Subjects: Nuclear Science and Technology >> Radiation Protection Technology submitted time 2023-11-20
Abstract： Objective: The increasing incidence of breast cancer among Chinese women has necessitated the utilization of breast X-ray screening, which carries radiation risk. This work aims to provide a dosimetry protocol for the Chinese female population, to replace the traditional standard that utilize simplified breast models, for the accurate estimation of patients’ mean glandular dose undergoing digital breast tomosynthesis (DBT).
Approach: We have constructed the first set of Chinese female detailed breast models with their representative breast parameters. Considering the backscatter radiation and computational efficiency, we improved the combination of these models and the Chinese reference adult female whole-body voxel phantom. The image acquisition for four commercial DBT systems, which are widely employed in China, were simulated using the Monte Carlo method to obtain the normalized glandular dose coefficients of DBT (D_gN^DBT) and glandular depth dose (Dgdepz ) for different breast characteristics and X-ray spectra.
Main results: We calculated a series of D_gN^DBT for breasts with different percentage mass glandularity (5%, 25%, 50%, 75%, and 100%) and compressed breast thicknesses (2cm, 3cm, 4cm, 5cm, 6cm, 7cm), at various tube potentials (25kV, 28kV, 30kV, 32kV, 35kV, and 49kV) and target/filter combinations (W/Rh, W/Al, Mo/Mo, Rh/Rh, Rh/Ag). The parameter dependence of breast characteristics and beam conditions on D_gN^DBT of detailed breast models were investigated. The D_gN^DBT results were 14.6% - 51.0% lower than those of the traditional dosimetry standard in China. The difference in D_gN^DBT was mainly due to the decrease in the depth of the main energy deposition area caused by glandular distribution along the depth direction.
Significance: The results obtained in this work could be employed for the improvement of breast dosimetry in China, and provide more detailed information about risk assessment undergoing DBT.
Subjects: Physics >> Nuclear Physics submitted time 2023-10-23
Abstract： Monte Carlo simulations are frequently utilized in radiation dose assessments. However, many researchers find the prevailing computing platforms to be intricate. This highlights a pressing need for a specialized framework for phantom dose evaluation. To address this gap, we developed a user-friendly radiation dose assessment platform using the Monte Carlo toolkit, Geant4. The Tsinghua University Phantom Dose (THUDosePD) augments the flexibility of Monte Carlo simulations in dosimetric research. Originating from THUDose, a code with generic, functional, and application layers, THUDosePD focuses predominantly on anatomical phantom dose assessment. Additionally, it enables medical exposure simulation, intricate geometry creation, and supports both three-dimensional radiation dose analysis and phantom format transformations. The system operates on a multi-threaded parallel CPU architecture, with some modules enhanced for GPU parallel computing. Benchmark tests on the ICRP reference male illustrated the capabilities of THUDosePD in phantom dose assessment, covering the effective dose, three-dimensional dose distribution, and three-dimensional organ dose. We also conducted a voxelization conversion on the polygon mesh phantom, demonstrating the method’s efficiency and consistency. Extended applications based on THUDosePD further underline its broad adaptability. This intuitive, three-dimensional platform stands out as a valuable tool for phantom radiation dosimetry research.
Subjects: Nuclear Science and Technology >> Nuclear Science and Technology submitted time 2023-08-27
Abstract： Intensity-modulated particle therapy (IMPT) with carbon ions is comparatively susceptible to various uncertainties caused by breathing motion, including range, setup, and target positioning uncertainties. To determine relative biological effectiveness-weighted dose (RWD) distributions that are resilient to these uncertainties, the reference phase-based four-dimensional (4D) robust optimization (RP-4DRO) and each phase-based 4D robust optimization (EP-4DRO) method in carbon-ion IMPT treatment planning were evaluated and compared. Based on RWD distributions, 4DRO methods were compared with 4D conventional optimization using planning target volume (PTV) margins (PTV-based optimization) to assess the effectiveness of the robust optimization methods. Carbon-ion IMPT treatment planning was conducted in a cohort of five lung cancer patients. The results indicated that the EP-4DRO method provided better robustness (P=0.080) and improved plan quality (P=0.225) for the clinical target volume (CTV) in the individual respiratory phase when compared with the PTV-based optimization. Compared with the PTV-based optimization, the RP-4DRO method ensured the robustness (P = 0.022) of the dose distributions in the reference breathing phase, albeit with a slight sacrifice of the target coverage (P=0.450). Both 4DRO methods successfully maintained the doses delivered to the organs at risk (OARs) below tolerable levels, which were lower than the doses in the PTV-based optimization (P<0.05). Furthermore, the RP-4DRO method exhibited significantly superior performance when compared with the EP-4DRO method in enhancing overall OAR sparing in either the individual respiratory phase or reference respiratory phase (P<0.05). In general, both 4DRO methods outperformed the PTV-based optimization in terms of OAR sparing and robustness.
