scholarly journals A new emittance selection system to maximize beam transmission for low‐energy beams in cyclotron‐based proton therapy facilities with gantry

2021 ◽  
Author(s):  
Vivek Maradia ◽  
David Meer ◽  
Damien Charles Weber ◽  
Antony John Lomax ◽  
Jacobus Maarten Schippers ◽  
...  
Keyword(s):  
Proton Therapy ◽  
Low Energy ◽  
Selection System ◽  
Beam Transmission

scholarly journals Analysis and Design of an Energy Verification System for SC200 Proton Therapy Facility

Electronics ◽  
2019 ◽  
Vol 8 (5) ◽  
pp. 541 ◽  
Author(s):  
Pengyu Wang ◽  
Jinxing Zheng ◽  
Yuntao Song ◽  
Wuquan Zhang ◽  
Ming Wang
Keyword(s):  
Magnetic Field ◽  
Proton Beam ◽  
Proton Therapy ◽  
Hall Probe ◽  
Selection System ◽  
Maximum Width ◽  
Verification Method ◽  
Analysis And Design ◽  
Proton Beam Energy ◽  
Proton Therapy Facility

The purpose of this study is to provide an energy verification method for the nozzle of the SC200 proton therapy facility to ensure safe redundancy of treatment. This paper first introduces the composition of the energy selection system of the SC200 proton therapy facility. Secondly, according to IEC60601 standard, the energy verification requirement that correspond to 1 mm error in water is presented. The allowable difference between the measured magnetic field and the reference are calculated based on the energy verification requirements to select the field resolution of the Hall probe. To ensure accuracy and stability, two Hall probes are mounted on the dipole to monitor the magnetic field strength to verify the proton beam energy in real time. In addition, the test results of the residual field of the dipole show that the probe system meets the accuracy requirements of energy verification. Furthermore, the maximum width of the slit of the energy selection system in accordance with the IEC standard at the corresponding energy is calculated and compared with the actual position of the movable slit to verify the momentum divergence of the proton beam. Finally, we present an energy verification method.

scholarly journals Exploring the advantages of intensity-modulated proton therapy: experimental validation of biological effects using two different beam intensity-modulation patterns

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Duo Ma ◽  
Lawrence Bronk ◽  
Matthew Kerr ◽  
Mary Sobieski ◽  
Mei Chen ◽  
...  
Keyword(s):  
Proton Therapy ◽  
Biological Effects ◽  
High Energy ◽  
Intensity Modulation ◽  
Low Energy ◽  
Delivery Strategy ◽  
Intensity Modulated Proton Therapy ◽  
Intensity Modulated ◽  
Flat Dose ◽  
Beam Delivery

Abstract In current treatment plans of intensity-modulated proton therapy, high-energy beams are usually assigned larger weights than low-energy beams. Using this form of beam delivery strategy cannot effectively use the biological advantages of low-energy and high-linear energy transfer (LET) protons present within the Bragg peak. However, the planning optimizer can be adjusted to alter the intensity of each beamlet, thus maintaining an identical target dose while increasing the weights of low-energy beams to elevate the LET therein. The objective of this study was to experimentally validate the enhanced biological effects using a novel beam delivery strategy with elevated LET. We used Monte Carlo and optimization algorithms to generate two different intensity-modulation patterns, namely to form a downslope and a flat dose field in the target. We spatially mapped the biological effects using high-content automated assays by employing an upgraded biophysical system with improved accuracy and precision of collected data. In vitro results in cancer cells show that using two opposed downslope fields results in a more biologically effective dose, which may have the clinical potential to increase the therapeutic index of proton therapy.

scholarly journals Innovations and the Use of Collimators in the Delivery of Pencil Beam Scanning Proton Therapy

2021 ◽  
Vol 8 (1) ◽  
pp. 73-83
Author(s):  
Daniel E. Hyer ◽  
Laura C. Bennett ◽  
Theodore J. Geoghegan ◽  
Martin Bues ◽  
Blake R. Smith
Keyword(s):  
Proton Therapy ◽  
Spot Size ◽  
Low Energy ◽  
Healthy Tissue ◽  
Pencil Beam ◽  
New Paradigm ◽  
Beam Scanning ◽  
Multileaf Collimators ◽  
Pencil Beam Scanning ◽  
Tissue Sparing

