Objective To evaluate the uncertainty of the small bowel dose?volume and the normal tissue complication probability (NTCP) during intensity?modulated radiotherapy (IMRT) for rectal cancer, and to provide a reference for the dose limit and protection of the small bowel during IMRT for rectal cancer. Methods A total of 20 patients with rectal cancer who received postoperative adjuvant radiotherapy from March 2014 to August 2015 were enrolled in this study, including 10 patients receiving CT scan in the supine position and 10 patients in the prone position. All patients received computed tomography ( CT) scan before the treatment and at weeks 1, 2, 3, and 4 of treatment, and they were defined as Plan, 1W, 2W, 3W, and 4W CT groups, respectively. The small bowel loop ( BL ) and peritoneal space ( PS ) were delineated on the images. The IMRT plan based on the Plan CT was copied to the 1W, 2W, 3W, and 4W CT groups, and then the small bowel dose?volume and NTCP were assessed for all CT groups. The paired t?test was used for comparison between groups. The Pearson method was used to analyze the correlation between NTCPC(chronic NTCP) and dose?volume. Results A total of 89 CT images of 20 patients were obtained. In all the patients, the volumes of BL and PS were 25121 cm3 and 132416 cm3 , respectively, and the shift% was 2315% and 1134%, respectively. The V15 of BL and PS was 18486 cm3 and 79245 cm3 , respectively, and the shift% was 3169% and 370%, respectively. The V30 of BL and PS was 8801 cm3 and 64573 cm3 , respectively, and the shift% was 3766% and 1049%, respectively. The V15 of BL in 35% of patients and V15 of PS in 20% of patients, the Dmax of BL in 50% of patients, and the NTCP of 15% of patients in the course of treatment exceeded the safety limits. The 1?4W CT groups had a significantly higher NTCPC than the Plan CT group (402% vs. 320%, P=0104), and their SD% was 4168%. There was a significant correlation between NTCPC and V30?V50 of BL (R>0400, P=0000). The NTCPA ( acute NTCP ) and NTCP C in the supine position were significantly higher than those in the prone position ( 6230% vs. 5674%, P=0061;488% vs. 322%, P=0145 ) . Conclusions Small bowel motility leads to an uncertainty of the adverse event assessment during IMRT for rectal cancer. The change in BL is significantly larger than that in PS and the change in BL and PS in the supine position is significantly larger than that in the prone position. Using the prone position and minimizing V15 and V30 when designing the treatment plan can reduce the NTCP A and NTCP C in the small bowel.

Objective To compare the dose volume and normal tissue complication probability (NTCP) of small intestine between intensity-modulated radiotherapy (IMRT) with dose constraints to the peritoneal space (PS) and the bowel loop (BL) in the treatment of rectal cancer,and to investigate the feasibility of placing a dose constraint to the PS instead of the BL in protection of the small intestine.Methods A total of 24 patients with rectal cancer undergoing postoperative adjuvant radiotherapy were enrolled as subjects.In the 24 patients,12 were treated in supine position an.d 12 in prone position.The weekly computed tomography (CT) scans from pre-treatment to weeks 1-4 of treatment were defined as Plan,1 W,2 W,3 W,and 4 W.Contours of PS and BL were delineated on all CT images.Based on the Plan CT images,two IMRT plans,PPS and PBL,were designed with dose constraints to the PS and BL,respectively.The method was applied to 1-4 W CT images.For each CT scan,the dose volume and NTCP of the small intestine were evaluated in PPs and PBL.Results A total of 109 sets of CT images were acquired from 24 patients,and 218 plans were designed and copied.The median volume of the PS and BL was 1339.28 and 250.27 cm3,respectively.For the Plan CT scans,V15 values of the PS in PPs plan and the BL in PBL plan were 918.96 and 199.57 em3,respectively.For all CT scans,the dose volume of the small intestine in PPs,in most cases,was lower than that in PBL,while V15 values in Ps and PBL were 170.07 and 178.58 cm3 (P=0.000).The dose volume of the small intestine was correlated with V15 (P=0.000).PPs had significantly lower NTCP of chronic and acute adverse reactions than PBL(2.80％ vs.3.00％,P=0.018;57.32％ vs.58.64％,P=0.000).In patients with prone and supine treatment positions,most of the dose volume and NTCP of the small intestine in Ps were significantly lower than those in PBL(P＜0.05 for V10,V15,V30,and NTCP of acute adverse reactions).Conclusions It is feasible to place a dose constraint to the PS instead of the BL for protection of the small intestine during IMRT for rectal cancer.V15＜830 cm3 can be referred to as the objective function of dose restraint.

