FLASH radiotherapy is moving from animal experiments to clinical trials. However, the research on radiation shielding of FLASH radiotherapy rooms has been still in the initial stage. This paper analyses the structural characteristics of the beam pulse of FLASH radiotherapy devices of different technical routes, and discusses the radiation shielding challenges facing the radiotherapy room from FLASH radiotherapy technology based on the current protection standards for the radiotherapy room at home and abroad. The purpose is to provide input to the research on radiation protection of FLASH radiotherapy and to promote the clinical development of FLASH radiotherapy.

FLASH irradiation (FLASH-IR) is one of the cutting-edge research directions in the field of tumor radiotherapy. Previous studies have demonstrated that FLASH-IR can effectively eradicate tumors while significantly reducing damage to normal tissues, exhibiting unique biological effects characterized by high efficiency and low toxicity. Monte Carlo simulation at the microscopic scale is a critical method for studying radiobiological effects and has been widely applied in conventional radiotherapy research. In recent years, its application in microscopic reaction analysis and mechanistic exploration of FLASH-IR has grown rapidly. This article systematically reviews the latest advances and key challenges in microscopic Monte Carlo simulation studies of FLASH-IR, aiming to provide theoretical insights and method ological guidance for future research.

FLASH radiotherapy is moving from animal experiments to clinical trials. However, the research on radiation shielding of FLASH radiotherapy rooms has been still in the initial stage. This paper analyses the structural characteristics of the beam pulse of FLASH radiotherapy devices of different technical routes, and discusses the radiation shielding challenges facing the radiotherapy room from FLASH radiotherapy technology based on the current protection standards for the radiotherapy room at home and abroad. The purpose is to provide input to the research on radiation protection of FLASH radiotherapy and to promote the clinical development of FLASH radiotherapy.

FLASH irradiation (FLASH-IR) is one of the cutting-edge research directions in the field of tumor radiotherapy. Previous studies have demonstrated that FLASH-IR can effectively eradicate tumors while significantly reducing damage to normal tissues, exhibiting unique biological effects characterized by high efficiency and low toxicity. Monte Carlo simulation at the microscopic scale is a critical method for studying radiobiological effects and has been widely applied in conventional radiotherapy research. In recent years, its application in microscopic reaction analysis and mechanistic exploration of FLASH-IR has grown rapidly. This article systematically reviews the latest advances and key challenges in microscopic Monte Carlo simulation studies of FLASH-IR, aiming to provide theoretical insights and method ological guidance for future research.

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.

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.

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.
Mice ; Animals ; Axon Initial Segment ; Synapses/physiology* ; Pyramidal Cells/physiology* ; Cerebral Cortex ; Axons/physiology*

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.

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.

Objective: Several COVID-19 patients have overlapping comorbidities. The independent role of each component contributing to the risk of COVID-19 is unknown, and how some non-cardiometabolic comorbidities affect the risk of COVID-19 remains unclear. Methods: A retrospective follow-up design was adopted. A total of 1,160 laboratory-confirmed patients were enrolled from nine provinces in China. Data on comorbidities were obtained from the patients' medical records. Multivariable logistic regression models were used to estimate the odds ratio ( Results: Overall, 158 (13.6%) patients were diagnosed with severe illness and 32 (2.7%) had unfavorable outcomes. Hypertension (2.87, 1.30-6.32), type 2 diabetes (T2DM) (3.57, 2.32-5.49), cardiovascular disease (CVD) (3.78, 1.81-7.89), fatty liver disease (7.53, 1.96-28.96), hyperlipidemia (2.15, 1.26-3.67), other lung diseases (6.00, 3.01-11.96), and electrolyte imbalance (10.40, 3.00-26.10) were independently linked to increased odds of being severely ill. T2DM (6.07, 2.89-12.75), CVD (8.47, 6.03-11.89), and electrolyte imbalance (19.44, 11.47-32.96) were also strong predictors of unfavorable outcomes. Women with comorbidities were more likely to have severe disease on admission (5.46, 3.25-9.19), while men with comorbidities were more likely to have unfavorable treatment outcomes (6.58, 1.46-29.64) within two weeks. Conclusion Besides hypertension, diabetes, and CVD, fatty liver disease, hyperlipidemia, other lung diseases, and electrolyte imbalance were independent risk factors for COVID-19 severity and poor treatment outcome. Women with comorbidities were more likely to have severe disease, while men with comorbidities were more likely to have unfavorable treatment outcomes.
Adult ; Aged ; COVID-19/virology* ; China/epidemiology* ; Comorbidity ; Female ; Humans ; Male ; Middle Aged ; Retrospective Studies ; Severity of Illness Index ; Treatment Outcome