Abstract Purpose The development of collimating technologies has become a recent focus in pencil beam scanning (PBS) proton therapy to improve the target conformity and healthy tissue sparing through field-specific or energy-layer–specific collimation. Given the growing popularity of collimators for low-energy treatments, the purpose of this work was to summarize the recent literature that has focused on the efficacy of collimators for PBS and highlight the development of clinical and preclinical collimators. Materials and Methods The collimators presented in this work were organized into 3 categories: per-field apertures, multileaf collimators (MLCs), and sliding-bar collimators. For each case, the system design and planning methodologies are summarized and intercompared from their existing literature. Energy-specific collimation is still a new paradigm in PBS and the 2 specific collimators tailored toward PBS are presented including the dynamic collimation system (DCS) and the Mevion Adaptive Aperture. Results Collimation during PBS can improve the target conformity and associated healthy tissue and critical structure avoidance. Between energy-specific collimators and static apertures, static apertures have the poorest dose conformity owing to collimating only the largest projection of a target in the beam's eye view but still provide an improvement over uncollimated treatments. While an external collimator increases secondary neutron production, the benefit of collimating the primary beam appears to outweigh the risk. The greatest benefit has been observed for low- energy treatment sites. Conclusion The consensus from current literature supports the use of external collimators in PBS under certain conditions, namely low-energy treatments or where the nominal spot size is large. While many recent studies paint a supportive picture, it is also important to understand the limitations of collimation in PBS that are specific to each collimator type. The emergence and paradigm of energy-specific collimation holds many promises for PBS proton therapy.

Application of very low energy neutron radiography with energy selection system using 4Qc(4m) supermirror

2005 ◽  
Vol 542 (1-3) ◽  
pp. 61-67 ◽  
Author(s):  
Yuji Kawabata ◽  
Masahiro Hino ◽  
Takafumi Nakano ◽  
Hiroaki Sunohara ◽  
Uzuki Matsushima ◽  
...  
Keyword(s):  
Neutron Radiography ◽  
Low Energy ◽  
Selection System ◽  
Energy Neutron

Very Low Energy Neutron Radiography with Neutron Energy Selection System for Variable Image Contrast

2004 ◽  
Vol 270-273 ◽  
pp. 1291-1296 ◽  
Author(s):  
Y. Kawabata ◽  
T. Nakano ◽  
M. Hino ◽  
T. Oku ◽  
J. Susuki ◽  
...  
Keyword(s):  
Neutron Energy ◽  
Neutron Radiography ◽  
Image Contrast ◽  
Low Energy ◽  
Selection System ◽  
Energy Neutron

Experimental validation of the filtering approach for dose monitoring in proton therapy at low energy

2008 ◽  
Vol 24 (2) ◽  
pp. 102-106 ◽  
Author(s):  
F. Attanasi ◽  
N. Belcari ◽  
M. Camarda ◽  
A. Del Guerra ◽  
S. Moehrs ◽  
...  
Keyword(s):  
Proton Therapy ◽  
Experimental Validation ◽  
Low Energy ◽  
Dose Monitoring ◽  
Filtering Approach

Dissociated Σ=27 boundaries in silicon

1988 ◽  
Vol 46 ◽  
pp. 624-625
Author(s):  
A. Garg ◽  
W.A.T. Clark ◽  
J.P. Hirth
Keyword(s):  
Electron Diffraction ◽  
Local Minimum ◽  
Boundary Energy ◽  
Coincidence Site Lattice ◽  
Boundary Plane ◽  
Low Energy ◽  
Theoretical Understanding ◽  
Site Lattice ◽  
Kikuchi Pattern ◽  
Analysis Techniques

