Objective To evaluate the value of imaging means on preoprative diagnosis for patients with malignant obstruction of the biliary and pancreatic ducts.[WT5”HZ]Method [WT5”BZ]44 cases underwent preoperative MR/MRCP/MRA examination. The accurate rate of diagnosis was compared with that derived from B us, CT and ERCP. Results 28 of 44 cases were diagnosed as with pancreatic and periampullary carcinoma, 5 cases as with pancreatic body and tail carcinoma,11 cases as with biliary duct carcinoma. The accurate rates of MR/MRCP/MRA for tumor locating and cause were 100% and 96% respectively. Blood vessel invasion, adjacent organ infiltration and matastasis were detected preoperatively in 17 cases. In contrast, the accurate rate for tumor locating and cause were 82% and 76% with CT, 73% and 68% with B us, 96% and 84% with ERCP. [WT5”HZ]Conclusions [WT5”BZ] MR/ MRCP /MRA combined has advantage over B us, CT and ERCP in preoperative diagnosis especially for detecting organ matastasis and blood vessel infiltration. It has an important value in the establishment of tumor staging and decision making of clinical therapy.

Objective To study the effect of leaf movement speed on the setup error of multileaf collimator (MLC) in RapidArc mode,and to improve quality assurance and verify the reliability of RapidArc.Methods Referring to the PicketFenceStatic_M120.dcm and PicketFenceRA_Ml20.dcm files,the Tilt tests with different adjacent leaf speed were designed and setup errors of MLC were obtained by analyzing electronic portal imaging device images.Results In the Tilt tests,the setup errors gradually increased from gapl 1 to gapS0 in both static gantry mode and RapidArc mode.With a gantry angle of 270°,gap41 had the maximum setup error of-0.55 mm.In the RapidArc mode,gap46 had the maximum setup error of-0.67 mm.The deviation of gap width was no greater than 15％ in any mode.There was no significant difference in deviation pattern of gap width between four modes with different gantry angles.The same gaps in different stripes showed a consistent trend in gap width.The RapidArc mode had a larger variation in percentage deviation of gap width than the static gantry mode.Conclusions The setup error increases with the increase in the speed of MLC leaf.The variation in the leaf speed has no significant impact on the gap width.There is no correlation between the leaf speed and the deviation of gap width.Four different gantry angles give similar deviation patterns of gap width,suggesting that the deviation of gap width is related to the leaf rather than the gantry angle.The RapidArc mode has a greater impact on the gap width than the fixed gantry mode.

Objective To investigate the role of N-acetylcysteine as a protective agent in rifampicin-induced hepatic injury of mice. Methods Thirth-two Kunming mice were randomly divided into four groups(n=8 each).The mice in each group were injected intraperitoneally with 0.9% sodium chloride solution (control), N-acetylcysteine (NAC), combination of rifampicin (R), or NAC and R (NAC+R) once every day.After 14 days, the liver index (LI), alanine aminotransferase (ALT) and aspartate aminotransferase ( AST) activity in serum, and the level of malondialdehyde( MDA) ,superoxide dismutase( SOD) activity in liver tissues were measured respectively.Hepatic tissue morphology was observed under light microscope. Results Macroscopic analysis revealed that rifampicin led to severe liver tissue injury,including a wide range of hepatocellular vascular congestion,fatty change and local necrosis, whereas the administrationof NAC produced a significant reduction of rifampicin-induced hepatotoxicity .LI,ALT and AST activities in R or NAC+R group were significantly elevated as compared with the control group(P<0.01) .LI, activities of ALT and AST in serum,and MDA levels in liver tissues in NAC+R group were significantly lower than those in R group ( P<0.01) ,but the SOD activity in NAC+R group was increased significantly in comparison with R group (P<0.01). Conclusion Rifampicin was able to cause severe hepatic injury.Pre-administration of NAC reduced the side-effect induced by the treatment with the rifampicin.

To produce the reverse transcriptase of moloney murine leukemia virus (MMLV-RT) through gene recombination, MMLV-rt gene was amplified by polymerase chain reaction (PCR) with specifically designed primers bearing restriction enzyme sites. Five mutation sites increasing the solution of the target protein were introduced through Site-directed mutation. After verification by sequencing, the gene was cloned into the expression vector pET15b to construct the recombinant plasmid pET15b-MMLV-rt. Purified MMLV-RT was obtained by affinity chromatography (Ni3+-NTA beads). Molecular weight and purity of MMLV-RT were analyzed with SDS-PAGE. Enzyme activity was characterized with RT-PCR. We successfully constructed the recombinant plasmid pET15b-MMLV-rt and obtained the MMLV-RT fusion protein with 6His on the N-terminus. Recombinant protein was purified through Ni3+-NTA beads based affinity chromatography, the purity of which was 96%. The Activity of the enzyme was high. MMLV-RT of 96% purity was obtained with the prokaryotic expression technique, which serves as the basis for mass production of this enzyme.
Animals ; Mice ; Moloney murine leukemia virus ; enzymology ; genetics ; RNA-Directed DNA Polymerase ; biosynthesis ; genetics ; Recombinant Fusion Proteins ; biosynthesis ; genetics ; metabolism ; Recombination, Genetic

