Collimation Method Research Articles

Engineering implementation of permanent magnet uniform spreading system for 3 MeV electron beam accelerator

Electron radiation technology, a significant application of non-power civil nuclear technology, opens up various research opportunities for electron beam accelerators as radiation sources. This paper introduces the engineering implementation of a permanent magnet uniform spreading system for the 3 MeV electron beam accelerator. The system is designed to improve radiation homogeneity, which is a crucial performance parameter in the radiation processing. The paper firstly investigates the collimation of magnets and beam spot in electron beam accelerators and proposes a novel collimation method. In addition, we also address various engineering implementation challenges encountered during the practical application of the uniform spreading system's permanent magnet devices. As a prerequisite for the application of uniform spreading system, a long-term stability experiment is conducted on the permanent magnets in radiation environments. The engineering feasibility of the uniform spreading system is ultimately verified by assessing the radiation homogeneity at the target using radiation dose tablets.

Development of fixed-point two-degree-of-freedom angular error measurement system with precision improvement function.

In the field of precision industries, measuring micro-angular errors plays a crucial role in improving the accuracy of equipment. Therefore, this study aims to develop a two-degree-of-freedom (two-DOF) angular error measurement system for simultaneously measuring the assembly angle errors of the bond head in a die bonding machine. This system is based on the laser collimation method and constructed by using components such as a fiber laser and position-sensitive detectors. It utilizes the angular drift compensation of the laser beam and averaging function to improve the measurement accuracy. In addition, the mathematical model of the proposed system was established by using skew-ray tracing. Through experiments, the measuring accuracy of ±0.25 arcsec and measuring repeatability of 0.3 arcsec could be achieved.

Topological structure effects of Laguerre-Gaussian laser on self-collimation acceleration mechanism

Energetic plasma beams can be generated through the interaction between a short-pulse high-intensity laser and solid target. However, obtaining collimated plasma beams with low divergence remains challenging. In this study, we devised a self-collimation scheme driven by a topologically structured Laguerre–Gaussian (LG) laser that irradiates a thin target in three-dimensional particle-in-cell simulations. It was observed that a high-density and narrow plasma beam could be formed by the intrinsic hollow intensity distribution of the LG laser. A magnetic tunnel was generated around the beam and collimated the plasma beam within a radius of hundreds of nanometers. This collimation can be enhanced by increasing the topological charge from l = 1 to l = 3 and then destroyed for a larger l. The collimation method is promising in applications requiring well-collimated energetic plasma beams, such as indirect drive inertial con-finement fusion, laboratory astrophysics, and radiation therapy.

Numerical modeling of mapping of Martian epithermal neutron emission: Applications to FREND investigation onboard ESA’s Trace Gas Orbiter

Neutron telescope FREND is operating onboard ESA TGO mission from May 2018 till present. The instrument measures epithermal neutron flux from the Martian surface. Measured variations of the neutron flux may be used to determine hydrogen abundance in the soil usually interpreted as a water/water ice. The unique design of the instrument provides measurements of the neutron flux with a spatial resolution that is much higher than the resolution of previous neutron spectrometers operating on orbit around Mars on board the NASA Mars Odyssey spacecraft. It is known that the spatial resolution of a neutron spectrometer in an orbit around Mars is determined not only by the parameters of the detectors, presence or absence of additional modules to improve the resolution, the orbital altitude of the spacecraft, but also by the fact that Mars has an atmosphere that scatters some of the neutrons that emerge from the Martian surface. One of the ways to increase the spatial resolution of orbital neutron detectors is the passive collimation method using neutron-absorbing substances. In this paper we consider the results of numerical modeling of parameters of the collimated instrument in order to determine its spatial resolution, taking into account the presence of the Martian atmosphere. The contribution of neutrons passing through the collimator walls to the total counting rate and how they affect the estimation of the hydrogen/water concentration in the soil are also considered. Therefore, a method was developed to take into account the imperfect absorbing properties of the collimator and to clear the measured signal from the contribution of neutrons that passed through the collimator wall. Comparison of the spatial resolution of non-collimated and collimated instruments is discussed. Moreover, the results obtained with the conventional method of data processing are compared with the results of developed method, which takes into account the contribution of non-collimated neutrons. The advantage of the results obtained by the developed method is shown.

Anti-mutation load and error stability of a large aperture lens based on parallel collimation locking.

