Energy Selection System Research Articles

Multi-criteria decision-based hybrid energy selection system using CRITIC weighted CODAS approach

A complex and multicriteria decision making (MCDM) problem arises in a bid to select the most appropriate hybrid energy system among several combinations in distributed electricity generation as it involves conflicting criteria that must be simultaneously considered. In this work, Criteria Importance Through Intercriteria Correlation (CRITIC) along with Combinative Distance-Based Assessment (CODAS) was employed to select a suitable hybrid energy system combination for water pumping from four conflicting alternatives of Biomass-Battery (S1), PV-Battery (S2), PV-Biomass (S3), and PV-Biomass-Battery (S4) by objective weight estimation. This was followed by a confirmation by the Additive Ratio Assessment (ARAS) method for the solution. The results presented show that CRITIC method reveals 0.275, 0.224, 0.248, and 0.252 as different weights of the four alternatives of S1, S2, S3, and S4, respectively. The ranking results reveal S4 as the best alternative based on an assessment score of 0.4693. The same hybrid system was confirmed by ARAS based on overall performance and degree of utility of 0.287697 and 0.823716, respectively.

Range shifter contribution to neutron exposure of patients undergoing proton pencil beam scanning.

Superficial targets require the use of the lowest energies within the available energy range in proton pencil-beam scanning (PBS) technique. However, the lower efficiency of the energy selection system at these energies and the requirement of a greater number of layers may represent disadvantages for this approach. The alternative is to use a range shifter (RS) at nozzle exit. However, one of the concerns of using this beamline element is that it becomes an additional source of neutrons that could irradiate organs situated far from the target. The purpose of this study is to assess the increase in neutron dose due to the RS in proton PBS technique. Additionally, an analytical model for the neutron production is tested. Two clinical plans, designed to achieve identical target coverage, were created for an anthropomorphic phantom. These plans consisted of a lateral field delivering an absorbed dose of 60Gy (RBE) to the target. One of the plans employed the RS. The MCNP code was used to simulate the plans, evaluating the distribution of neutron dose equivalent (Hn) and the equivalent dose in organ. In the plan with the RS plan, neutron production from both the patient and the RS were assessed separately. Hn values were also fitted versus the distance to field edge using a Gaussian function. Hn per prescription dose, in the plan using the RS, ranged between 1.4 and 3.7 mSv/Gy at the field edge, whereas doses at 40cm from the edge ranged from 9.9 to 32 μSv/Gy. These values are 1.2 to 10 times higher compared to those obtained without the RS. Both this factor and the contribution of neutrons originating from the RS increases with the distance from field edge. A triple-Gaussian function was able to reproduce the equivalent dose in organs within a factor of 2, although underestimating the values. The dose deposited in the patient by the neutrons originating from the RS predominantly affects areas away from the target (beyond approximately 25cm from field edge), resulting in a neutron dose equivalent of the order of mSv. This indicates an overall low neutron contribution from the use of RS in PBS.

Nonlinear Effects and Higher-Order Aberrations on Beam Optics of Energy Selection System for Proton Therapy

Nonlinear Effects and Higher-Order Aberrations on Beam Optics of Energy Selection System for Proton Therapy

Demonstration of momentum cooling to enhance the potential of cancer treatment with proton therapy

In recent years, there has been a considerable push towards ultrahigh dose rates in proton therapy to effectively utilize motion mitigation strategies and potentially increase the sparing of healthy tissue through the so-called FLASH effect. However, in cyclotron-based proton therapy facilities, it is difficult to reach ultrahigh dose rates for low-energy beams. The main reason for this lies in the large momentum spread that such beams have after reducing their energy to levels required for proton therapy, incurring large losses in conventionally used momentum or energy selection slits. Here we propose momentum cooling by using a wedge in the energy selection system (instead of a slit) to reduce the momentum spread of the beam without introducing substantial beam losses. We demonstrate this concept in our eye treatment beamline and obtain a factor of two higher transmission, which could eventually halve the treatment delivery time. Furthermore, we show that with a gantry design incorporating this feature, we can achieve almost a factor of 100 higher transmission for a 70 MeV beam compared with conventional cyclotron-based facilities. This concept could enhance the potential of proton therapy by opening up possibilities of treating new indications and reducing the cost.

