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Objective:To compare the abilities of different neural networks to generate pseudo-computed tomography (CT) images from magnetic resonance imaging (MRI) images and to explore the feasibility of pseudo-CT for clinical radiotherapy planning.Methods:A total of 29 brain cancer patients with planning CT and diagnostic MRI were selected. 23 of these patients were used for training neural networks and 6 for testing pseudo-CT images. Cycle-consistent generative adversarial network (cycleGAN), contrastive learning for unpaired image-to-image translation (CUT), and improved network denseCUT proposed in this study were applied to generate pseudo-CT images from MRI images. The pseudo-CT images were imported into a clinical treatment planning system to verify the feasibility of applying this method to radiotherapy planning.Results:The comparison between the generated pseudo-CT images and real CT images showed that the mean absolute errors were (72.0±6.9), (72.5±8.0), and (64.6±7.3) HU for the cycleGAN, CUT, and denseCUT, respectively. Meanwhile, the structure similarity indices were 0.91±0.01, 0.91±0.01, and 0.93±0.01, respectively. The peak signal-to-noise ratios were (28.5±0.7), (28.5±0.7), and (29.5±0.7) dB, respectively. The 2%/2 mm γ passing rates were 98.05%, 97.92%, and 98.31% for the cycleGAN, CUT, and denseCUT, respectively.Conclusions:DenseCUT can generate more accurate pseudo-CT images and the pseudo-CT can meet the demand for the dose calculation of IMRT plan.
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Objective:To construct the curriculum content system of Extreme Environmental medicine based on the trainees' competency.Methods:After analysis of Chinese doctors' post competency demand, and the characteristics of military students, qualitative and quantitative methods were used to construct the curriculum system. The consistency of expert opinions was represented by Kendall's W coefficient, using chi-square test. The hierarchy and weights of all items were analyzed by the analytic hierarchy process, using consistency ratio ( CR) , which was incorporated into this system after passing the test ( CR<0.1) . Results:The selective experts were all authoritative and positivity, the assessments were consistency. Finally, it formed 5 primary items, 15 secondary items, and 54 third items of educational materials and 13 knowledge modules and 1 comprehensive seminar.Conclusions:Based on the demand of Chinese doctors' post competency, a curriculum system of extreme environment medicine has been constructed, through combined application of qualitative and quantitative research methods.
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Objective:To investigate the impacts of the composition and physical density of tissue on the dose distribution of implanted 125I seeds, in order to provide references for the clinical dose calculation and assessment of implanted radioactive particles. Methods:The OncoSeed 6711 physical model of 125I seeds was established using thes of twareegs_brachy and was validated through the calculation of dose rate constant and the radial dose function [ g( r)] in water. Then, based on the element composition and physical density of different types of tissue, the g( r) and absorbed dose ratein water, prostate, breast, muscle, and bone were calculated. Results:The calculated dose rate constant (0.950 cGy·h -1·U -1) and g( r)in water approached the values in related literature. The absorbed dose in bone was 6.042 times than that in water at a distance of 0.05 cm from the implanted source. The difference between the absorbed doses in breast and water was more than 10% at a distance of less than 1.7 cm from the implanted source. The difference between the absorbed doses in prostate/muscle and water was less than 5% at the same radial location. Conclusions:The dose distribution of 125I seeds in some types of human tissue is significantly different from that in water, which should be carefully considered in clinical dose calculation.
