Subjects: Nuclear Science and Technology >> Radiation Physics and Technology submitted time 2024-05-30
Abstract： Cone-beam computed tomography (CBCT) is mostly used for position verification during the treatment pro#2;
cess. However, severe image artifacts in CBCT hinder its direct use in dose calculation and adaptive radiation
therapy re-planning for proton therapy. In this study, an improved U-Net neural network named CBAM-U-Net
was proposed for CBCT noise reduction in proton therapy, which is a CBCT denoised U-Net network with con#2;
volutional block attention modules. The datasets contained 20 groups of head and neck images. The CT images
were registered to CBCT images as ground truth. The original CBCT denoised U-Net network, sCTU-Net, was
trained for model performance comparison. The synthetic CT(SCT) images generated by CBAM-U-Net and the
original sCTU-Net are called CBAM-SCT and U-Net-SCT images, respectively. The HU accuracies of the CT,
CBCT, and SCT images were compared using four metrics: mean absolute error (MAE), root mean square error
(RMSE), peak signal-to-noise ratio (PSNR), and structure similarity index measure (SSIM). The mean values of
the MAE, RMSE, PSNR, and SSIM of CBAM-SCT images were 23.80 HU, 64.63 HU, 52.27 dB, and 0.9919,
respectively, which were superior to those of the U-Net-SCT images. To evaluate dosimetric accuracy, the range
accuracy was compared for a single-energy proton beam. The γ-index pass rates of a 4 cm × 4 cm scanned
field and simple plan were calculated to compare the effects of the noise reduction capabilities of the original
U-Net and CBAM-U-Net on the dose calculation results. CBAM-U-Net reduced noise more effectively than
sCTU-Net, particularly in high-density tissues. We proposed a CBAM-U-Net model for CBCT noise reduction
in proton therapy. Owing to the excellent noise reduction capabilities of CBAM-U-Net, the proposed model
provided relatively explicit information regarding patient tissues. Moreover, it can be used in dose calculation
and adaptive treatment planning in the future.
Subjects: Nuclear Science and Technology >> Radiation Physics and Technology submitted time 2024-04-25
Abstract： A Laue microdiffraction beamline (BL03HB) was constructed at the Shanghai Synchrotron Radiation Facility (SSRF). This beamline features two consecutive focusing points in two different sectors within its end station, the first dedicated to protein crystallography and the other tailored to materials science applications. Based on a superbend dipole magnet with a magnetic field of 2.29 T, a two-stage focusing design was implemented with two sets of Kirkpatrick–Baez mirrors to achieve a micro white beam as small as 4.2×4.3 µm 2 at the first sector and 0.9×1.3 µm 2 at the second sector in the standard beamline operation mode at SSRF. The X-ray microbeam in the two sectors can be easily switched between monochromatic and white beams by moving a four-bounce monochromator in or out of the light path, respectively. In the protein crystallography sector, white-beam Laue microdiffraction was demonstrated to successfully determine the structure of protein crystals from only a few images of diffraction data collected by a Pilatus 2M area detector. In the materials science sector, the white-beam Laue diffraction was collected in a reflection geometry using another Pilatus 2M area detector, which could map the microstructural distribution on the sample surface by scanning the samples. In general, the BL03HB beamline promotes the application of Laue microdiffraction in both protein crystallography and materials science. This paper presents a comprehensive overview of the BL03HB beamline, end station, and the first commission results.