Peer Review Status:
Awaiting Review
Subjects: Biology >> Ecology submitted time 2023-07-06
Abstract： Both aquatic and terrestrial biodiversity information can be detected in riverine water environmental DNA (eDNA). However, the effectiveness of using riverine water eDNA to simultaneously monitor the riverine and terrestrial biodiversity information remains unidentified. Here, we proposed that the monitoring effectiveness could be approximated by the transportation effectiveness of land-to-river and upstream-to-downstream biodiversity information flows and described by three new indicators. Subsequently, we conducted a case study in a watershed on the Qinghai-Tibet Plateau. The results demonstrated that there was higher monitoring effectiveness on summer or autumn rainy days than in other seasons and weather conditions. The monitoring of the bacterial biodiversity information was more efficient than the monitoring of the eukaryotic biodiversity information. On summer rainy days, 43-76% of species information in riparian sites could be detected in adjacent riverine water eDNA samples, 92-99% of species information in riverine sites could be detected in a 1-km downstream eDNA sample, and half of dead bioinformation (the bioinformation labeling the biological material that lacked life activity and fertility) could be monitored 4-6 km downstream for eukaryotes and 13-19 km downstream for bacteria. The current study provided reference method and data for future monitoring projects design and for future monitoring results evaluation.
Subjects: Nuclear Science and Technology >> Radiation Physics and Technology submitted time 2023-05-31
Abstract： Carbon-ion radiotherapy (CIRT) offers unique physical and biological advantages over photon radiotherapy. However, some
materials and devices in the CIRT treatment room become radioactive under bombardment by therapeutic carbon-ion beams
due to nuclear reactions, thereby leading to possible radiation hazards to medical staff and additional and unwanted doses
to patients. This study assessed the level of induced radioactivity in the treatment room of the Heavy-Ion Medical Machine
(HIMM) in Wuwei. Monte Carlo simulations using PHITS were performed for a conservative case under the conditions of
maximum beam energy and intensity provided by the HIMM facility. The geometry and configuration of Treatment Room
2 of the HIMM facility in Wuwei were adopted. We evaluated the activation of air, the phantom, and the components of
the beamline, such as the primary collimator (PC), ridge filter (RF), and multileaf collimator (MLC). For air activation,
we calculated the medical staff immersion external exposure and inhalation internal exposure caused by the corresponding
radionuclides. For phantom activation, we estimated the additional dose to the patient’s family members owing to secondary
photons after treatment. In addition, the exemption or non-exemption of the component material activation was assessed.
The results showed that external radiation caused by air activation was the main source of the annual effective dose at
approximately 0.5 mSv/y. The induced radioactivity exposure to family members of a patient after CIRT was approximately
40 μSv, sufficiently lower than the public dose limit of 1 mSv/a. The induced radioactivity of the PC, RF, and MLC was all
above the exempt levels after the devices were retired, whereas the induced radioactivity of the RS and compensator could
reach the exempt levels after one patient session. Our study indicated that medical staff engaged in CIRT should stay away
from the high-dose-rate area of induced radioactivity along the beam direction, shorten the residence time in the treatment
room as much as possible, and store the activated components in isolation after the equipment is out of use. Thus, this study
provides guidance for accurately assessing the level of induced radioactivity in the treatment room for CIRT.
Subjects: Biology >> Biophysics >> Biochemistry & Molecular Biology submitted time 2016-05-15
Wu, Fan
Qi, Xin
Zhao, Hong-Yu
Wang, Zheng
Zhang, Hui
Ren, Jin-Qi
Feng, Wei
Hu, Jun-Jie
Zhang, Hong
Watanabe, Yasunori
Fujioka, Yuko
Noda, Nobuo N.
Guo, Xiang-Yang
Fang, Tian-Cheng
Wang, Peng
Shen, Yu-Xian
Abstract： Multicellular organisms have multiple homologs of the yeast ATG8 gene, but the differential roles of these homologs in autophagy during development remain largely unknown. Here we investigated structure/function relationships in the two C. elegans Atg8 homologs, LGG-1 and LGG-2. lgg-1 is essential for degradation of protein aggregates, while lgg-2 has cargo-specific and developmental-stage-specific roles in aggregate degradation. Crystallography revealed that the N-terminal tails of LGG-1 and LGG-2 adopt the closed and open form, respectively. LGG-1 and LGG-2 interact differentially with autophagy substrates and Atg proteins, many of which carry a LIR motif. LGG-1 and LGG-2 have structurally distinct substrate binding pockets that prefer different residues in the interacting LIR motif, thus influencing binding specificity. Lipidated LGG-1 and LGG-2 possess distinct membrane tethering and fusion activities, which may result from the N-terminal differences. Our study reveals the differential function of two ATG8 homologs in autophagy during C. elegans development.
Peer Review Status:Awaiting Review
Subjects: Biology >> Biophysics submitted time 2016-05-11
Li, Yan
Shah, Punit
De Marzo, Angelo M.
Chan, Daniel W.
Zhang, Hui
Van Eyk, Jennifer E.
Li, Yan
Lo, Qianqian
Van Eyk, Jennifer E.
Abstract： Glycosylation is one of the most common protein modifications. Each glycoprotein can be glycosylated at multiple glycosites, and each glycosites can be modified by different glycans. Due to this heterogeneity of glycosylation, it has proven difficult to study the structure-function relationship of specific glycans and their affected glycoproteins. Here, we report a novel method for rapid and quantitative identification of glycoproteins containing specific glycans. Lectin affinity isolations are followed by chemical immobilization of the captured glycopeptides, allowing the identification of glycoproteins containing specific glycans by subsequent mass spectrometry. The application of the method should be useful to facilitate our understanding of how changes in glycan associate with diseases, and to discover novel glycoproteins with certain glycans that could serve as biomarkers or therapeutic targets.
Peer Review Status:Awaiting Review
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