[en] The planned permanent underground repository for non-heat-generating wastes in the former Konrad iron-ore mine is now in the final stages of the plan approval procedures. The deadline for the final stages of the plan approval procedures for the Gorleben salt dome is approaching. It is time to give an account of what has been accomplished in the geotechnical field. The BGR has developed a complex geotechnical stability analysis that takes into account the requirements of permanent storage and the objectives required for the protection of the biosphere. This stability analysis is based on the following considerations: Owing to the complexity of the boundary conditions, a cavity intended for a permanent repository can be demonstrated to be safe only by a combination of studies and simulations. These studies must integrate engineering geology, geotechnics, rock mechanics, statics, monitoring of the conditions in the repository, and mining expertise. (orig.) With 27 figs

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[en] This thesis presents a study of the exclusive decays B^± → η_cK^± and B⁰ → η_cK_S⁰ with η_c → K_S⁰K^±π^±, η_c → K⁺K^-π⁰ and η_c → K⁺K^-K⁺K^-, and the measurement of their branching ratios. We use 20.7 fb^-1 of data collected by the experiment BABAR at the γ(4S) resonance between October 1999 and October 2000. These data correspond to 23 million BB-bar pairs. In the decays η_c → K_S⁰K^±π^± and η_c → K⁺K^-π⁰ the observed signals are statistically significant; they allow to measure the branching ratios. Upper limits are set, in the channels with η_c → K⁺K^-K⁺K^-: B(B⁺→η_cK⁺) * B(η_c→K⁺K^-K⁺K^-) < 5,6 x 10^-6 (90% confidence level); B(B⁺→η_cK⁺) * B(η_c→K⁰K^-π⁺+c.c.) (52,8±7,9±7,3) x 10^-6; B(B⁺→η_cK⁺) * B(η_c→K⁺K^-π⁰) (15,5±3,6±2,5) x 10^-6; B(B⁰→η_cK⁰) * B(η_c→ K⁺K^-K⁺K^-) < 2,3 x 10^-6 (90% confidence level); B(B⁰→η_cK⁰) * B(η_c→K⁰K^-π⁺+c.c.) (36,8±11,6±6,0)x 10^-6; B(B⁰→η_cK⁰) * B(η_c→ K⁺K^-π⁰) = (11,3±5,1±2,4) x 10^-6; where the first error is statistical and the second systematic. The average of the branching ratio of η_c →K_S⁰K^±π^± and η_c → K⁺K^-π⁰ for the channels B^± → η_cK^± and B⁰ → η_cK_S⁰, taking into account the common systematical errors, leads to: B(B⁺→η_cK⁺) * B(η_c→KK-barπ) = (82,5±10,4±8,3) x 10^-6 and B(B⁰→η_cK⁰) * B(η_c→ KK-barπ) (58,1±15,2±6,3) x 10^-6. The ratios R_K ≡ Γ(B →η_cK)/Γ(B →J/ψK) have been determined to R_K(B⁺) 1,48 ± 0,19 ± 0,17 ± 0,46 and R_K(B⁰) = 1,24 ± 0,33 ± 0,16 ± 0,38. These measurements are dominated by the uncertainty on the world average of the η_c → KK-barπ branching ratio (third error). Our results are compatible with the theoretical predictions, which cover a large range; it is not possible to obtain stronger conclusions. (author)

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[en] Purpose: The treatment of post operative head and neck cancers traditionally involves the use of opposed lateral fields in conjunction with low neck field(s) to a dose of 40 - 45 Gy. This technique involves a critical field match involving both the primary disease site and the cervical spinal cord. A gap leads to an under dose in the target tissue, while an overlap could damage the spinal cord. An alternative technique, using a 'mini-mantle' opposed AP-PA pair, avoids the field matching problem, but is limited by the large target volume dose inhomogeneity and cord dose constraints. An ideal treatment would allow both a sufficient (45 - 50 Gy) dose and an acceptable target volume dose inhomogeneity. The purpose of this investigation was to develop an alternative treatment technique using optimized field-in-field intensity modulation with constrained simulated annealing and provide a dosimetric comparison of this technique with the conventional and mini-mantle techniques. Method: The optimized field-in-field intensity modulated technique was defined as a single PA field with 12 AP fields, each with a common inferior border and common isocenter. Successive fields are 2 cm longer than the proceeding fields. Each field is shaped to conform to the projection of the target volume and its beam weight is defined at the field center. An additional field, 4 cm in length, overlaps the superior region of the target volume to provide a superior boost. A cost function, minimum target volume dose (MTV), was selected. The weights of each field were determined by maximizing the MTV subject to the selected dose-volume constraints. Optimization was accomplished using a variant of our clinical constrained simulated annealing algorithm, modified to reject solutions which exceed the allowed target volume inhomogeneity (TVI). Results: The table gives the minimum and maximum target volume dose and TVI defined as TVI ((TVDose_max - TVDose_min)(TVDose_min)) for each of the three techniques for a typical case. In each technique, the minimum target volume dose was increased until the normal tissue dose-volume constraints were met. Cord dose was restricted to 45 Gy, 75% of the treatment volume was restricted to 48 Gy or less, and the maximum TVI was 20%. The new technique was able to meet the prescribed constraints and allowed a moderate increase in the minimum target volume dose. Addition of high energy (15 MV) x-rays to the posterior field improved the resulting dose distribution in some cases. Conclusions: 1) Optimized field-in-field intensity modulation produces acceptable dose distributions for post-op head and neck treatments. Conventional dose-volume constraints can be met and superior TVI constraints can be satisfied. This allows a modest escalation of the dose for first course post-op head and neck disease. 2) Constrained simulated annealing is a simple and useful technique to optimize beam weights for few-beam intensity modulation

