Objective To evaluate the dosimetric characteristics of hippocampal formation (HF) in the intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC).Methods Fifty-nine NPC patients underwent IMRT.Simultaneous integrated boost technology was used to determine the doses for the target areas.The dose ranges of the HF were collected by dose-volume histogram.The influence of T stage on the exposure doses ( Dmax,Dmean,D20,V10,V20,V30,and V40 ) were compared.Results The maximum dose for the HF (Dmax) ranged from 11.1 to 78.2 Gy(F =24.2,P ＜0.05) and the Dmean ranged from 3.2 to 44.6 Gy ( F =16.3,P ＜ 0.05 ).The Dmax and Dmean of the T1-2 stage patients were (40.8 ±9.4) Gy and ( 12.5 ±5.1 ) Gy,respectively,both significantly lower than those of the T3-4 stage patients [ (58.6± 14.8) Gy,(20.9± 9.3 ) Gy].The mean exposed volume of the T4 stage patients was significantly larger than that of the T1 and T2 stages patients.Conclusions In the IMRT of NPC,the HF receives rather high irradiation dose.T stage is the main factor influencing the dose,especially T3 and T4 stages deserve serious attention.

Objective:To study the accuracy and positioning error of image guidance during the treatment of body stereotactic radiotherapy (SBRT) in patients with non-small cell lung cancer (NSCLC) by cone beam CT (CBCT) of VERO system.Methods:The clinical data of 80 NSCLC patients from January 2017 to December 2018 in Lishui People′s Hospital of Zhejiang Province were retrospectively analyzed. The maximum density projection and average density projection were reconstructed by four dimensional cone beam CT (4DCBCT), and internal target volume (ITV) was obtained by mapping the tumor profile. The translational and rotating tumor positioning errors were determined by comparing the manual ITV registration with the motion-fuzzy tumor on the CBCT. At the same time, correction was completed by the robot positioning bed and circular rotation. After correction, the CBCT was verified to evaluate the residual error.Results:The initial set average three dimensional vector displacement was significantly greater than the six dimensional automatic calibration displacement: (6.8 ± 2.1) mm vs. (1.5 ± 0.5) mm, and there was statistical difference ( P<0.01); 94.0% (425/452) of the rotation error was ≤ 3°. If there was no image guidance, the stereo positioning based on ExacTrac required 6.6 mm in the left-right direction, 9.8 mm in the up-down direction, and 6.5 mm in the front-back direction. After six dimensional correction of residual errors, the safety margins in three directions were reduced to 3.0, 3.2, and 3.1 mm, respectively. Conclusions:Online image guidance using ITV-CBCT matching technology and the automatic six dimensional correction of the VERO system can reduce the positioning error in SBRT treatment of NSCLC patients and improve the accuracy of tumor positioning.

Objective: To investigate the effect and mechanism of LncRNA ANRIL on the radiosensitivity of HCT116 cells line and nude mouse transplant tumors. Methods: The expression of LncRNA ANRIL in colorectal cancer cells was detected by qPCR. The negative control siRNA, ANRIL siRNA, miR-NC mimic, miR-195 mimic, miR-NC inhibitor and miR-195 inhibitor were transfected into HCT116 cells, and marked as negative control group, silencing ANRIL group, overexpressing miR-NC group, overexpressing miR-195 group, inhibiting miR-NC group and inhibiting miR-195 group, and the HCT116 cells without any treatment were marked as the blank control group. The clone formation assay was used to detect radiosensitivity of colorectal cancer cells, flow cytometry was used to detect apoptosis. The web site, StarBase, was used to predict the downstream miRNAs of ANRIL and dual luciferase reporter gene assay was used to further verify. Subcutaneous tumor transplantation assay was used to detect the effect of ANRIL on the growth of colorectal cancer cells after irradiation. Results: After irradiation with 2, 4, 6 and 8 Gy, the cell survival fraction of silencing ANRIL group was significantly decreased when compared with that of negative control group (P<0.05), and the radiosensitivity ratio was 1.52. The apoptosis rate of the silencing ANRIL+ 4 Gy group was significantly higher than that of the negative control+ 4 Gy group ((27.86±2.78)% vs. (12.06±1.46)%, P<0.05). The results of the experiment on nude mouse transplant tumors showed that the tumor volume in the negative control group was lower than that of the silent ANRIL group on days 13, 16, 19, 22 and 25 ((234±66) mm³, (273±63) mm³, (296±72) mm³, (321±85) mm³ and (403±94) mm³ vs. (357±79) mm³, (485±124) mm³, (617±143) mm³, (764±174) mm³ and (985±221) mm³P<0.05). MiR-195 is a target gene of ANRIL, and inhibition of miR-195 can reverse the inhibitory effect of silencing ANRIL on radiosensitivity, apoptosis and xenografts of HCT116 cells. Conclusions LncRNA ANRIL regulates the radiosensitivity of colorectal cancer cells by miR-195, which may provide a new sensitizing target for clinical colorectal cancer radiotherapy.