Previous studies show remarkable differences in the simulation of electron depth dose profiles of ruthenium eye plaques. We examined the influence of the scoring and simulation geometry, the source ...spectrum and the multiple scattering algorithm on the depth dose profile using GEANT4. The simulated absolute dose deposition agrees with absolute dose data from the manufacturer within the measurement uncertainty. Variations in the simulation geometry as well as the source spectrum have only a small influence on the depth dose profiles. However, the multiple scattering algorithms have the largest influence on the depth dose profiles. They deposit up to 20% less dose compared to the single scattering implementation. We recommend researchers who are interested in simulating low- to medium-energy electrons to examine their simulation under the influence of different multiple scattering settings. Since the simulation and scoring geometry as well as the exact physics settings are best described by the source code of the application, we made the code publicly available.
An xyz-measuring table with a modular design has been developed for the determination of the individual 3D dose rate distributions of different brachytherapy sources requiring a high spatial ...resolution and reproducibility. The instrumental setup consists of a plastic scintillator detector system and the xyz-measuring table for guiding the detector across the radioactive sources. For this purpose, a micro positioning system with piezo inertial drives is chosen, providing a step width of 450 nm. To ensure a high reproducibility and accuracy better than 1 μm, an exposed linear encoder controls the positioning. The successful operation of the xyz-measuring table is exemplarily shown by measurements of dose profiles of two brachytherapy sources, an ophthalmic plaque and a radioactive seed. The setup allows a fully automated quality assurance of ophthalmic plaques and radioactive seeds under clinical conditions and can be extended to other (brachytherapy) sources of similar dimensions.
The treatment of moving targets is a challenging task using high conformal radiation techniques such as pencil beam scanning (PBS) proton therapy and requires adequate motion mitigation. Recent ...guidelines propose 4D robust optimization to mitigate motion artefacts in PBS therapy of thoracic malignancies. However, the availability of dosimetric analyses supporting this recommendation is limited and even non-existing for other tumour sites. The objective of this study was therefore to analyse the effectiveness of 4D robust optimization for hepatocellular carcinoma (HCC), representative for moving abdominal targets. These are usually less affected by uncertainties due to tissue heterogeneities than thoracic targets. 4D robustly optimized plans were compared with beam-specific margin plans for 6 HCC patients based on 4D dynamic accumulated doses (4DDD). 4DDD computations were conducted in RayStation with an experimentally validated routine including a site-specific beam time model. Contrary to expectations based on thoracic studies, 4D robust optimization did not yield a more homogeneous target coverage except for shallow targets close to the ribs. A clear advantage of 4D robust optimization is the sparing of normal tissue. The average dose to the normal liver could be reduced by up to 12%.
Radiation hardness of the LHCb Outer Tracker van Eijk, D.; Bachmann, S.; Bauer, Th ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2012, Letnik:
685
Journal Article
Recenzirano
Odprti dostop
This paper presents results on the radiation hardness of the LHCb Outer Tracker (OT) during LHC operation in 2010 and 2011. Modules of the OT have shown to suffer from ageing effects that lead to ...gain loss, after irradiation in the laboratory. Under irradiation at moderate intensities an insulating layer is formed on the anode wire of the OT straw cells. This ageing effect is caused by contamination of the counting gas due to outgassing of the glue used in the construction of the OT modules. Two methods to monitor gain stability in the OT are presented: module scans with radioactive sources and the study of hit efficiency as a function of amplifier threshold. No gain loss is observed after receiving 1.3fb−1 of integrated luminosity corresponding to an integrated charge of 0.055C/cm in the hottest spot of the detector.
Tau physics at future machines Spaan, B.
Nuclear physics. Section B, Proceedings supplement,
05/1997, Letnik:
55, Številka:
3
Journal Article
Recenzirano
The prospects on Tau physics at future machines will be discussed, with future machines under consideration are B-factories and a τ/charm factory. Based on the experiences maded at existing ...experiments, the focus of this talk will be the issue of precision measurements and the need for the reduction of systematic errors.
The straw tube technology for the LHCb outer tracking system Bachmann, S.; Bagaturia, I.; Deppe, H. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2004, Letnik:
535, Številka:
1
Journal Article
Recenzirano
Odprti dostop
For the outer tracking system of the LHCb spectrometer 53.760 straws of 2.5
m length will be used. They are arranged in detector modules of 5
m length and 0.34
m width. The envisaged spatial ...resolution over the entire active area is 200
μ
m resulting in stringent requirements on the accuracy for the module construction.
In this paper we discuss the optimisation of the straws, design and construction of detector modules. The long-term operation properties of straws in two different counting gases, Ar/CO
2
(70/30) and Ar/CO
2
/CF
4
(75/10/15), are compared.
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