Optical design and higher-order aberrations with the superconducting gantry based on limited ramping fields

One of the major challenges in proton therapy is the cost and scale of the treatment facility, which depends mainly on the dimensions of the gantry. A potential method that promises to make the gantry lighter and more compact is superconducting magnet technology. However, the rapid ramping requirements during energy modulation are the primary reason for magnet quenching. To alleviate these restrictions, we propose a superconducting bending section consisting of a TBA lattice for a gantry optical design. With only three magnetic field settings needed to deliver 70–200 MeV proton beams, it achieves ±10% large momentum acceptance owing to its significant dispersion function suppression capabilities. Another feature that contributes to reducing the footprint is the installation of a degrader on the proposed gantry, allowing the degraded beam to be guided directly to the isocenter without being filtered by the Energy Selection System. For verifying the feasibility of the concept, we assess the possibility of beam scraping in the beam path and beam spot distortion at the isocenter. These efforts are accomplished by modeling realistic field distributions with ANSYS Maxwell and then performing 7th-order transfer mapping through COSY Infinity. Regarding the influence of broad energy spread on beam depth dose distribution, TOPAS is used to simulate and compare the integrated depth dose for various therapeutic energies.

A novel intensity compensation method to achieve energy independent beam intensity at the patient location for cyclotron based proton therapy facilities

In cyclotron-based proton therapy facilities, an energy selection system is typically used to lower the beam energy from the fixed value provided by the accelerator (250/230 MeV) to the one needed for the treatment (230-70 MeV). Such a system has the drawback of increase beam emittance and introducing an energy-dependent beam current at the patient location, resulting in energy dependent beam intensity ratios of about 103 between high and low energies. This complicates treatment delivery and challenges patient safety systems. As such, we propose the use of a dual energy degrader method that can reduce beam intensity for high-energy beams. The first degrader is made of high Z material and the second is made of low Z material and are placed next to each other. For high energies (190-230 MeV), we use only the first degrader to increase beam emittance after the degrader and thus lose intensity in the emittance selection collimators. For intermediate energy beams (110-190 MeV) we use the combination of both degraders, whereas for low energy beams (70-110 MeV), only the second degrader limits the increase in emittance. With this approach, energy-independent beam intensities at the patient location can be achieved, whilst localizing beam losses around the degrader.

Achromatic beamline design for a laser-driven proton therapy accelerator

A new laser-driven proton therapy facility is being designed by Peking University. The protons will be produced by laser--plasma interaction, using a 2-PW laser to reach proton energies up to 100 MeV. We hope that the construction of this facility will promote the real-world applications of laser accelerators. Based on the experimental results and design experience of existing devices in Peking University, we propose a beam transmission system which is suitable for the beam produced by laser acceleration, and demonstrate its feasibility through theoretical simulation. It is designed with two transport lines to provide both horizontal and vertical irradiation modes. We have used a locally-achromatic design method with new canted-cosine-theta (CCT) magnets. These two measures allow us to mitigate the negative effects of large energy spread produced by laser-acceleration, and to reduce the overall weight of the vertical beamline. The beamline contains a complete energy selection system, which can reduce the energy spread of the laser-accelerated beam enough to meet the application requirements. The users can select the proton beam energy within the range 40--100 MeV, which is then transmitted through the rest of the beamline. A beam spot with diameter of less than 15 mm and energy spread of less than 5% can be provided at the horizontal and vertical irradiation targets.