Based on the lens of spatial filter parallel auxiliary assembly and collimation method, aiming at the unloading and locking problem of the filter lens after collimating, a lens parallel adjustable axial locking structure was proposed. A special elastic chuck structure was designed to realize clamping axial friction locking; each branch realized interference fit, and the adjustable structure of "line-line-line" contact realized equivalent fixation through spring pre-tightening. Compared with radial locking, the abrupt error of the axial locking lens in the unloading process of a collimating auxiliary machine was small, and the posture state maintenance and structural response stability were strong. The established homogeneous transformation matrix (HTM) and lens global error showed that the pose torsion roll error of the radial locking structure was significantly suppressed. The relative stability experiment showed that the angular drift error of the lens axial locking structure was ± 0.2 µrad. The design effectively improved the unloading anti-mutation characteristics and stability of the filter lens, which provided an experimental basis for the application of intelligent collimation assisted assembly and adjustment scheme in the upgrading of a high-power laser device.

Radiation-Shielding Devices: The Best Combination for Spine Interventional Procedures

PurposeAlthough many studies have examined the efficiency of various protective devices for reducing the dose of radiation exposure to physicians during interventional pain procedures, no study has compared the protective effect of these devices when they are used in combination. The purpose of this prospective experimental study was to determine the best combination of radiation-shielding devices. Materials and MethodsUsing anthropomorphic phantoms of a physician and patient, we measured the radiation protection efficiency (RPE) of each of the following protection methods and in combination during C-arm–guided simulated lumbar epidural injection: (a) personal protective equipment (PPE), (b) bedside curtain shield (Curtain), (c) x-ray tube filter (Filter), and (d) fluoroscopic collimation method (Collimation). We measured exposure doses using personal electronic dosimeters at the eye, thyroid, and gonad levels for 1 minute. Each experiment was repeated 15 times. ResultsThe radiation exposure dose and RPE with the best single-, double-, and triple-protection methods were as follows: PPE for the single-protection method (11.82 μSv/min, 80.04%), PPE + Collimation for the double-combination method (4.68 μSv/min, 92.09%), and PPE + Collimation + Curtain for the triple-combination method (3.08 μSv/min, 93.39%). Additionally, PPE + Collimation + Curtain + Filter for the quadruple-combination method resulted in a radiation exposure and RPE of 2.91 μSv/min and 93.61%, respectively, compared with nonprotection. ConclusionsThe best single-, double-, and triple-protection method was PPE, PPE + Collimation, and PPE + Collimation + Curtain, respectively. While preparing protective equipment, we recommend prioritizing equipment in this order.

Research on X-ray Fluorescence Enhanced Fluoroscopy Imaging Technology

Chest X-ray fluoroscopy is a commonly used medical imaging method, which has a wide range of applications in the diagnosis of lung diseases and other fields. However, due to low contrast and relatively close linear attenuation coefficients, some early small lesions are difficult to detect in time. Using the X-ray fluorescent effect of high atomic number metal elements and metal atom-containing agents that can be enriched in the lesion, the fluoroscopy signal and the fluorescent signal emitted by the metal atoms can be detected at the same time during the fluoroscopy, and the images of the two can be integrated, which can theoretically enhance the contrast between the lesion and the surrounding tissue. Based on GEANT4, this paper conducts Monte Carlo simulations to explore the feasibility and enhancement effects of three enhancement schemes: the pencil beam spot scanning method, cone-beam collimation method, and slit scanning method, and discusses the specific geometric structure and material selection.

Development and performance evaluation of large-area hybrid gamma imager (LAHGI)

We report the development of a gamma-ray imaging device, named Large-Area Hybrid Gamma Imager (LAHGI), featuring high imaging sensitivity and good imaging resolution over a broad energy range. A hybrid collimation method, which combines mechanical and electronic collimation, is employed for a stable imaging performance based on large-area scintillation detectors for high imaging sensitivity. The system comprises two monolithic position-sensitive NaI(Tl) scintillation detectors with a crystal area of 27 × 27 cm2 and a tungsten coded aperture mask with a modified uniformly redundant array (MURA) pattern. The performance of the system was evaluated under several source conditions. The system showed good imaging resolution (i.e., 6.0–8.9° FWHM) for the entire energy range of 59.5–1330 keV considered in the present study. It also showed very high imaging sensitivity, successfully imaging a 253 μCi 137Cs source located 15 m away in 1 min; this performance is notable considering that the dose rate at the front surface of the system, due to the existence of the 137Cs source, was only 0.003 μSv/h, which corresponds to ∼3% of the background level.

