[en] Purpose: To develop a novel method to monitor external anatomical changes in head and neck cancer patients in order to help guide adaptive radiotherapy decisions. Methods: The method, developed in MATLAB, reveals internal anatomical changes based on variations observed in external anatomy. Weekly kV-CBCT scans from 11 Head and neck patients were retrospectively analyzed. The pre-processing step first corrects each CBCT for artifacts and removes pixels from the immobilization mask to produce an accurate external contour of the patient’s skin. After registering the CBCTs to the initial planning CT, the external contours from each CBCT (CBCTn) are transferred to the first week — reference — CBCT_1. Contour radii, defined as the distances between an external contour and the central pixel of each CBCT slice, are calculated for each scan at angular increments of 1 degree. The changes in external anatomy are then quantified by the difference in radial distance between the external contours of CBCT1 and CBCTn. The radial difference is finally displayed on a 2D intensity map (angle vs radial distance difference) in order to highlight regions of interests with significant changes. Results: The 2D radial difference maps provided qualitative and quantitative information, such as the location and the magnitude of external contour divergences and the rate at which these deviations occur. With this method, anatomical changes due to tumor volume shrinkage and patient weight loss were clearly identified and could be correlated with the under-dosage of targets or over-dosage of OARs. Conclusion: This novel method provides an efficient tool to visualize 3D external anatomical modification on a single 2D map. It quickly pinpoints the location of differences in anatomy during the course of radiotherapy, which can help determine if a treatment plan needs to be adapted

[en] Purpose: Superficial soft x-ray applicators have recently been designed for use with existing intra-operative radiotherapy systems. These applicators may be used in treating superficial lesions which are conventionally treated with electron beams. The purpose of this abstract is to compare dose distributions of an intra-operative 50kV x-ray unit with low energy electrons for the treatment of superficial lesions. Methods: Dosimetric parameters for 1 and 3-cm diameter Intrabeam superficial x-ray applicators were measured with EBT3 Gafchromic film in a solid water phantom. Depth dose distributions and profiles (d=2, 5, 10 and 15mm) were obtained by prescribing a dose of 400cGy at 5mm depth below the phantom surface. Corresponding dose profiles for 6-MeV electrons were acquired from a Varian Clinac 21EX at 100 SSD. H and D calibration curves were generated for each modality for 0-800cGy. Results: Dose coverage, penumbra, dose uniformity, surface dose, and dose fall-off were examined. Compared to electrons, Intrabeam lateral dose coverage at 5mm depth was 70% larger with a much sharper (1/4) penumbra. Electron isodose levels bulged with depth, whereas Intrabeam isodose levels exhibited a convex cone shape. The Intrabeam dose profiles demonstrated horns in the dose distribution up to a 5mm depth and an exponential dose fall-off. Relative surface dose was higher for the Intrabeam applicators. Treatment times were comparable for both modalities. Conclusions: The very small penumbra of Intrabeam at shallow depths could be useful in treating superficial lesions adjacent to critical structures. The exponential dose fall-off of Intrabeam makes it appealing in the sparing of structures beyond the lesion. However, for lesions past a depth of 5mm, electrons would be desirable as they penetrate farther and provide skin sparing. Intrabeam may be preferable for sites that are difficult to treat with electrons due to mechanical and physical limitations

[en] A search for in-beam γ - ray transitions in ¹⁰¹Sn, which contains only one neutron outside the ¹⁰⁰Sn core, using a novel approach was carried out at the Argonne Tandem-Linac System. ¹⁰¹Sn nuclei were produced using the ⁴⁶Ti(⁵⁸Ni, 3n)¹⁰¹Sn fusion-evaporation reaction. Beta-delayed protons with energies and decay times consistent with previous ¹⁰¹Sn decay studies were observed at the focal plane of the Fragment Mass Analyzer. In beam γ rays were detected in the Gammasphere Ge-detector array and were correlated with the ¹⁰¹Sn β - delayed protons using the Recoil-Decay Tagging method. As a result, a γ - ray transition between the single-neutron νg_7/2 and νd_5/2 states situated at the Fermi surface was identified. The measured νg_7/2 - νd_5/2 energy splitting was compared with predictions corresponding to various mean-field potentials and was used to calculate multi-neutron configurations in light Sn isotopes. Similar approach can be used to study core excitations in ¹⁰¹Sn and other exotic nuclei near ¹⁰⁰Sn. (author)

No abstract available

[en] Purpose: Frameless Stereotactic radiosurgery (SRS) is increasingly used in the clinic. Cone-Beam CT (CBCT) to simulation-CT match has replaced the 3-dimensional coordinate based set up using a stereotactic localizing frame. The SRS frame however served as both a localizing and immobilizing device. We seek to measure the quality of frameless (mask based) and frame based immobilization and evaluate its impact on target dose. Methods: Each SRS patient was set up by kV on-board imaging (OBI) and then fine-tuned with CBCT. A second CBCT was done at treatment-end to ascertain intrafraction motion. We compared pre- vs post-treatment CBCT shifts for both frameless and frame based SRS patients. CBCT to sim-CT fusion was repeated for each patient off-line to assess systematic residual image registration error. Each patient was re-planned with measured shifts to assess effects on target dose. Results: We analyzed 11 patients (12 lesions) treated with frameless SRS and 6 patients (11 lesions) with a fixed frame system. Average intra-fraction iso-center positioning errors for frameless and frame-based treatments were 1.24 ± 0.57 mm and 0.28 ± 0.08 mm (mean ± s.d.) respectively. Residual error in CBCT registration was 0.24 mm. The frameless positioning uncertainties led to target dose errors in Dmin and D95 of 15.5 ± 18.4% and 6.6 ± 9.1% respectively. The corresponding errors in fixed frame SRS were much lower with Dmin and D95 reduced by 4.2 ± 6.5% and D95 2.5 ± 3.8% respectively. Conclusion: Frameless mask provides good immobilization with average patient motion of 1.2 mm during treatment. This exceeds MRI voxel dimensions (∼0.43mm) used for target delineation. Frame-based SRS provides superior patient immobilization with measureable movement no greater than the background noise of the CBCT registration. Small lesions requiring submm precision are better served with a frame based SRS.