Geometry optimisation of graphite energy degrader for proton therapy

Introduction: Cyclotron-based proton therapy facilities use an energy degrader of variable thickness to deliver beams of the different energies required by a patient treatment plan; scattering and straggling in the degrader give rise to an inherent emittance increase and subsequent particle loss in the downstream energy-selection system (ESS). Here we study alternative graphite degrader geometries and examine with Monte-Carlo simulations the induced emittance growth and consequent particle transmission.Methods: We examined the conventional multiple-wedge degrader used in the Paul Scherrer Institute PROSCAN proton therapy system, the equivalent parallel-sided degrader, and a single block degrader of equivalent thickness. G4Beamline Monte-Carlo tracking of protons was benchmarked against measurements of the existing degrader for proton energies from 75 to 230 MeV, and used to validate simulations of the alternative geometries.Results: Using a careful calculation of the beam emittance growth, we determined that a single-block degrader placed close to the collimators of the ESS is expected to deliver significantly larger transmission, up to 17% larger at 150 MeV. At the lowest deliverable of 75 MeV there is still a clear improvement in beam transmission.Conclusions: Whilst dose rates are not presently limited on the PROSCAN system at higher energies, a single-block degrader offers the ability to access either lower energies for treatment or a larger dose rate at 75 MeV in case transmission optimisation is desired. Single-block degraders should be considered for the delivery of low-energy protons from a cyclotron-based particle therapy system.

Design and Optimization Based on Monte Carlo Method of a Range Shifter for Proton Therapy

A proton therapy facility based on an isochronous superconducting cyclotron is under constructed at the Proton Therapy Facility of the Huazhong University of Science and Technology. Due to the limitation of minimum energy extracted by the energy selection system in the upstream beamline, a range shifter is installed at the end of the nozzle to further decrease the proton beam energy so that the shallow-seated tumors can be treated. In this paper, the physical structure, energy degradation scheme, and material optimization selection of the range shifter are discussed and analyzed by Monte Carlo simulation software Geant4 and FLUKA. At the same time, the treatment outcome on the energy degradation process and its influence on the synthesis of spread-out Bragg peak (SOBP) in the treatment plan system after the application of the range shifter are analyzed. The results show that by using a high-density polyethylene energy-degrading plate with a thickness of 42.35 mm, combined with two 30-mm copper collimators, the range shifter can achieve a good energy-degradation effect while significantly reducing the beam horizontal penumbra at the edge of the radiation field. At the same time, the addition of the range shifter can reduce the number of the energy level required to form the SOBP and shorten the treatment time, but it will inevitably lead to a slight increase in the longitudinal penumbra.

Radiation shielding design of a compact single-room proton therapy based on synchrotron

A synchrotron-based proton therapy (PT) facility that conforms with the requirement of future development trend in compact PT can be operated without an energy selection system. This article demonstrates a novel radiation shielding design for this purpose. Various FLUKA-based Monte Carlo simulations have been performed to validate its feasibility. In this design, two different shielding scenarios (3-m-thick concrete and 2-m-thick iron–concrete) are proved able to reduce the public annual dose to the limit of 0.1 mSv/year. The calculation result shows that the non-primary radiation from a PT system without an inner shielding wall complies with the IEC 60601-2-64 international standard, making a single room a reality. Moreover, the H/D value of this design decreases from 2.14 to 0.32 mSv/Gy when the distance ranges from 50 to 150 cm from the isocenter, which is consistent with the previous result from another study. By establishing a typical time schedule and procedures in a treatment day for a single room in the simulation, a non-urgent machine maintenance time of 10 min after treatment is recommended, and the residual radiation level in most areas can be reduced to 2.5 μSv/h. The annual dose for radiation therapists coming from the residual radiation is 1 mSv, which is 20% of the target design. In general, this shielding design ensures a low cost and compact facility compared with the cyclotron-based PT system.