Objective To study the dosimetric peculiarity of 3D intracavitary brachytherapy in the application of endometrial carcinoma comparing with traditional 2D plans. Method 39 3D brachytherapy treatment plans of 11 patients with endometrial carcinoma were retrospectively analyzed with re?planning 2D treatment plan, the dose volume histogram ( DVH) parameters such as the target dose volume parameters V150 and D90 , the 2?cc doses to organs such as bladder, small intestine, rectum and sigmoid and the total reference air kerma TRAK were analyzed. The differences between the two groups are compared by paired samples T test. Results For target with V<60 cm3 ,there is no statistically significant difference between 2D and 3D plans,the D90 is (551?17±90?33) cGy and (574?15±117?18) cGy,respectively (P=0?390). As the increase of target volume,the D90 came to be significantly different ( P=0?001) , high dose region V150 for 3D and 2D plans is (51?05±21?61) cm3 and (53?41±11?71) cm3, respectively (P=0?482). With the target volume larger than 60 cm3 ,compare to 2D plans, the 3D plan can increase the target coverage as well as OAR dose except for small intestine ( P=0?128) . In addition, with different plan mode,the BMI did not affect the crisis organ dose such as rectum, small intestine, bladder and sigmoid, the P value is 0?239, 0?198,0?744 and 0?834,respectively. Conclusions For endometrial carcinoma,compared with traditional two?dimensional plans,the 3D brachytherapy treatment plans can significantly improve the target coverage and avoiding overdose of organs, clinical curative effect and side effect still needs further observation.

Objective To determine the peripheral dose ( PD) of a Trilogy accelerator under different conditions and the feasibility of PD measurement using the semiconductor diode ionization chamber. Methods In a solid water phantom, a CC13 air?filled ionization chamber and a semiconductor diode ionization chamber were used for PD measurements with different distances (13 measurement locations within 1?31 cm) , depth ( 3, 5, 15 cm) , field sizes ( 10, 20, 30 cm) , wedge ( W15, W45, VW15, VW45) , and beam energy (6, 18 MV). The relationship of PD with PDleakage and PDscat er was determined by removing the scatter phantom. Simulating the patients with cervical cancer undergoing radiotherapy, a CIRS phantom received volumetric modulated arc therapy ( VMAT) , step?shoot intensity?modulated radiotherapy ( IMRT) , and sliding?window IMRT to measure PDs of the breast, thyroid, and lens. All the data were normalized to the isocenter. Results PD was gradually reduced with the increase in distance ( 13?41% at 1 cm from the edge to 0?25% at 31 cm from the edge) . With a fixed distance from the edge of the radiation field, there was no significant difference in PD between different depths. A radiation field with a size of 30 cm had a PD about two?fold higher than that with a size of 10 cm. PD increased with the increase in the physical wedge angle and increased by 1% compared with the open field;PD decreased with the increase in the virtual wedge angle and decreased by 2?3% compared with the open field. PD decayed from 13?35% at 1 cm to 0?23% at 31 cm under 6 MV X?ray and from 11?06% at 1 cm to 0?20% at 31 cm under 18 MV X?ray. Dscat er was dominant in the regions close to the edge of radiation field and decreased from 62?45% at 1 cm to 5?71% at 25 cm. In all measurements under 6 MV X?ray, the maximum proportion difference between CC13 ionization chamber and diode ionization chamber was less than 1%. PDs of the breast, thyroid, and lens were 6?72, 2?90, and 2?37 mGy in VMAT mode, 7?39, 4?05, and 2?48 mGy in step?shoot IMRT mode, and 9?17, 4?61, and 3?21 mGy in sliding?window IMRT mode, respectively. Conclusions For the measurement of PDs, the CC13 air?filled ionization chamber and semiconductor diode ionization chamber have good consistency and feasibility under 6 MV X?ray. In clinical practice, the understanding of the relationship of PD with different radiation conditions helps to reduce the doses to organs at risk. Shielding and protective techniques can further reduce dose deposition.