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Objective:To evaluate the impacts of tissue heterogeneity on dose calculation of cervical brachytherapy by comparing the doses calculated by two clinically used dose calculation method and the CT image-based Monte Carlo (MC) method.Methods:This study retrospectively selected 11 patients with cervical cancer treated with 3D brachytherapy in Anhui Provincial Cancer Hospital from January 2018 to June 2020. The dose distribution of each plan was calculated via three methods, dose calculation method described in American Association of Physicist in Medicine(AAPM) Task Group No. 43 Report (TG43-BT), Acuros BV(BV-BT) used to perform accurate dose calculations in high-dose-rate (HDR) brachytherapy with phantom heterogeneity, and CT image-based EGSnrc tool kit used to perform Monte Carlosimulation (MC-BT). The dose volumes( V3 Gy, V6 Gy, V9 Gy, and V12 Gy), target volume doses( D98, D90, D50), D2 cm 3 of organs at risk (OARs) calculated by the three methods were compared. Results:The HRCTV D90obtained by TG43-BT was 6.274 Gy, which was even overestimated by around 5% compared to the result calculated by MC-BT. Meanwhile, TG43-BT overestimated the dose volumesand the target volume doses compared to MC-BT.Except for D50 and V12 Gy, the differences between the doses to tumor calculated by BV-BT and MC-BT were not statistically significant( P>0.05). There was also no significant statistical difference between the D2 cm 3 of rectum, small intestine, and sigmoid calculated by BV-BT and MC-BT ( P>0.05). In contrast, the dose to D2 cm 3 of bladder determined by MC-BT was 4.609 Gy, which was notably higher than those deter mined by TG43-BT and BV-BT. Conclusions:TG43-BT overestimated the doses to tumor targets and most OARs since the effects of tissue heterogeneity were not taken into consideration. BV-BT performed efficient calculation and most of the dose distributionin target volume and OARs obtained by BV-BT were consistent with that calculated by MC-BT. Nevertheless, low accuracy occurred for the regions near the sources and full bladder, which warrants further caution in clinical evaluation.
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Objective To verify whether β-arrestin-2 inhibits autophagy by up-regulating PI3K/Akt signal to protect the liver from ischemia-reperfusion injury (IRI) in mice. Methods Twelve β-arrestin-2 knockout (KO) and twelve wild-type (WT) C57BL/6 mice were randomly divided into the KO+sham group, KO+IRI group, WT+sham group and WT+IRI group, six mice in each group. The mouse models with 70% liver IRI were established or sham operation was performed. Relevant experiments were carried out at 6 h after liver reperfusion or operation. The expression levels of apoptosis signal protein cleaved Caspase-3, proliferation signal protein Ki-67 and the PI3K/Akt signal protein p-Akt were detected by immunohistochemical staining. Results Immunohistochemical staining demonstrated that compared with the corresponding sham group, the positive cell count for cleaved Caspase-3, Ki-67 and p-Akt in liver tissues of mice was significantly increased in the KO+IRI and WT+IRI groups (all P < 0.01). Compared with the WT+IRI group, the positive cell count for cleaved Caspase-3 in liver tissues of mice was significantly increased, whereas the positive cell count forKi-67 and p-Akt was significantly decreased in the KO+IRI group (both P < 0.05). Conclusions β-arrestin-2 can mitigate the liver cell apoptosis and promote the repair of injury after IRI in mice. Moreover, β-arrestin-2 inhibits autophagy by up-regulating the PI3K/Akt signal to alleviate liver IRI in mice.
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Objective To investigate the effects of dilute concentration and acting time of pronase on quality of gastroscopy.Methods A total of 448 patients were randomly divided into two groups : sodium bicarbonate group and pronase with sodium bicarbonate group.Pronase was diluted into 50 ml (400 U/ml)and 100 ml (200 U/ml) using sodium bicarbonate.The patients were pretreated by pronase of different concentrations 10 min, 20 min, 30 min, 60 min and 120 min before gastroscopy.Diluent of same quantity were taken by the control group.Visibility of gastroscopy, procedure times and positive rates of lesions were compared.Results Pretreatment of pronase significantly improved visibility of gastroscopy, raised positive rates of lesions, and reduced procedure times of gastroscopy, compared with the control group (each P ＜ 0.05).The visibility of gastroscopy were over 80％ 20,30, and 60 minutes before the examination with no significant difference(P ＞ 0.05).The visibility of gastroscopy decreased sharply 30 minutes after taking pronase, especially after 60 minutes.There was no significant difference in the quality of gastroscopy between the 200 U/ml and 400 U/ml group 20-60 minutes before gastroscopy (P =0.640).Conclusion Pronase (200 U/ml-400 U/ml) significantly improves visibility of gastroscopy, raises positive detection rates of lesions, and reduces procedure time of gastroscopy 20-60 minutes before pretreatment.