In the last twenty years, a significant amount of work has been done in the theoretical understanding of grain boundaries. The various proposed grain boundary models suggest the existence of coincidence site lattice (CSL) boundaries at specific misorientations where a periodic structure representing a local minimum of energy exists between the two crystals. In general, the boundary energy depends not only upon the density of CSL sites but also upon the boundary plane, so that different facets of the same boundary have different energy. Here we describe TEM observations of the dissociation of a Σ=27 boundary in silicon in order to reduce its surface energy and attain a low energy configuration.The boundary was identified as near CSL Σ=27 {255} having a misorientation of (38.7±0.2)°/[011] by standard Kikuchi pattern, electron diffraction and trace analysis techniques. Although the boundary appeared planar, in the TEM it was found to be dissociated in some regions into a Σ=3 {111} and a Σ=9 {122} boundary, as shown in Fig. 1.

Transfer optics for high spatial resolution electron spectroscopy

1988 ◽  
Vol 46 ◽  
pp. 666-667
Author(s):  
G. G. Hembree ◽  
Luo Chuan Hong ◽  
P.A. Bennett ◽  
J.A. Venables
Keyword(s):  
Magnetic Field ◽  
Scanning Transmission Electron Microscope ◽  
Low Energy ◽  
Objective Lens ◽  
State University ◽  
Arizona State University ◽  
Initial Field ◽  
Resolution Electron ◽  
Scanning Transmission ◽  
Low Energy Electrons

A new field emission scanning transmission electron microscope has been constructed for the NSF HREM facility at Arizona State University. The microscope is to be used for studies of surfaces, and incorporates several surface-related features, including provision for analysis of secondary and Auger electrons; these electrons are collected through the objective lens from either side of the sample, using the parallelizing action of the magnetic field. This collimates all the low energy electrons, which spiral in the high magnetic field. Given an initial field Bi∼1T, and a final (parallelizing) field Bf∼0.01T, all electrons emerge into a cone of semi-angle θf≤6°. The main practical problem in the way of using this well collimated beam of low energy (0-2keV) electrons is that it is travelling along the path of the (100keV) probing electron beam. To collect and analyze them, they must be deflected off the beam path with minimal effect on the probe position.

Performance Evaluation of a Novel Type of Low-Energy Electron Microscope

1990 ◽  
Vol 48 (1) ◽  
pp. 354-355
Author(s):  
Bertholdand Senftinger ◽  
Helmut Liebl
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Field Strength ◽  
Numerical Aperture ◽  
Low Energy ◽  
Energy Electron ◽  
High Resolution Imaging ◽  
Lens System ◽  
Resolution Imaging ◽  
Low Energy Electron

During the last few years the investigation of clean and adsorbate-covered solid surfaces as well as thin-film growth and molecular dynamics have given rise to a constant demand for high-resolution imaging microscopy with reflected and diffracted low energy electrons as well as photo-electrons. A recent successful implementation of a UHV low-energy electron microscope by Bauer and Telieps encouraged us to construct such a low energy electron microscope (LEEM) for high-resolution imaging incorporating several novel design features, which is described more detailed elsewhere.The constraint of high field strength at the surface required to keep the aberrations caused by the accelerating field small and high UV photon intensity to get an improved signal-to-noise ratio for photoemission led to the design of a tetrode emission lens system capable of also focusing the UV light at the surface through an integrated Schwarzschild-type objective. Fig. 1 shows an axial section of the emission lens in the LEEM with sample (28) and part of the sample holder (29). The integrated mirror objective (50a, 50b) is used for visual in situ microscopic observation of the sample as well as for UV illumination. The electron optical components and the sample with accelerating field followed by an einzel lens form a tetrode system. In order to keep the field strength high, the sample is separated from the first element of the einzel lens by only 1.6 mm. With a numerical aperture of 0.5 for the Schwarzschild objective the orifice in the first element of the einzel lens has to be about 3.0 mm in diameter. Considering the much smaller distance to the sample one can expect intense distortions of the accelerating field in front of the sample. Because the achievable lateral resolution depends mainly on the quality of the first imaging step, careful investigation of the aberrations caused by the emission lens system had to be done in order to avoid sacrificing high lateral resolution for larger numerical aperture.

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