Large energy acceptance gantry for proton therapy utilizing superconducting technology

When using superconducting (SC) magnets in a gantry for proton therapy, the gantry will benefit from some reduction in size and a large reduction in weight. In this contribution we show an important additional advantage of SC magnets in proton therapy treatments. We present the design of a gantry with a SC bending section and achromatic beam optics with a very large beam momentum acceptance of 15% (corresponding to about 30% in the energy domain). Due to the related very large energy acceptance, approximately 70% of the treatments can be performed without changing the magnetic field for synchronization with energy modulation. In our design this is combined with a 2D lateral scanning system and a fast degrader mounted in the gantry, so that this gantry will be able to perform pencil beam scanning with very rapid energy variations at the patient, allowing a significant reduction of the irradiation time.We describe the iterative process we have applied to design the magnets and the beam transport, for which we have used different codes. COSY Infinity and OPAL have been used to design the beam transport optics and to track the particles in the magnetic fields, which are produced by the magnets designed in Opera. With beam optics calculations we have derived an optimal achromatic beam transport with the large momentum acceptance of the proton pencil beam and we show the agreement with particle tracking calculations in the 3D magnetic field map.A new cyclotron based facility with this gantry will have a significantly smaller footprint, since one can refrain from the standard degrader and energy selection system behind the cyclotron. In the treatments, this gantry will enable a very fast proton beam delivery sequence, which may be of advantage for treatments in moving tissue.

Design of a high energy Thomson Parabola ion spectrometer for the ELIMAIA beamline

The ELIMAIA beamline has been installed in the experimental hall dedicated to ion acceleration at ELI-Beamlines. In this paper we propose a design of a first upgrade of the beamline which will allow the use of the already installed energy selection system as a Thomson Parabola spectrometer, which is a key diagnostics for laser-accelerated ion beams. Such ion spectrometer will allow to detect protons up to 300 MeV protons and carbons ions up to 75 MeV per nucleon. Nominal performances of this spectrometer are discussed and compared with calibration of the first magnet of the chicane. Moreover, the main issues in its realization are highlighted and solutions are proposed.

Analysis and Design of an Energy Verification System for SC200 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.

Beam optics study for energy selection system of SC200 superconducting proton cyclotron

To meet the demands on proton therapy in Russia and China, JINR and ASIPP have started to develop a proton therapy facility based on an isochronous superconducting proton accelerator. A 200 MeV/500 nA proton beam will be extracted from the SC200 superconducting proton cyclotron. Due to the energy of the cyclotron being fixed, an energy selection system (ESS) is employed to degrade such energy in order to match the particle energy to a shallower depth. In this article, calculation of beam optics, analysis of beam transmission, and correction of orbit distortion are presented. Studies show that the main factors influencing transmission efficiency of the SC200 ESS beamline are the degrader, collimator, slit, vacuum system, beam diagnostic system, and trajectory correction system. Through the beam optics study, the designed ESS beamline can provide 70–200 MeV proton beam to a treatment room, with a maximum emittance of 24 π mm mrad. Also, the controllable momentum spread ranges from 0.1 to 1.0%, which is equivalent to an energy spread from 0.193 to 1.93%. The transmission efficiency about 0.204% can be obtained when the emittance is 24 π mm mrad with an energy spread of ± 0.6%.

Design of Prototype Magnets for HUST Proton Therapy Beamline

A proton therapy facility with two 360° gantry treatment rooms and one fixed beamline is under development at the Huazhong University of Science and Technology (HUST), which is based on an isochronous superconducting cyclotron. The energy is modulated in the range of 70–240 MeV with an energy selection system. In this paper, we report the main design specifications of the beamline in the HUST-PTF project, in which the main features are the intensity suppression scheme beamline. Two prototype magnets (one quadrupole and one dipole) used in the beamline are also studied and presented. Two-dimensional contour optimization and pole-end chamfer iteration are used to minimize the harmonic errors of the integral field. Finally, both the field homogeneity and multipole errors achieve the precision requirement over the operating field range.

Design of Gantry Beamline for HUST Proton Therapy Facility

A proton therapy facility with two 360° gantry treatment rooms and one fixed beamline is under development in the Huazhong University of Science and Technology, which is based on the isochronous superconducting cyclotron scheme. This paper presents the beam optics and main magnetic elements including dipoles, quadrupoles, and fast scanning magnets of the gantry beamline. In addition, the energy selection system will be introduced, which enables fast energy modulation of proton beam between 70 and 240 MeV.