ObjectiveTo investigate the relationship between 10 cGy whole brain radiation and cognitive dystunction.MethodsThirty-two male Sprague-Dawley rats at age one month were randomized into irradiation and sham exposed groups.Behavioral and histopathological tests were performed 3 months after irradiation in the order of open field,Morris water maze,passive avoidance,and histopathological test.Comparison between the two groups was conducted using independent samples t-test.ResultsIn the place navigation test of Morris water maze,irradiation group showed significantly longer latency than sham exposed group on day 3 and 4 ( t =2.91 and 2.65,all P ＜ 0.05 ).In the total latency of the place navigation,irradiation group also presented longer latency comparing with sham exposed group ( t =2.63,P ＜ 0.05 ).In the spatial probe test of Morris water maze,the open field test and the passive avoidance test showed no significant difference between the two groups ( t =0.92,0.59,0.83,all P ＞ 0.05 ).The histopathological examination had no significant difference either.ConclusionWhole brain radiation of 10 cGy could partly injury the cognitive function of the rat.

Objective To investigate the effect of hydrogen on radiation-induced acute injury in rat brain.Methods Forty-five mature Sprague-Dawley rats were randomly divided into three groups:saline therapy group,hydrogen therapy group and healthy control group.The whole brain of SD rat was irradiated with single dose of 20 Gy by 4 MeV electrons.Rats in therapy group were injected with hydrogen-rich saline after irradiation and were sacrificed at 1,3,7,14 d post-irradiation.The changes of malonaldehyde (MDA),superoxidase dismutase (SOD) and 8-hydroxydeoxygunosine (8-OHdG) in brain homogenate and the pathological changes in brain hippocampus were observed.Results The brain water content (t=3.78,3.18,P＜0.05) and the contents of 8-OHdG (t=2.33,2.71,2.33,P＜0.05) in the therapy group was lower than the control group at 7 d and 14 d post-irradiation.The contents of SOD were significantly higher(t =2.41-2.92,P ＜ 0.05) from 1 to 7 day,while the contents of MDA were significantly lower in therapy group than those in the control group from 1 to 14 day post-irradiation (t =4.01-6.20,P ＜ 0.05).Moreover,the damage degree in the nerve cells of hippocampus was less compared to the control group.Conclusions The hydrogen-rich saline could have protection role in irradiation-induced acute brain injury in rats.

Objective To investigate the impact of actual gantry angle on the accuracy of intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC). Methods A total of 27 patients with NPC were enrolled in this study. IMRT plans were designed with Pinnacle treatment planning system (TPS),and 8 beams with an interval of 30°(within 0°-360°) were selected for each plan. These plans were divided into plan A and plan B according to the beam parameters. In plan A,the minimum sub-field area was 5 cm2 ,the minimum number of sub-field monitor unit ( MU) was 5,and the maximum sub-field number was 80;in plan B,the minimum sub-field area was 8 cm2 ,the minimum number of sub-field MUs was 8,and the maximum sub-field number was 60.The gamma passing rate using the criteria of 3%/3 mm and 2%/2 mm at actual and zero degree gantry angles were calculated using Mapcheck 2 device for dose verification,and were compared with the paired t-test. The relationship between the above differences (Δ value) and the beam angle or the beam parameters was also analyzed. Results In plan A with the criteria of 3%/3 mm, the beams were significantly different (P=0000-0007) except for at angles of 270°,300°,and 300°,and the mean Δ value was 090%;under the criteria of 2%/2 mm,all beams were significantly different ( P=0000-0019) except for at an angle of 300°,and the meanΔvalue was 272%.In plan B with the criteria of 3%/3 mm,the beams showed no significant difference ( P=0052-0639) except for at an angle of 300 ° ,and the mean Δ value was 040%;under the criteria of 2%/2 mm,all beams showed no significant difference ( P>005) except for at angles of 210°,240°,270°,and 300°,and the meanΔvalue was 152%.When the plan B parameters were used, the Δ value was reduced;the results of two verification methods were more consistent,so the accuracy was also improved. Conclusions Compared with the validation method at zero degree gantry angle,the validation method at an actual gantry angle is associated with reduced gamma passing rate because of some factors such as gravity,which is not significantly related to the beam angle,but the beam parameters. In the design of IMRT plans for NPC,the total number of sub-fields should be decreased as far as possible,and the minimum sub-field area and the minimum number of MU should be increased, so as to improve the accuracy of treatment plans.

Objective To assess the protective effect of low melting point lead and field margin on the opposite testicular in testicular seminoma patients during postoperative radiation.Methods A patient with stage Ⅰ seminoma was selected and his phantom measurement was carried out.The PTW 0.6 cm3 type ionization chamber was used to measure the absorbed dose under the conditions of no lead and low melting point lead with thickness of 3,5,7,10 and 15 mm at different distances from the field edge,respectively.Results Under different lead thickness conditions,the measurement result and the distance between the measured points and the boundary of the field were exponentially attenuated.The relative target dose dropped from 8.41％ at 1 cm to 0.61％ at 25 cm without lead blocking,and dropped from 4.55％,3.98％ and 3.47％ at 1 cm to0.27％,0.21％ and0.17％ at 25 cm with 3,5,7 cmlead,respectively.With 10 mm lead,it dropped from 2.55％ at 1.5 cm to0.15％ at25 cm,and 1.86％ at2 cm to0.13％ at 25 cm with 15 mm lead.The lead shield of 3,7 and 15 mm thickness can be used to reduce the scatter dose of testis to below 0.5 Gy during radiotherapy for seminoma.Conclusions An appropriate thickness of low melting point lead might reduce the dose of testis conveniently and effectively,which would be beneficial to protect the fertility of the patients with testicular seminoma.

