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The ultra-high dose rate (UHDR) radiation has less side effect while keep comparable tumor control effect with conventional dose rate (CONV) radiation, which was named Flash effect. Recently, the Flash effect has been reported in many animal experiments with various types of radiations, animal species and body parts. However, the underlying mechanism of Flash has still been unraveled, making difficulties for the clinical application. This review pointed out the differences between the Flash effect and the UHDR effect in vitro and proposed three key scientific questions of Flash effect based on three well-known hypotheses, i. e., oxygen depletion, peroxyl radical recombination and immune cell protection. Finally, the research progresses and challenges of Flash mechanism study are concluded in order to give a clue for further deep investigation.
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The axon initial segment (AIS) is a highly specialized axonal compartment where the action potential is initiated. The heterogeneity of AISs has been suggested to occur between interneurons and pyramidal neurons (PyNs), which likely contributes to their unique spiking properties. However, whether the various characteristics of AISs can be linked to specific PyN subtypes remains unknown. Here, we report that in the prelimbic cortex (PL) of the mouse, two types of PyNs with axon projections either to the contralateral PL or to the ipsilateral basal lateral amygdala, possess distinct AIS properties reflected by morphology, ion channel expression, action potential initiation, and axo-axonic synaptic inputs from chandelier cells. Furthermore, projection-specific AIS diversity is more prominent in the superficial layer than in the deep layer. Thus, our study reveals the cortical layer- and axon projection-specific heterogeneity of PyN AISs, which may endow the spiking of various PyN types with exquisite modulation.
Sujets)
Souris , Animaux , Segment initial de l'axone , Synapses/physiologie , Cellules pyramidales/physiologie , Cortex cérébral , Axones/physiologieRésumé
Objective:To explore the feasibility of synthetic diamond detector in use for Flash radiation dosimetry by designing a diamond dosimeter and conducting a series of dosimetric characteristic tests.Methods:A diamond detector system prototype with real-time current output was developed using a CIVIDEC? B1HV diamond sensor and designing a large dynamic range current measurement circuit based on the pre-integration method. The dose (dose-rate) response linearity was tested under irradiation from both electron beam and X ray ultra-high dose rate. Dose (dose-rate) calibration was performed against a medical accelerator to gain the charge-dose transfer coefficient.Results:Good linear correlation ( R2 = 0.99) between detector output charge and reference dose per pulse was shown under electron beam irradiation of 0.08-0.50 Gy/pulse. Good linearity ( R2 = 0.99) is also shown under irradiation from electron beam with ultra-high dose rate (400 Gy/s) and conventional dose rate (0.5 Gy/s). Strictly linear correlation ( R2 = 1) was shown between detector output integrated charge and reference dose under X ray irradiation at ultra-high average dose rate (75.5 Gy/s) and conventional average dose rate (0.5 Gy/s). The charge-dose and current-dose rate conversion factors for practical use were 0.751 7 μC/Gy and 0.753 5 μA·Gy·s -1, respectively. Conclusions:Considerable linearity of the diamond detector dose responses were shown under irradiation both from electron beam and X-ray beam, which could provide a relatively rapid and accurate dosimetry for Flash preclinical experiments. Furthermore, diamond detectors have great potential in the quality assurance for Flash radiotherapy.
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Objective:To describe the distribution of volumetric breast density(VBD) in different ages of Chinese women based on X-ray mammograms.Methods:Based on mammographic images of 1 140 patients from January 2010 to December 2016 in a hospital in Beijing, the VBD of women was assessed by Volpara 1.5.1 and graded according to breast imaging reporting and data system published by American College of Radiology. The patients were divided into two groups according to the median age, and the two independent samples t-test was used to compare them. The patients were also divided into four groups according to age ( <40 years, 40-49 years, 50-59 years, ≥ 60 years), and the breast thickness, breast volume, glandular volume, and VBD were compared using a One-way ANOVA analysis. Results:The median age was 50 years. The compressed breast thickness and breast volume in patients over 50 years were significantly higher than those in patients below 50 years ( t= -8.99, -7.92, P<0.001), while glandular volume and VBD were significantly lower than those below 50 years ( t= 8.11, 18.49, P<0.001). The compressed breast thickness, breast volume, glandular volume, and VBD were statistically significant different among four groups ( F=27.10, 22.34, 25.70, 122.03, P<0.001). Patients over 60 years had the lowest VBD ( t=-12.56, -15.27, -4.57, P<0.001). VBD was negatively correlated with ages ( r=0.47, P<0.001). Conclusions:The compressed breast thickness and breast volume increased with ages, while the glandular volume and VBD decreased with ages.
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Objective:The Chinese pediatric mesh-type reference phantoms were developed and applied in the dose assessment of X-ray radiography.Methods:The 5- and 10-year-old Chinese pediatric mesh-type reference phantoms were developed based on the CT data. Based on the phantoms, the Monte Carlo method was applied to simulate the X-ray radiography to calculate the organ dose conversion coefficient and the effective dose conversion coefficient in different radiography conditions.Results:The 5- and 10-year-old Chinese pediatric mesh-type reference phantoms were developed, and the physical parameters were consistent with the national standard. The differences of the organ mass between the established phantoms and reference data were within 2%. The database of the pediatric chest posteroanterior projection and abdominal anteroposterior projection, tube voltage 60-90 kVp, total filtration 2.5~4 mmAl were simulated, and the difference between the effective dose conversion factor and the literature result was within 3%.Conclusions:The established Chinese pediatric mesh-type reference phantoms can be applied in the studies of radiation protection and clinical medicine and their result can provide an important reference for the dose assessment of the pediatric X-ray radiography.
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This study aimed to investigate the method of conserving the mice skin for long time in vitro,and forty clean male KM mice of 8-week old were divided into two groups by random digit table,namely vitrified skin transplantation group(n =30) and fresh skin transplantation group(n =10) .The skin was vitrified quickly with freezing solution EFS40 by the two-step method,and then was thawed with 0.5 mol/L glucose,which was followed by self-transplanted.The vitrified skin transplantation group was self-transplanted after the skin was vitrified for 2 weeks.A piece of skin which was smaller than the vitrified one was cut off on the other side of the spine,and the thawed skin were laid smoothly to coincide with the edge of the cut skin which was sutured then.In fresh skin transplantation group,fresh skins were prepared to put in Dulbecco phosphate-buffered saline for 15 minutes and then be transplanted to original position.The outcomes of transplantation were valuated on day 14 and day 28 after transplantation.And the results indicated that the survival rate of the fresh skin transplantation group was 100%(10/10) .The survival rate of the vitrified skin transplantation group was 77%(23/30) on day 14 and 70%(21/30) on day 28,respectively.But the surfaces of the mice skin and part of the hair follicle cells were damaged during vitrification.However,the method of vitrifying the mice skin quickly in this paper may be used to conserve the skin in vitro.