Subjects: Physics >> Nuclear Physics submitted time 2024-03-19
Abstract： The exploration of exotic shapes and properties of atomic nuclei, e.g., α cluster and toroidal shape, is a
fascinating field in nuclear physics. To study the decay of these nuclei, a novel detector aimed at detecting
multiple alpha-particle events was designed and constructed. The detector comprises two layers of double-sided
silicon strip detectors (DSSD) and a cesium iodide scintillator array coupled with silicon photomultipliers array
as light sensors, which has the advantages of their small size, fast response, and large dynamic range. DSSDs
couple with cesium iodide crystal arrays are used to distinguish multiple alpha hits. The detector array has a
compact and integrated design that can be adapted to different experimental conditions. The detector array was
simulated using Geant4, and the excitation energy spectra of some alpha-clustering nuclei were reconstructed
to demonstrate the performance. The simulation results show that the detector array has excellent angular
and energy resolutions, enabling effective reconstruction of the nuclear excited state by multiple alpha particle
events. This detector offers a new and powerful tool for nuclear physics experiments and has the potential to
discover interesting physical phenomena related to exotic nuclear structures and their decay mechanisms
Subjects: Physics >> Nuclear Physics submitted time 2024-03-19
Abstract： In recent years, the gap between the supply and demand of medical radioisotopes has increased, necessitating new methods for producing medical radioisotopes. Photonuclear reactions based on gamma sources have unique advantages in terms of producing high specific activity and innovative medical radioisotopes. However, the lack of experimental data on reaction cross sections for photonuclear reactions of medical radioisotopes of interest has severely limited the development and production of photonuclear transmutation medical radioisotopes. In this study, the entire process of the generation, decay, and measurement of medical radioisotopes was simulated using online gamma activation and offline gamma measurements combined with a shielding gammaray spectrometer. Based on a quasi-monochromatic gamma beam from the Shanghai Laser Electron Gamma Source (SLEGS), the feasibility of the measurement of production cross section for surveyed medical isotopes was simulated, and specific solutions for measuring medical radioisotopes with low production cross sections were provided. The feasibility of this method for high precision measurements of the reaction cross section of medical radioisotopes was demonstrated.
Subjects: Nuclear Science and Technology >> Particle Accelerator submitted time 2023-08-21
Abstract： The purpose of this study was to design a rapid cycling synchrotron, making it capable of proton beam ultra-high dose rate irradiation, inspired by laser accelerators. The design had to be cheap and simple. We consider our design from six aspects: the lattice, injection, extraction, space charge effects, eddy current effects and energy switching. Efficiency and particle quantity must be addressed when injected. The space charge effects at the injection could affect particles’ number. The eddy current effects in the vacuum chambers would affect the magnetic field itself and generate heat, all of which need to be taken into account. Fast extraction can obtain 1010 protons/pulse, equal to instantaneous dose rate up to 107 Gy/s in a very short time, while changing various extraction energies rapidly and easily to various deposition depths. In the further research we expect to combine a delivery system with this accelerator to realize the FLASH irradiation.
Peer Review Status:
Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2023-08-11
Abstract： Multi-objective evolutionary algorithms (MOEAs) are typically used to optimize two or three objectives in the accelerator field and perform well. However, the performance of these algorithms may severely deteriorate when the optimization objectives for an accelerator [A1] are equal to or greater than four. Recently, many-objective evolutionary algorithms (MaOEAs) that can solve problems with four or more optimization objectives have received extensive attention. In this study, two diffraction-limited storage ring (DLSR) lattices of the ESRF-EBS [A2] type with different energies were designed and optimized using three MaOEAs and a widely used MOEA. The initial population[A3] was found to have a significant impact on the performance of the algorithms and was carefully studied. The performances of the four algorithms were compared, and the results demonstrated that the grid-based evolutionary algorithm (GrEA) had the best performance. MaOEAs were applied in many-objective optimization of DLSR lattices for the first time, and lattices with natural emittances of 116 pm∙rad and 23 pm∙rad were obtained at energies of 2 GeV and 6 GeV, respectively, both with reasonable dynamic aperture and local momentum aperture (LMA). This work provides a valuable reference for future multi-objective optimization of DLSRs.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2023-06-20
Abstract：
Subjects: Physics >> Nuclear Physics submitted time 2022-06-13
Abstract：Shanghai Laser Electron Gamma Source (SLEGS) is a powerful gamma source to provide MeV gamma-ray beams for nuclear science and technology. It is developed as one of the sixteenbeamline stations in Phase II Project of the Shanghai Synchrotron Radiation Facility (SSRF). Theslant-scattering mode is for the first time systematically employed in the laser Compton scattering (LCS) at SLEGS to produce energy-tunable quasi-monoenergetic gamma-ray beams. SLEGS officially completed its commissioning from July to December 2021. Gamma-rays in energy range of 0.25 - 21.7 MeV with the flux of 2.1 104 - 1.2 107 photons/s and the energy spread of 2 15 % are produced during the test. This paper reports results of the commissioning of the SLEGS beamline.
Peer Review Status:Awaiting Review
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