Objective To determine the optimal electron beam energy at different field size through a Monte Carlo-based simulation of the therapy head of Varian X 6 MV linear accelerator so as to study the influence of radial intensity on depth dose.Methods Firstly,keeping the radial intensity unchanged for the field of interest while changing electron beam energy,compassion was carried out of calculated percentage depth doses between measured values.Thus,the optimal energy was identified for this field size.Then,the obtained energy was set the optimal value to study the radial intensity influence on the depth doses.Results The optimal electron energy for 4 cm ×4 cm,10 cm × 10 cm,20 cm × 20 cm and 30 cm × 30 cm field sizes was 5.9,6.0,6.3 and 6.4 MeV respectively.Changes in radial intensities resulted in negligible changes in percentage depth doses for4 cm ×4-cm and 10 cm × 10 cm fields,but led to observable discrepancy for 20 cm × 20 cm and 30 cm × 30 cm fields.Conclusions The optimal electron energies for different field sizes are slightly different.Change in radial intensity distribution has significant influence on the depth dose for large field.To improve simulation accuracy,the field size needs to be taken into consideration in determining the electron beam energy and radial intensity distribution.

Objective:To explore the application value of the method of judging the density of small shadows in the lung area by using CT and CT reference films for pneumoconiosis.Methods:The chest imaging data of 244 employees of a large copper company in Tongling City, Anhui Province who underwent occupational physical examination at Tongling Municipal Hospital in Anhui Province from January 2016 to December 2019 were retrospectively analyzed. Totally 244 cases underwent chest CT scan and chest DR radiography at the same time. The shape and size of the small shadows (the size of the circular and quasi-circular nodules in the lung area were represented by p, q, r, and the size of the irregular small shadows were represented by s, t, u), the overall density, the density of small shadows in each lung area, the large shadows, and the diagnosis stage were observed and compared. The small shadow density of each lung area was judged by the method of judging the small shadow density of CT lung area and the reference film, and other observation indicators were judged according to GBZ70-2015 Diagnosis of Occupational Pneumoconiosis. Results:There was a significant difference between CT and DR in judging s-shaped small shadows and no small shadows ( P<0.05), and there was no statistically significant difference in judging p, q, r, t, and u-shaped small shadows ( P>0.05). CT and DR had medium to high consistency in the judgment of the overall density of small shadows (Kappa=0.692, P=0.001), and the diagnostic coincidence rate was 82.38% (201/244). There was moderate to high agreement between CT and DR in the density of small shadows shown in the right upper, right lower, left upper, left middle, and left lower lung regions (Kappa ranged from 0.40 to 0.75, P<0.05), and the consistency in the right middle lung region was poor (Kappa=0.381, P=0.001). Eleven large shadows were detected in 8 cases by DR, 31 large shadows were detected in 23 cases by CT, and 20 (8.20%) large shadows were detected more frequently by CT than DR. The agreement between CT and DR for the diagnosis and staging of silicosis was excellent (Kappa=0.843, P=0.001), and the diagnostic coincidence rate was 91.80% (224/244). Conclusion:Applying the method of determining the density of small shadows in the lung area of pneumoconiosis and reference films, combined with GBZ70-2015 Diagnosis of Occupational Pneumoconiosis, can make a more accurate diagnosis of silicosis.

Objective To compare the difference in heart rate variability (HRV)between patients with dementia with Lewy bodies(DLB)and those with Parkinson disease dementia(PDD)and to identify the influencing factors.Methods We retrospectively enrolled 30 patients with DLB(DLB group)and 41 patients with PDD(PDD group)at the outpatient and inpatient services of our hospital from January 2010 to December 2017 in this study,and further recruited 119 normal elderly individuals to serve as the control group.HRV was recorded with 24 h dynamic electrocardiogram and compared between the DLB group and the PDD group.Time domain measures including standard deviation of all normal to normal(NN)intervals(SDNN)and square root of the mean squared differences of successive N N intervals(rMSSD)and frequency domain measures including total power(TP),low frequency(LF),and high frequency(HF)were analyzed with a customized program.The levodopa equivalent dose (LED),mini-mental state examination (MMSE),Montreal Cognitive Assessment (MoCA),Hoehn-Yahr stage(H-Y stage)and the unified Parkinson's disease rating scale Ⅲ (UPDRS Ⅲ),and the Alzheimer's disease Cooperative Study-Activities of Daily Living scale(ADCS-ADL)were assessed in DLB and PDD patients to investigate the influencing factors.Results SDNN,TP,and LF in the DLB group and the PDD group were significantly lower than in the control group (F =14.154,4.742,4.897,P＜0.05).Compared with the control group,rMSSD decreased in the DLB group,but had no significant difference in the PDD group(P＞0.05).The DLB group and the PDD group did not differ in HF from the control group (P ＞ 0.05).There was no significant difference in any HRV indexes between DLB and PDD patients(P ＞0.05).Correlation analysis showed no correlation of HRV with cognitive level(MMSE,MoCA),motor disturbance degree (UPDRS Ⅲ,H-Yahr stage),daily living ability(ADCS-ADL),or dosage of anti-PD drugs (each P ＞ 0.05).Conclusions DLB and PDD patients present similar impairments in autonomic nervous system function,which are not associated with disease severity.