[en] Purpose: Investigate the impact of tissue inhomogeneities on dose distributions produced by low-energy X-rays in intra-operative radiotherapy (IORT). Methods: A 50-kV INTRABEAM X-ray device with superficial (Flat and Surface) applicators was commissioned at our institution. For each applicator, percent depth-dose (PDD), dose-profiles (DP) and output factors (OF) were obtained. Calibrated GaFchromic (EBT3) films were used to measure dose distributions in solid water phantom at various depths (2, 5, 10, and 15 mm). All recommended precautions for film-handling, film-exposure and scanning were observed. The effects of tissue inhomogeneities on dose distributions were examined by placing air-cavities and bone and tissue equivalent materials of different density (ρ), atomic number (Z), and thickness (t = 0–4mm) between applicator and film detector. All inhomogeneities were modeled as a cylindrical cavity (diameter 25 mm). Treatment times were calculated to deliver 1Gy dose at 5mm depth. Film results were verified by repeat measurements with a thin-window parallel plate ion-chamber (PTW 34013A) in a water tank. Results: For a Flat-4cm applicator, the measured dose rate at 5mm depth in solid water was 0.35 Gy/min. Introduction of a cylindrical air-cavity resulted in an increased dose past the inhomogeneity. Compared to tissue equivalent medium, dose enhancement due to 1mm, 2mm, 3mm and 4mm air cavities was 10%, 16%, 24%, and 35% respectively. X-ray attenuation by 2mm thick cortical bone resulted in a significantly large (58%) dose decrease. Conclusion: IORT dose calculations assume homogeneous tissue equivalent medium. However, soft X-rays are easily affected by non-tissue equivalent materials. The results of this study may be used to estimate and correct IORT dose delivered in the presence of tissue inhomogeneities

[en] The ecological monitoring study of the fishing resources at the Flamanville site (Manche, France) aims at evaluating the natural variations of the main hydro-biological parameters and at analysing the potential impact of the Flamanville nuclear power plant on the marine environment and its resources. This report presents the information gained on crustaceans biology for the year 1984 on the basis of industrial and experimental fishing data, and on lobsters tagging

[en] The assessment of the quality of a permanent implant of grains for a prostate cancer treatment is based on the dosimetric plan performed before the grain implantation or shortly after. The authors report a study of the correlation between 'under-dosed' areas assessed at the time of relapse, and intra-prostatic relapse sites. The study is based on 24 cases of proved intra-prostatic relapse. The prostatic volume has been divided into 12 areas, and three types of under-dosing have been defined. Parameters are the dose received by 90 per cent of the volume, and the volume receiving 100 per cent of the dose. A correlation appears between positive biopsies and 'under-dosing'. This corresponds to a bad quality implantation of grains for patients in a situation of prostatic relapse after implantation. Short communication

[en] Due to recent advances in detection techniques, excited states in several trans-fermium nuclei were studied in many laboratories worldwide, shedding light on the evolution of nuclear structure between stable nuclei and the predicted island of stability centered around spherical magic numbers. In particular, studies of K-isomers around the Z=100 and N=152 deformed shell closures extended information on the energies of Nilsson orbitals at the Fermi surface. Some of these orbitals originate from spherical states, which are relevant to the magic gaps in super-heavy nuclei. The single-particle energies can be used to test various theoretical predictions and aid in extrapolations towards heavier systems. So far, the Woods-Saxon potential reproduces the data best, while self-consistent approaches miss some of the observed features, indicating a need to modify the underlying effective nucleon-nucleon interactions.

[en] Airborne Wind Energy (AWE) is a promising new technology, and attracts a growing academic and industrial attention. Important research efforts have been deployed to develop prototypes in order to test the technology, generate control algorithms and optimize the efficiency of AWE systems. By today, a large set of control and optimization methods is available for AWE systems. However, because no validated reference model is available, there is a lack of benchmark for these methods. In this paper, we provide a reference model for pumping mode AWE systems based on rigid wings. The model describes the flight dynamics of a tethered 6 degrees of freedom (DOF) rigid body aircraft in form of differential-algebraic equations, based on Lagrange dynamics. With the help of least squares fitting the model is assessed using real flight data from the Ampyx Power prototype AP2. The model equations are smooth and have a low symbolic complexity, so as to make the model ideal for optimization and control. The information given in this paper aims at providing AWE researchers with a model that has been validated against flight data and that is well suited for trajectory and power output simulation and optimization.