Comparative Analysis of Change between Ellipsoidal Height Differences and Equivalent Orthometric Height Difference

Height is an important component in the determination of the position of a point. The study aimed at performing a comparative analysis of change between ellipsoidal height differences and the equivalent orthometric height difference of points. A hi-target Differential Global Positioning System (DGPS) was used to acquire GPS data with an occupation period of thirty (30) minutes on each point, which were processed using Hi-target Geomatics Office (HGO) software to obtain the ellipsoidal heights. An automatic level instrument was used to acquire leveling data, which were processed using the height of collimation method to obtain the orthometric heights. A total of fifty (50) points were occupied as common points for both the GPS and levelling observations at 20-meter intervals. The accuracy of the height difference was determined using standard deviation with the ellipsoidal height difference as 53.59cm and the orthometric height as 53.07cm respectively. A Root Mean Square Error value of 0.0621m was obtained as the accuracy of the change between the two height differences. Statistical analysis using the independent-sample Z test was used to analyze the data at a 5% significant level. The result shows no significant difference in the performance of the two height systems. It is worthy to note that GPS and spirit levelling height differences can be used interchangeably for any heighting in short distances for surveying and engineering applications.

Study of a collimation method as a nondestructive diagnostic diagnostic technique by PGNAA for salt distribution in concrete structures at RANS

To meet strong demand for realizing an effective tool to diagnose salt distribution in concrete infrastructures, we have started a development of a new technique using a prompt gamma neutron activation analysis (PGNAA) at the RIKEN accelerator-driven compact neutron source (RANS). So far, by applying PGNAA we have experimentally confirmed that neutrons from RANS can detect small enough amounts of chlorine within the marginal concentration of around 1.2 kg/m3 to involve steel corrosion. In this study, we have proposed two methods to derive the salt depth profile which is critical information of steel corrosion start. The first one utilizes a difference in the intensity ratio of two different γ-ray energies of interest, which is depending on the depth where the neutron capture reaction arises inside the concrete. The second is called the collimator method that measure γ-rays coming through a collimator around detector. Detection of γ-ray associated with 35Cl coming from the assembly of concrete has been also simulated with conditions of neutrons from RANS and a collimator. The feasibility of the method was discussed.

Collimation method studies for next-generation hadron colliders

In order to handle extremely-high stored energy in future proton-proton colliders, an extremely high-efficiency collimation system is required for safe operation. At LHC, the major limiting locations in terms of particle losses on superconducting (SC) magnets are the dispersion suppressors (DS) downstream of the transverse collimation insertion. These losses are due to the protons experiencing single diffractive interactions in the primary collimators. How to solve this problem is very important for future proton-proton colliders, such as the FCC-hh and SPPC. In this article, a novel method is proposed, which arranges both the transverse and momentum collimation in the same long straight section. In this way, the momentum collimation system can clean those particles related to the single diffractive effect. The effectiveness of the method has been confirmed by multi-particle simulations. In addition, SC quadrupoles with special designs such as enlarged aperture and good shielding are adopted to enhance the phase advance in the transverse collimation section, so that tertiary collimators can be arranged to clean off the tertiary halo which emerges from the secondary collimators and improve the collimation efficiency. With one more collimation stage in the transverse collimation, the beam losses in both the momentum collimation section and the experimental regions can be largely reduced. Multi-particle simulation results with the MERLIN code confirm the effectiveness of the collimation method. At last, we provide a protection scheme of the SC magnets in the collimation section. The FLUKA simulations show that by adding some special protective collimators in front of the magnets, the maximum power deposition in the SC coils is reduced dramatically, which is proven to be valid for protecting the SC magnets from quenching.

КОМБИНИРОВАННЫЙ МЕТОД ЦЕНТРИРОВАНИЯ ЛИНЗ ИЗ НЕПРОЗРАЧНЫХ В ВИДИМОЙ ОБЛАСТИ СПЕКТРА МАТЕРИАЛОВ

The mixed method of optical components which is nontransparent in visual spectral range during frame processing is discussed. Theproposed method requires the following: one lens surface is positioned under mechanical control method and another lens surface is positioned under optical control method (collimation method) in floating holder. The article presents the comparison of the mixed method with centration method by two Zabelin tubes, and relative decentering measurements of lenses in frames centered by means of these methods.