[en] Side effects of the contrast medium iohexol (300 mgI/ml) were evaluated in an open clinical multicenter study that included 2,118 patients. In one third of the examinations head and neck vessels were studied, in two thirds of examinations thoracic, abdominal, or femoral arteries were studied. Some 87% of the patients had no pain sensation, whereas only 64% did not have a heat feeling. The heat feeling was tolerable in 27% and untolerable in 9%. Cardiovascular disturbances such as a decrease in blood pressure or bradycardia were seen in 1.9%, cerebral manifestations such as transient ischemia in 1.5%. Allergy-like symptoms with a cutaneous manifestation or bronchospasm were seen in only 0.4% of all studies. Patients with a known history of allergic diathesis had three times the number of moderate side effects than patients with no history of allergy

[en] Purpose: Simulated annealing (SA) allows for the implementation of realistic biological and clinical cost functions into treatment plan optimization. However, a drawback to the clinical implementation of SA optimization is that large numbers of beams appear in the final solution, some with insignificant weights, preventing the delivery of these optimized plans using conventional (limited to a few coplanar beams) radiation therapy. A preliminary study suggested two promising algorithms for restricting the number of beam weights. The purpose of this investigation was to compare these two algorithms using our current SA algorithm with the aim of producing a algorithm to allow clinically useful radiation therapy treatment planning optimization. Method: Our current SA algorithm, Variable Stepsize Generalized Simulated Annealing (VSGSA) was modified with two algorithms to restrict the number of beam weights in the final solution. The first algorithm selected combinations of a fixed number of beams from the complete solution space at each iterative step of the optimization process. The second reduced the allowed number of beams by a factor of two at periodic steps during the optimization process until only the specified number of beams remained. Results of optimization of beam weights and angles using these algorithms were compared using a standard cadre of abdominal cases. The solution space was defined as a set of 36 custom-shaped open and wedged-filtered fields at 10 deg. increments with a target constant target volume margin of 1.2 cm. For each case a clinically-accepted cost function, minimum tumor dose was maximized subject to a set of normal tissue binary dose-volume constraints. For this study, the optimized plan was restricted to four (4) fields suitable for delivery with conventional therapy equipment. Results: The table gives the mean value of the minimum target dose obtained for each algorithm averaged over 5 different runs and the comparable manual treatment plan value. The inter-run variation for the combination algorithm was less than 2 Gy compared to 3.8 Gy for the reduction algorithm. In 5 of 6 cases the combination algorithm gave higher minimum target volume doses. Optimization times averaged 9 minutes compared to over 40 minutes for a manually-produced treatment plan with a reduced cost function. It is interesting to note that SA optimization restricted to 4 beams gives results comparable to earlier optimization work using 36 open field beams. Whether this is due to the np-complexity of the 36 beam solution space or to the optimal nature of the 4 beam solution requires further research. Conclusion: 1) Either algorithm allows for a significant dose escalation compared to manual treatment plans. 2) The beam combination algorithm generally produced higher target volume doses with less variation among optimization runs. 3) Optimization runs take less than 10 minutes using current CPUs compared to 40 minutes for a manual treatment plan. 4) SA optimization runs using 4 beams with wedges give results comparable to previous optimization runs using 36 open-field beams

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[en] Since Januray 1983, the authors have been performing all gastrointestinal examinations in premature infants, newborns, and small infants with use of nonionic water-soluble contrast agents. They have been using iohexol in a 1:1 dilution, containing 150 mgJ/mL, which is nearly isoosmolal to blood, or iopamidol Gastro, containing 300 mgJ/mL. They report on our experience with 431 patients, 75% undergoing gastrointestinal studies at a dosage of 5 mL/kg body weight and 25% undergoing enemas at 5-10 mL/kg. The main advantages are the lack of fluid shift, the decreased toxicity to the lungs after aspiration, and the ready resorption after perforation. So far they have not observed any adverse effects. The resorption by the bowel mucosa is less than 1%

[en] The paper describes the work during the planning and construction of underground repositories for radioactive wastes in rock salt. In the safety assessment the geotechnical stability analysis is a critical part. Such an analysis comprises an engineering-geological study of the site, laboratory and in-situ experiments, geomechanical modelling, and numerical static calculations. Comments on new research data on the mechanical behaviour of rock salt are given. The Gorleben repository project is an example demonstrating how modern geotechnical research and investigation methods can help to secure the safe isolation of wastes from the biosphere