61 research outputs found
Variants for a Riesenrad Ion Gantry
Hadrontherapy is widely believed to improve cancer treatment. The Bragg-peak effect of hadrons (protons and ions) makes them suitable for high precision and conformal scanning of tumours. To maximise the benefit it should be possible to deliver the particle beam from any direction in space towards the patient. A machine capable of performing such a task is called a medical gantry. So far only proton gantries have been built. The increased (magnetic) beam rigidity of say carbon ions yields considerable structural difficulties and has so far prevented realisation of an ion gantry. The structure would have to support large and very heavy bending magnets (50 t and more) and nevertheless deliver the beam with a sub-millimetre precision onto a patient in a supine position. The promising concept of a Riesenrad Gantry is suited to overcome this deadlock. The basic idea is to deflect the ion beam with a single 90° dipole, which rotates around the incoming beam axis, and direct it towards the eccentrically positioned patient cabin. Inside the (rotating) cabin similar conditions as in a classical isocentric treatment room prevail. The objective of this paper is to present and - to a certain degree - evaluate different versions of a Riesenrad gantry with clear focus on the mechanical performance. Two different ideas of how to achieve the specified accuracy are presented. Emphasis is also given to the decision making process leading to the designs
Design of a "Riesenrad" Ion Gantry for Hadrontherapy
The benefit of hadrontherapy can be maximized by offering the possibility to deliver the particle beam from any direction in space towards the patient with the help of a medical gantry. For carbon ions, their increased (magnetic) beam rigidity yields considerable structural difficulties and has so far prevented a practical realization of an ion gantry. The concept of a 'Riesenrad' ion gantry promises to provide an effective and efficient solution. The basic idea is to deflect the ion beam with a single 90° dipole, which rotates around the incoming beam axis, and direct it towards the eccentrically positioned patient cabin. Inside the cabin similar conditions as exist in a classical isocentric treatment room prevail. The practical design of such a Riesenrad gantry, its structural principles and its function are presented. The underlying beam optics and its integration into the mechanical structure are explained. Aspects of safety, and flexibility are discussed
Program for a novel ion gantry
In conjunction with the CERN-based development of a specially designed cancer therapy synchrotron (Proton-Ion Medical Machine Study - PIMMS), the need for the development of a facility equipped with an ion gantry emerged. Such a medical machine shall be capable of delivering a carbon ion beam virtually from every position and direction best suited for the treatment of the patient. Therefore the gantry allows to conform the delivered dose very closely to the tumour volume, minimise the dose deposited in healthy tissue and spare any critical organs. The technical challenges for the design are the high beam rigidity of the ion beam, requiring large and very heavy bending magnets, as well as the specified high precision of the whole system
Mechanical analysis and optimisation of large and highly-loaded bearing rollers For the "Riesenrad" Ion Gantry
A carbon ion gantry would allow the irradiation of cancer patients with carbon ions from any direction in space best suited for therapy. Till today, such a machine has not been built due to the expected size, mass and cost. A novel design, called "Riesenrad" ion gantry, promises to provide a competitive solution. The central part of the Riesenrad, which can rotate ± 90°, is supported (statically determinate) on pendular bearing units with two rollers each. High precision requirements for the structure rule out any plastic deformations in the area of contact. The present report describes the design of the highly-loaded rollers. In order to achieve a large contact area and a uniform distribution of contact stresses, a "barrel shape" for the rollers is proposed. An analysis using the finite element method (FEM) was performed to optimise the roller design, namely to establish the required crown roll (camber radius)
Development and Engineering Design of a Novel Exocentric Carbon-Ion Gantry for Cancer Therapy: The "Riesenrad" Gantry
Mechanical structures capable of delivering a therapy beam for cancer treatment from any direction to the patient are called medical gantries. Typically, a gantry rotates around the patient who is kept in the supine position (rotating gantries). In Europe several currently proposed clinic facilities for ion therapy want to install an ion gantry equipped with a pencil-beam scanning system. Such a treatment apparatus allows the optimisation of the dose-to-target conformity, but the active pencil-beam scanning increases the demands considerably on the beam transport accuracy. Usually, a sub-millimetre precision of the beam position at the patient (i.e. in the gantry isocentre) is required in order to treat tumours in the vicinity of critical organs, which is one of the main domains of ion therapy..