基于激光跟踪仪的快速镜面准直与姿态测量方法

基于激光跟踪仪的快速镜面准直与姿态测量方法

Dynamic electronic collimation method for 3-D catheter tracking on a scanning-beam digital x-ray system.

Scanning-beam digital x-ray (SBDX) is an inverse geometry x-ray fluoroscopy system capable of tomosynthesis-based 3-D catheter tracking. This work proposes a method of dose-reduced 3-D catheter tracking using dynamic electronic collimation (DEC) of the SBDX scanning x-ray tube. This is achieved through the selective deactivation of focal spot positions not needed for the catheter tracking task. The technique was retrospectively evaluated with SBDX detector data recorded during a phantom study. DEC imaging of a catheter tip at isocenter required 340 active focal spots per frame versus 4473 spots in full field-of-view (FOV) mode. The dose-area product (DAP) and peak skin dose (PSD) for DEC versus full FOV scanning were calculated using an SBDX Monte Carlo simulation code. The average DAP was reduced to 7.8% of the full FOV value, consistent with the relative number of active focal spots (7.6%). For image sequences with a moving catheter, PSD was 33.6% to 34.8% of the full FOV value. The root-mean-squared-deviation between DEC-based 3-D tracking coordinates and full FOV 3-D tracking coordinates was less than 0.1mm. The 3-D distance between the tracked tip and the sheath centerline averaged 0.75mm. DEC is a feasible method for dose reduction during SBDX 3-D catheter tracking.

Sidelobe Suppression and Beam Collimation in the Generation of Vortex Electromagnetic Waves for Radar Imaging

For the electromagnetic (EM) vortex imaging purposes, the sidelobe suppression and the beam collimation method in the generation of orbital angular momentum (OAM) beams is proposed. Based on the concentric ring array, the objective function for the generic algorithm is defined to calculate the signal amplitude for each ring. Comprehensive simulations are conducted to validate the effectiveness of the proposed method. Results show that the main lobes of the radiation pattern of different OAM modes are collimated in the same direction and the sidelobes are all lower than –20 dB. Furthermore, the imaging model of the concentric-ring array is established, and the target image is obtained through numerical simulations. The work can advance the development of the EM vortex imaging technique and novel radar detection technology as well.

Measurements and analysis of a high-brightness electron beam collimated in a magnetic bunch compressor

A collimator located in a magnetic bunch compressor of a linear accelerator driven x-ray free electron laser has many potential applications, such as the removal of horns in the current distribution, the generation of ultrashort beams, and as a diagnostic of the beam slice emittance. Collective effects, however, are a major concern in applying the technique. Systematic measurements of emittance and analysis were performed using a collimator in the first bunch compressor of the Linac Coherent Light Source (LCLS). In the nominal, undercompressed configuration using the collimator we find that the $y$ emittance (nonbending plane) is not increased, and the $x$ emittance (in the bending plane) is increased by about 25%, in comparison to the injector emittance. From the analysis we conclude that the parasitic effects associated with this method are dominated by coherent synchrotron radiation (CSR), which causes a ``systematic error'' for measuring slice emittance at the bending plane using the collimation method. In general, we find good agreement between the measurements and simulations including CSR. However, for overcompressed beams at smaller collimator gaps, an extra emittance increase is found that does not agree with 1D simulations and is not understood.