Transmission calculation and intensity suppression for a proton therapy system

A proton therapy project HUST-PTF (HUST Proton Therapy Facility) based on a 250 MeV isochronous superconducting cyclotron is under development in Huazhong University of Science and Technology (HUST). In this paper we report the main design features of the beam line in HUST-PTF project. The energy selection system (ESS) for energy modulation is discussed in detail, including the collimators, momentum slit and transmission calculation. Due to significant difference among the transmissions of ESS for different energies, the intensity suppression scheme by defocusing beam at high energies on collimators in the beam line is proposed and discussed. Finally, the ratios of beam intensities between low and high energies are expected to be controlled within 10 to meet the clinical requirement, and the beam optics of each energy step after intensity suppression is studied respectively.

Design of the prototype of a beam transport line for handling and selection of low energy laser-driven beams

A first prototype of transport beam-line for laser-driven ion beams to be used for the handling of particles accelerated by high-power laser interacting with solid targets has been realized at INFN. The goal is the production of a controlled and stable beam in terms of energy and angular spread. The beam-line consists of two elements: an Energy Selection System (ESS), already realized and characterized with both conventional and laser-accelerated beams, and a Permanent Magnet Quadrupole system (PMQ) designed, in collaboration with SIGMAPHI (Fr), to improve the ESS performances. In this work a description of the ESS system and some results of its characterization with conventional beams are reported, in order to provide a complete explanation of the acceptance calculation. Then, the matching with the PMQ system is presented and, finally, the results of preliminary simulations with a realistic laser-driven energy spectrum are discussed demonstrating the possibility to provide a good quality beam downstream the systems.

A simple PMMA phantom for daily QA energy checks in proton therapy

Introduction Beam energy measurements are one of the most important data that every radiotherapy facility has to collect periodically as constancy check. In proton therapy, due to the energy selection system and to the shape of the Bragg peak, this check has to be performed daily. Purpose To demonstrate that reliable daily proton energy verification is achievable using a 2D array of ionization chambers (IC) combined with our PMMA phantom. Material and methods The PMMA phantom is provided with three couples of wedges: thanks to these, Bragg peak is sampled at different depths and the image becomes a transposition on the transverse plane of the depth dose. Coupled wedges are necessary to compensate for set-up errors. Three wedges of different slopes (the first and lowest one is for energy from 70 to 100 MeV, the middle one from 100 to 140 MeV and the third and highest one from 140 to 226 MeV) are used to spread the depth dose of every single checked energy in a way that the distal penumbra can be properly detected by an adequate number of IC in the 2D Array device. Results A sensitivity test showed that the phantom is able to detect range variations greater than the threshold (2 mm). Conclusions We designed and built a reliable phantom for the range verification. Moreover, the costs of this phantom are very low compared to other commercial solutions used for range verification in proton therapy.

Design of a large acceptance, high efficiency energy selection system for the ELIMAIA beam-line

A magnetic chicane based on four electromagnetic dipoles is going to be realized by INFN-LNS to be used as an Energy Selection System (ESS) for laser driven proton beams up to 300 MeV and C6+ up to 70 MeV/u. The system will provide, as output, ion beams with a contrallable energy spread varying from 5% up to 20% according to the aperture slit size. Moreover, it has a very wide acceptance in order to ensure a very high transmission efficiency and, in principle, it has been designed to be used also as an active energy modulator. This system is the core element of the ELIMED (ELI-Beamlines MEDical and Multidisciplinary applications) beam transport, dosimetry and irradiation line that will be developed by INFN-LNS (It) and installed at the ELI-Beamlines facility in Prague (Cz). ELIMED will be the first user's open transport beam-line where a controlled laser-driven ion beam will be used for multidisciplinary research. The definition of well specified characteristics, both in terms of performance and field quality, of the magnetic chicane is crucial for the system realization, for the accurate study of the beam dynamics and for the proper matching with the Permanent Magnet Quadrupoles (PMQs) used as a collection system already designed. Here, the design of the magnetic chicane is described in details together with the adopted solutions in order to realize a robust system form the magnetic point of view. Moreover, the first preliminary transport simulations are also described showing the good performance of the whole beam line (PMQs+ESS).