Objective To compare the effect between the supine and prone patient positions upon target dose coverage during intensity-modulated radiotherapy (IMRT) for rectal cancer, aiming to provide clinical reference for the selection of position for rectal cancer patients. Methods Twenty-four patients diagnosed with rectal cancer receiving postoperative adjuvant radiotherapy were selected and divided into the supine (n=12) and prone position groups(n=12). Before and during the IMRT(1-4 weeks),all patients received CT scans, which were defined as:Plan,1W,2W,3W and 4W,respectively. The organs at risk were delineated based on CT scan images. Plan,1W, 2W, 3W and 4W CT scan images were fused. The CTV and PTV from Plan CT scan were copied to the 1-4W CT scan images,and the therapeutic plans from Plan CT scan were copied as well. The target dose coverage was assessed and the failure rate of target dose coverage was calculated. The couch-position data for each patient during each cycle of IMRT were recorded by using the MOSAIQ network and the overall deviation (S) of couch position was calculated. Results The failure rates of CTV and PTV target dose coverage in the prone position group were higher than those in the supine position group (18.60% VS 0%, 69.76% VS 53.65%).The S value was significantly correlated with the target dose coverage (r=-0.683,P=0.000). The S value in the prone position group was(1.23±0.76) cm,significantly greater than(0.28±0.18) cm in the supine position (P=0.001),and the most significant deviation was noted in the y (head and foot) and z (frontal and dorsal) directions (P=0.003 and 0.003). Compared with the supine group,the V5and V10 of the small intestine were significantly less (P=0.003 and 0.004) and the chronic toxicity (NTCPC) was considerably reduced(P=0.041) in the prone position group. Conclusions A better target dose coverage can be maintained during IMRT with a supine position during rectal cancer IMRT, whereas the positioning repeatability is worsened with a prone position due to use of the belly board, thereby affecting the target dose coverage. Although the prone position combined with belly board can reduce the tolerated dosage of the small intestine,effective measures should be taken to guarantee the patient positioning repeatability.

Objective To evaluate the effects of neural stem cells (NSCs) overexpressing brainderived neurotrophic factor (BDNF) on the levels of neurotrophic factors and microglia activation in hippocampus after brain irradiation.Methods Hippocampal NSCs were isolated from fetal rat brain and infected with GFP-lentivirus and GFP-BDNF-lentivirus.SD rats were randomized into four groups:control group,irradiated group (R group),GFP-modified NSCs transplantation group with irradiation (R+NSCs group),and GFP-BDNF modified NSCs transplantation group with irradiation (R+BDNF-NSCs group).NSCs were transplanted into the bilateral hippocampus of rats one month after whole brain irradiation at a single dose of 20 Gy.The expressions of BDNF,glial-derived neurotrophic factor (GDNF) and nerve growth factor (NGF) in hippocampus were detected at 2 and 8 weeks after transplantation.The activation of microglia was observed by immunofluorescence.Results At 2 and 8 weeks after transplantation,the expressions of BDNF and NGF proteins in hippocampus of R+BDNF-NSCs group were significantly higher than those of R group (P＜0.05).The activated microglia in the R+NSCs group and the R+BDNF-NSCs group had no decrease compared with R group (P＞ 0.05).Conclusions The transplantation of NSCs overexpressing BDNF promotes the production of BDNF and NGF,which improves the level of neurotrophic factors in hippocampus after radiation.

Objective: To investigate the influences of antibiotic-induced gut microbiota dysbiosis on Mycoplasma pneumoniae (Mp) airway infection. Methods: C57BL/6J mice were treated with vancomycin and gentamicin for 21 d by oral delivery and then intranasally infected with Mp. Quantitative real-time PCR (qPCR) was performed to detect five major phyla of gut microbiota in mouse fecal specimens before and after antibiotic treatment and the loads of Mp in lung tissues on 3 d and 7 d after infection. Pathological changes in lung tissues were evaluated with HE staining. IFN-γ and IL-4 secreted by spleen CD4⁺ T cells and CD8⁺ T cells were analyzed by flow cytometry. Mp-specific IgM and IgG in mouse serum samples were measured by indirect enzyme-linked immunosorbent assay (ELISA). Results: Vancomycin and gentamicin treatment significantly reduced the number of Bacteroidetes in mouse feces, but increased the amount of Firmicutes. Meanwhile, the numbers of δ, γ-Proteobacteria, Actinomycetes and Tenericutes also changed. These antibiotic-induced gut microbiota alterations in mice with Mp infection increased the loads of Mp in lung tissues and the pathological scores of lung tissue inflammation on 3 d and 7 d after infection, and reduced the number of IFN-γ-secreting spleen CD4⁺ T lymphocytes on 7 d. Conclusions Antibiotic-induced gut microbiota dysbiosis aggravated Mp airway infection.