Gamma emission tomosynthesis based on an automated slant hole collimation system

The imaging capabilities of radioisotope molecular imaging systems are limited by their ring geometry and by the object-to-detector distance, which impairs spatial resolution, efficiency and image quality. These detection capabilities could be enhanced by performing acquisitions with dedicated gamma cameras placed in close proximity to the object that has to be examined. The main aim of this work is to develop a compact camera suitable for detecting small and low-contrast lesions, with a higher detection efficiency than conventional SPECT, through a gamma emission tomosynthesis method. In this contribution a prototype of a new automated slant hole collimator, coupled to a small Field of View (FoV) gamma camera, is presented. The proposed device is able to acquire planar projection images at different angles without rotating around the patient body; these projection images are then three-dimensional reconstructed. Therefore, in order to perform the volumetric reconstruction of the studied object, the traditional Back Projection (BP) reconstruction is compared with the Shift And Add (SAA) method. In order to verify the effectiveness of the technique and to test the image reconstruction algorithms, a Monte Carlo simulation, based on the GEANT4 code, was implemented. The method was also validated by a set of experimental measurements. The discussed device is designed to work in patient proximity for detecting lesions placed at a distances ranged from 0 to 8 cm, thus allowing few millimeters planar resolutions and sagittal resolution of about 2 cm. The new collimation method implies high-resolution capabilities demonstrated by reconstructing the projection images through the BP and the SAA methods. The latter is simpler than BP and produces comparable spatial resolutions with respect to the traditional tomographic method, while preserving the image counts.

Development of a Compton camera for safeguards applications in a pyroprocessing facility

The Compton camera has a potential to be used for localizing nuclear materials in a large pyroprocessing facility due to its unique Compton kinematics-based electronic collimation method. Our RD however, the monolithic types, require a stochastic-method-based position-estimating algorithm for improving the position resolution.

Sci—Thur PM: Planning & Delivery — 03: Automated delivery and quality assurance of a modulated electron radiation therapy plan

Modulated electron radiation therapy (MERT) offers the potential to improve healthy tissue sparing through increased dose conformity. Challenges remain, however, in accurate beamlet dose calculation, plan optimization, collimation method and delivery accuracy. In this work, we investigate the accuracy and efficiency of an end‐to‐end MERT plan and automated‐delivery workflow for the electron boost portion of a previously treated whole breast irradiation case. Dose calculations were performed using Monte Carlo methods and beam weights were determined using a research‐based treatment planning system capable of inverse optimization. The plan was delivered to radiochromic film placed in a water equivalent phantom for verification, using an automated motorized tertiary collimator. The automated delivery, which covered 4 electron energies, 196 subfields and 6183 total MU was completed in 25.8 minutes, including 6.2 minutes of beam‐on time with the remainder of the delivery time spent on collimator leaf motion and the automated interfacing with the accelerator in service mode. The delivery time could be reduced by 5.3 minutes with minor electron collimator modifications and the beam‐on time could be reduced by and estimated factor of 2–3 through redesign of the scattering foils. Comparison of the planned and delivered film dose gave 3%/3 mm gamma pass rates of 62.1, 99.8, 97.8, 98.3, and 98.7 percent for the 9, 12, 16, 20 MeV, and combined energy deliveries respectively. Good results were also seen in the delivery verification performed with a MapCHECK 2 device. The results showed that accurate and efficient MERT delivery is possible with current technologies.

Delivery validation of an automated modulated electron radiotherapy plan.

Modulated electron radiation therapy (MERT) represents an active area of interest that offers the potential to improve healthy tissue sparing in treatment of certain cancer cases. Challenges remain however in accurate beamlet dose calculation, plan optimization, collimation method, and delivery accuracy. In this work, the authors investigate the accuracy and efficiency of an end-to-end MERT plan and automated delivery method. Treatment planning was initiated on a previously treated whole breast irradiation case including an electron boost. All dose calculations were performed using Monte Carlo methods and beam weights were determined using a research-based treatment planning system capable of inverse optimization. The plan was delivered to radiochromic film placed in a water equivalent phantom for verification, using an automated motorized tertiary collimator. The automated delivery, which covered four electron energies, 196 subfields, and 6183 total MU was completed in 25.8 min, including 6.2 min of beam-on time. The remainder of the delivery time was spent on collimator leaf motion and the automated interfacing with the accelerator in service mode. Comparison of the planned and delivered film dose gave 3%/3mm gamma pass rates of 62.1%, 99.8%, 97.8%, 98.3%, and 98.7% for the 9, 12, 16, and 20 MeV, and combined energy deliveries, respectively. Delivery was also performed with a MapCHECK device and resulted in 3%/3 mm gamma pass rates of 88.8%, 86.1%, 89.4%, and 94.8% for the 9, 12, 16, and 20 MeV energies, respectively. Results of the authors' study showed that an accurate delivery utilizing an add-on tertiary electron collimator is possible using Monte Carlo calculated plans and inverse optimization, which brings MERT closer to becoming a viable option for physicians in treating superficial malignancies.