technique, the homogeneity and conformity in the PTV, but also the number of MUs were increased in comparison to the DA technique. Conclusion: VS tumors that extend distally into the IAC had an equivalent sparing of cochlea with DA approach compared with the HA and IMRT techniques. Disclosure: No significant relationships.

Capability of a space-based space surveillance system to detect and track objects in GEO, MEO and LEO orbits

In this paper we present the results from the coverage and the orbit determination accuracy simulations performed within the recently completed ESA study “Assessment Study for Space Based Space Surveillance (SBSS) Demonstration System” (Airbus Defence and Space consortium). This study consisted in investigating the capability of a space based optical sensor (SBSS) orbiting in low Earth orbit (LEO) to detect and track objects in GEO (geosynchronous orbit), MEO (medium Earth orbit) and LEO and to determinate and improve initial orbits from such observations. Space based systems may achieve better observation conditions than ground based sensors in terms of astrometric accuracy, detection coverage, and timeliness. The primary observation mode of the proposed SBSS demonstrator is GEO surveillance, i.e. the systematic search and detection of unknown and known objects. GEO orbits are specific and unique orbits from dynamical point of view. A space-based sensor may scan the whole GEO ring within one sidereal day if the orbit and pointing directions are chosen properly. For an efficient survey, our goal was to develop a leak-proof GEO fence strategy. Collaterally, we show that also MEO, LEO and other (GTO,Molniya, etc.) objects would be possible to observe by the system and for a considerable number of LEO objects to down to size of 1 cm we can obtain meaningful statistical data for improvement and validation of space debris environment models

Bicyclo[3.2.1]amide-DNA: a chiral, non-chiroselective base-pairing system

The design, synthesis and base-pairing properties of bicyclo[3.2.1]amide-(bca)DNA, a novel phosphodiester based DNA analogue, is reported. This analogue consists of a conformationally constrained backbone entity which emulates a B-DNA geometry, to which the nucleobases were attached via an extended, acyclic amide linker. Homobasic adenine-containing bca-decamers form duplexes with complementary oligonucleotides containing the bca-, the DNA the RNA and, surprisingly, also the L-RNA backbone. UV- and CD-spectroscopic investigations revealed the duplexes with D- or L-complement to be of similar stability and enantiomorphic in structure. Bca-oligonucleotides containing all four bases form strictly antiparallel, left-handed complementary duplexes with itself and complementary DNA but not with RNA. Base-mismatch discrimination is comparable to that of DNA while the overall thermal stabilities of bca-oligonucleotide duplexes are inferior relative to that of DNA or RNA. A detailed molecular modeling study of left- and right-handed bca-DNA containing duplexes showed only minor changes in the backbone structure and revealed a structural switch around the base-linker unit to be responsible for the generation of enantiomorphic duplex structures. The obtained data are discussed with respect to the structural and energetic role of the ribofuranose entities in DNA and RNA association

GROMOS-C, a novel ground-based microwave radiometer for ozone measurement campaigns

Stratospheric ozone is of major interest as it absorbs most harmful UV radiation from the sun, allowing life on Earth. Ground-based microwave remote sensing is the only method that allows for the measurement of ozone profiles up to the mesopause, over 24 hours and under different weather conditions with high time resolution. In this paper a novel ground-based microwave radiometer is presented. It is called GROMOS-C (GRound based Ozone MOnitoring System for Campaigns), and it has been designed to measure the vertical profile of ozone distribution in the middle atmosphere by observing ozone emission spectra at a frequency of 110.836 GHz. The instrument is designed in a compact way which makes it transportable and suitable for outdoor use in campaigns, an advantageous feature that is lacking in present day ozone radiometers. It is operated through remote control. GROMOS-C is a total power radiometer which uses a pre-amplified heterodyne receiver, and a digital fast Fourier transform spectrometer for the spectral analysis. Among its main new features, the incorporation of different calibration loads stands out; this includes a noise diode and a new type of blackbody target specifically designed for this instrument, based on Peltier elements. The calibration scheme does not depend on the use of liquid nitrogen; therefore GROMOS-C can be operated at remote places with no maintenance requirements. In addition, the instrument can be switched in frequency to observe the CO line at 115 GHz. A description of the main characteristics of GROMOS-C is included in this paper, as well as the results of a first campaign at the High Altitude Research Station at Jungfraujoch (HFSJ), Switzerland. The validation is performed by comparison of the retrieved profiles against equivalent profiles from MLS (Microwave Limb Sounding) satellite data, ECMWF (European Centre for Medium-Range Weather Forecast) model data, as well as our nearby NDACC (Network for the Detection of Atmospheric Composition Change) ozone radiometer measuring at Bern.

Comparison of co-located independent ground-based middle atmospheric wind and temperature measurements with numerical weather prediction models

High-resolution, ground-based and independent observations including co-located wind radiometer, lidar stations, and infrasound instruments are used to evaluate the accuracy of general circulation models and data-constrained assimilation systems in the middle atmosphere at northern hemisphere midlatitudes. Systematic comparisons between observations, the European Centre for Medium-Range Weather Forecasts (ECMWF) operational analyses including the recent Integrated Forecast System cycles 38r1 and 38r2, the NASA’s Modern-Era Retrospective Analysis for Research and Applications (MERRA) reanalyses, and the free-running climate Max Planck Institute–Earth System Model–Low Resolution (MPI-ESM-LR) are carried out in both temporal and spectral dom ains. We find that ECMWF and MERRA are broadly consistent with lidar and wind radiometer measurements up to ~40 km. For both temperature and horizontal wind components, deviations increase with altitude as the assimilated observations become sparser. Between 40 and 60 km altitude, the standard deviation of the mean difference exceeds 5 K for the temperature and 20 m/s for the zonal wind. The largest deviations are observed in winter when the variability from large-scale planetary waves dominates. Between lidar data and MPI-ESM-LR, there is an overall agreement in spectral amplitude down to 15–20 days. At shorter time scales, the variability is lacking in the model by ~10 dB. Infrasound observations indicate a general good agreement with ECWMF wind and temperature products. As such, this study demonstrates the potential of the infrastructure of the Atmospheric Dynamics Research Infrastructure in Europe project that integrates various measurements and provides a quantitative understanding of stratosphere-troposphere dynamical coupling for numerical weather prediction applications.

Assessment of the Hong Kong Liver Cancer Staging System in Europe.

BACKGROUND & AIMS European and American guidelines have endorsed the Barcelona Clinic Liver Cancer (BCLC) staging system. The aim of this study was to assess the performance of the recently developed Hong Kong Liver Cancer (HKLC) classification as a staging system for hepatocellular carcinoma (HCC) in Europe. METHODS We used a pooled set of 1693 HCC patients combining three prospective European cohorts. Discrimination ability between the nine substages and five stages of the HKLC classification system was assessed. To evaluate the predictive power of the HKLC and BCLC staging systems on overall survival, Nagelkerke pseudo R2, Bayesian Information Criterion and Harrell's concordance index were calculated. The number of patients who would benefit from a curative therapy was assessed for both staging system. RESULTS The HKLC classification in nine substages shows suboptimal discrimination between the staging groups. The classification in five stages shows better discrimination between groups. However, the BCLC classification performs better than the HKLC classification in the ability to predict OS. The HKLC treatment algorithm tags significantly more patients to curative therapy than the BCLC. CONCLUSIONS The BCLC staging system performs better for European patients than the HKLC staging system in predicting OS. Twice more patients are eligible for a curative therapy with the HKLC algorithm, whether this translates in survival benefit remains to be investigated. This article is protected by copyright. All rights reserved.