Proton-Ion Medical Machine Study (PIMMS), 2
The Proton-Ion Medical Machine Study (PIMMS) group was formed following an agreement between the Med-AUSTRON (Austria) and the TERA Foundation (Italy) to combine their efforts in the design of a cancer therapy synchrotron capable of accelerating either light ions or protons. CERN agreed to support and host this study in its PS Division. A close collaboration was also set up with GSI (Germany). The study group was later joined by Onkologie-2000 (Czech Republic). Effort was first focused on the theoretical understanding of slow extraction and the techniques required to produce a smooth beam spill for the conformal treatment of complex-shaped tumours with a sub-millimetre accuracy by active scanning with proton and carbon ion beams. Considerations for passive beam spreading were also included for protons. The study has been written in two parts. The more general and theoretical aspects are recorded in Part I and the specific technical design considerations are presented in the present volume, Part II. An accompanying CD-ROM contains supporting publications made by the team and data files for calculations. The PIMMS team started its work in January 1996 in the PS Division and continued for a period of four years
Large-Scale Model-Based Assessment of Deer-Vehicle Collision Risk
Ungulates, in particular the Central European roe deer Capreolus capreolus and the North American white-tailed deer Odocoileus virginianus, are economically and ecologically important. The two species are risk factors for deerâvehicle collisions and as browsers of palatable trees have implications for forest regeneration. However, no large-scale management systems for ungulates have been implemented, mainly because of the high efforts and costs associated with attempts to estimate population sizes of free-living ungulates living in a complex landscape. Attempts to directly estimate population sizes of deer are problematic owing to poor data quality and lack of spatial representation on larger scales. We used data on 74,000 deerâvehicle collisions observed in 2006 and 2009 in Bavaria, Germany, to model the local risk of deerâvehicle collisions and to investigate the relationship between deerâvehicle collisions and both environmental conditions and browsing intensities. An innovative modelling approach for the number of deerâvehicle collisions, which allows nonlinear environmentâdeer relationships and assessment of spatial heterogeneity, was the basis for estimating the local risk of collisions for specific road types on the scale of Bavarian municipalities. Based on this risk model, we propose a new âdeerâvehicle collision indexâ for deer management. We show that the risk of deerâvehicle collisions is positively correlated to browsing intensity and to harvest numbers. Overall, our results demonstrate that the number of deerâvehicle collisions can be predicted with high precision on the scale of municipalities. In the densely populated and intensively used landscapes of Central Europe and North America, a model-based risk assessment for deerâvehicle collisions provides a cost-efficient instrument for deer management on the landscape scale. The measures derived from our model provide valuable information for planning road protection and defining hunting quota. Open-source software implementing the model can be used to transfer our modelling approach to wildlifeâvehicle collisions elsewhere
Boom and bust of a moose population â a call for integrated forest management
This is the postprint version of the article. The published article can be located at www.springerlink.comThere is increasing pressure to manage forests
for multiple objectives, including ecosystem services and
biodiversity, alongside timber production. However, few
forests are currently co-managed for timber and wildlife,
despite potential economic and conservation benefits. We
present empirical data from a commercial Norway spruce
(
Picea abies
) and Scots pine (
Pinus sylvestris
) production
system in southern Norway in which moose (
Alces alces
)
are an important secondary product. Combining long-term
hunting and forestry records, we identified temporal vari-
ation in clear-felling over the past five decades, peaking in
the 1970s. Herbicide treatment of regenerating stands and a
fivefold increase in moose harvest has lead to a reduction in
availability of successional forest per moose of
[
90 %
since the 1960s. Field estimates showed that spraying with
the herbicide glyphosate reduced forage availability by 60
and 96 % in summer and winter, respectively, 4 years after
treatment. It also reduced moose use and habitat selection
of young spruce stands compared with unsprayed stands.
Together these lines of evidence suggest that forest man-
agement led to an increase in moose carrying capacity
during the 1970s and a subsequent decline thereafter. This
is likely to have contributed to observed reductions in moose population productivity in southern Norway and is
counter to sustainable resource management. We therefore
call for better integration and long-term planning between
forestry and wildlife management to minimise forest
damage and the development of large fluctuations in
ungulate populations
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