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中国生物医学工程学会
北京玛格泰克科技发展有限公司
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2021 Vol. 30, No. 2
Published: 2021-06-30
Research papers
Research papers
47
The Characteristic of Dose Equivalent Rates of Photon and Neutron Outside the Treatment Room under High-energy Electron Mode of Linac
ZHANG Shu-xu, YANG Lu, LIN Sheng-qu, ZHANG Quan-bin, YANG Hao-xian, ZHANG Guo-qian, CHEN Jin-hui, LUO Song-gui, ZHOU Pi-xiao
Objective:
The study aimed to explore the characteristic of dose equivalent rates (DERs) of photon and neutron outside the treatment room under high-energy electron mode (dose rate 1000 MU/min) of linac and to evaluate the effectiveness of treatment room protection.
Methods:
A 451P pressurized ion chamber and a thermo neutron detector were used to measure the DERs of the photon and neutron at selected points. The effects of field size, applicator size, applicator, anthropomorphic phantom (CDP) and lead block on DER were investigated respectively.
Results:
The DERs of a photon at the center of shielding door (point A), control console (point B), primary shielding walls (point C, D) and roof of treatment room (point E) increased with increasing electron energy, but decreased with the increasing field size. The DERs of a photons at points A and B are smaller than 2.5 μSv/h for all scenarios, while those at point D greater than 2.5 μSv/h when irradiated by 18-22 MeV electron. In addition, CDP may change the DERs of a photon at points C and D about 5% to 30%. On the other hand, the DERs of neutron increase with increasing electron energy but decrease with the increase of field size and applicator size, however, the lead block and the applicator itself will change the DERs of leak neutron at point A, but its amplitude is less than 0.5 μSv/h. The maximum DER of neutron at point A is 6.18 μSv/h irradiated by 22 MeV electron. For other scenarios, they are all in the range of national standards limits.
Conclusion:
The DERs of a photon and neutron outside the treatment room mainly depend on the energy, field size and irradiation direction of the electron beam. If high-energy 18 MeV and 22 MeV electron beams will be used, the primary shielding walls and shielding doors need reconstructing or increasing thickness.
2021 Vol. 30 (2): 47-57 [
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192
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58
Silicon-alloyed Isotropic Pyrolytic Carbon Prepared by Steady-state Fluidized Bed Chemical Vapor Deposition
ZHANG Jian-hui, LIU Gang, ZHENG Yan-zhen
Silicon-alloyed isotropic pyrolytic carbon (Si-IPyC) was prepared by steady-state fluidized bed chemical vapor deposition (SFBCVD). The effects of deposition temperature and propane concentration on the microstructure and deposition process of Si-IPyC were investigated using X-ray diffraction (XRD), X-ray energy dispersive spectrometer (EDS) and scanning electron microscope (SEM). The results show that the Si-IPyC with different silicon content is composed of both spherical granular and laminar structures, and silicon element is uniformly dispersed in pyrolytic carbon in the form of
β
-SiC. The deposition temperature and propane concentration have a great influence on the microstructure of Si-IPyC, with the increase of deposition temperature or propane concentration, the laminar structure in Si-IPyC decreases gradually, spherical granular morphology becomes increasingly obvious and the density decreases with the deposition model changing from surficial growth mechanism to gaseous nucleation mechanism. For getting a faster average coating rate, deposition temperature and propane concentration should not be too high.
2021 Vol. 30 (2): 58-68 [
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137
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69
A Method of Acquiring Raman Spectrum for Blood Samples with Low Cost
BAI Yang
Blood is composed of plasma and blood cells. Plasma contains many kinds of proteins, free DNA, inorganic salt, fat, sugar, hormones and other chemical components. The changes in these components can reflect the health status of the body. Raman spectroscopy as a vibrational spectroscopic technique could gain label-free, non-destructive biochemical information about blood samples. It has a huge potential as a clinical diagnostic tool. However, the drawbacks with the application of the technique include sample preparation, expensive substrates and long acquisition times. Our study aims to establish a method of acquiring Raman spectrum of blood samples with stability, accuracy and low cost. In this study, we investigated the different instrumental and sample preparation parameters to identify the best combination for acquiring spectrum from blood plasma. It could be the technological basis of the potential application of Raman spectroscopy in clinical diagnosis.
2021 Vol. 30 (2): 69-74 [
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139
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75
Glucocorticoids Inducing Vascular Repair Disorders under Hypoxia via Inhibiting Cell Migration and Autocrine/paracrine: Bioinformatical Analysis Combined with Cytological Experiment
MA Jun, YANG Pei, WANG Kun-zheng
The exact molecular and cytological mechanism of how glucocorticoids induce vascular repair disorders in glucocorticoid-induced avascular necrosis of the femoral head is still unclear. We used bioinformatical tools for data mining and detected the biological behavior of endothelial cells (ECs) under hypoxia conditions and high dose dexamethasone to reveal the mechanisms above.
Six differential expression miRNAs (DE-miRNAs) were filtered from Gene Expression Omnibus (GEO) database GSE60093 which contained ECs treated with high dose glucocorticoid and control samples. Enrichment and PPI network analyses of the DE-miRNAs target genes showed the most remarkable pathway was HIF-1 signaling pathway and high dose glucocorticoid as a negative regulator of cell differentiation, energy metabolism, migration and cytokines secretion. Glucocorticoids also reduced the activity of autocrine/paracrine via limiting ion channels and transmembrane transporter process.
In cytological experiment, HUVECs were divided into four groups: hypoxia group (H), hypoxia + dexamethasone group (HD), dexamethasone group (D), the normal group (N). Cell activity detection and Live/Dead dyeing showed cell activity and the number of live cells in Group H was higher than the other three groups at 24 h after intervention, while cell activity, number and proportion of live cells in HD group were worst. Cytoskeleton staining showed HD group met cytoskeleton form disorders. The scratch assay showed cell migration ability of Group H was strongest while cell migration ability of the HD group was worst. MIF expression in HD group showed a trend of bimodal, the peak of VEGF-A secretion lagged behind the MIF's. Expression of MIF and VEGF-A in the HD group were low. High dose dexamethasone suppressed the active response of ECs to hypoxia stimulation via directly inhibiting the expression of MIF and interdicting autocrine/paracrine mechanism. We infered that the treatment with high dose glucocorticoid would inhibit neo-angiogenesis under hypoxia followed by aggravating hypoxia/ischemia and osteonecrosis.
2021 Vol. 30 (2): 75-92 [
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