Objective:To discuss the design details of accelerator room for a novel enclosed O-ring linac Halcyon, and to optimize its protection and layout.Methods:According to the optimization principle of radiation protection and the requirements of national radiation protection standards, and the structural characteristics of Halcyon accelerator, the differences between conventional and this novel accelerator rooms were analyzed by discussing the space layout of the machine room, shielding calculation, electrical facilities, purifying ventilation, temperature and humidity control and other factors.Results:The Halcyon machine had a compact structure, a closed ring frame design and a main beam shielding device, which could greatly reduce the radiation protection pressure while improving the space utilization rate of the machine room. The optimized design layout of the machine room could eliminate hidden dangers, avoid design defects, and prevent adverse consequences caused by design errors.Conclusions:The overall structure of Halcyon accelerator is different from that of conventional accelerators. The design details should be taken into full consideration to ensure the optimization of radiation protection, lay a good foundation for subsequent installation, debugging and operation of the equipment and create a good treatment environment for patients and medical staff.

Objective:Objective To investigate the role of radiotherapy in the treatment of refractory keloids, evaluate the self-assessment degree of satisfaction of patients and compare with the objective outcomes.Methods:A total of 144 patients (290 lesions) with refractory keloids admitted to Peking Union Medical College Hospital from 2013 to 2018 were included in this study. The median age was 28 years old (range: 15-81 years old). All lesions were subjected to electronic radiation at postoperative 24h. The regime of 5 to 7MeV electron beam radiation therapy was adopted. The total dose was ranged from 16 to 18 Gy/2f (at 1-week interval). The median follow-up time was 48 months (range: 35-91 months). Patient and Observer Scar Assessment Scale (POSAS) was used to evaluate the degree of satisfaction. Multivariate analysis was performed by Cox proportional hazards model.Results:Among 290 keloids, 52 keloids (17.9%) relapsed in 3 to 42 months from the end of radiotherapy (median 12 months). The main side effects were hyperpigmentation and local incisional extension. Univariate analysis showed that local incisional color darker than skin, pruritus, pain and young age were associated with recurrence. Multivariate analysis indicated that local incisional color darker than skin and pain were the independent prognostic factors for scar recurrence. Recurrence, hyperpigmentation and local incisional extension were the main reasons for patients′ dissatisfaction.Conclusions:Postoperative electronic radiation can achieve satisfactory efficacy in the treatment of refractory keloids. Local incisional color darker than skin and pain are the independent prognostic factors of keloid recurrence. Patient self-assessment results are not fully consistent with the objective clinical outcomes and recurrence status.

Objective:To investigate the urinary iodine and thyroid volume of children aged 8 to 10 years in Linhai City Zhejiang Province, and evaluate the iodine nutrition level of children so as to provide a basis for formulating intervention measures to eliminate iodine deficiency disorders.Methods:In 2019, a systematic sampling method was adopted to select 1 township (street) central primary school in each of the 5 areas in the east, west, south, north, and middle of Linhai City. At least 40 children aged 8 to 10 years were selected from each of the central primary schools in each township (street) to collect family edible salt samples and one-time urine samples during the day for salt iodine and urinary iodine testing, respectively, as well as thyroid B-ultrasound examination.Results:A total of 215 salt samples were collected. The median salt iodine was 21.0 mg/kg, the coverage rate of iodized salt was 57.2% (123/215), the qualified rate of iodized salt was 91.9% (113/123), and the consumption rate of qualified iodized salt was 52.6% (113/215). A total of 215 urine samples were collected. The median urinary iodine was 166.0 μg/L, and the proportion of urinary iodine < 50 μg/L accounted for 5.1% (11/215). A total of 215 children were examined, and the goiter rate was 4.7% (10/215).Conclusion:The overall iodine nutrition level of children aged 8 to 10 years in Linhai City is at an appropriate level (100-199 μg/L), and the goiter rate is within the standard limit for the elimination of iodine deficiency disorders (5%), but the coverage rate of iodized salt and the consumption rate of qualified iodized salt are seriously low.

Objective To analyze the failure and processing methods of helical tomotherapy multileaf collimator (MLC) and summarize relevant maintenance experience,aiming to accurately identify the faulty parts,shorten the downtime and enhance the work time.Methods The failure data of the helical tomotherapy MLC system in the past 48 months were analyzed to identify the common faulty parts,causes and processing methods.Results During the previous 48 months,the MLC failure occurred for 20 times,11 times for air compressor failure,4 times for position verification board failure,twice for leaf driver failure,twice for cushion valve failure and once for the slip of leaf position verification rod.The MLC failure was significantly correlated with the humidity of high-pressure gas.The work time of machine exerted significant effect upon the service time of MLC parts.Conclusions The structure of the helical tomotherapy MLC system is complex.The high-intensity work increases the failure rate.The humidity of high-pressure gas affects the normal operation of the MLC equipment.The faulty parts can be identified,the downtime can be reduced and the work time can be enhanced by summarizing the experience of MLC maintenance.