Objective To study the effect of the custom of long term chewing lime tobacco on human tooth enamel electron spin resonance (ESR) dosimetry. Methods A total of 20 enamel samples from lingual parts of adults teeth collected in Bombay, India were obtained by mechanical method. Some enamel samples from Japanese adults were extracted and 10 mixed samples were prepared. Enamel samples were exposed to different doses of 60Co γ-rays several times, and ESR spectra were measured after exposure. Results ESR background signals of 9 Bombay samples were found 1.5-3.3 times higher than those of Japanese mixed samples. The γ-ray dose responses of dosimetric signal with higher background level were a little lower, and the average sensitivity was (0.42 ± 0.03 )mGy, which was close to that of Japanese mixed samples. Conclusions The average level of background signals of Bombay samples was much higher than that of other non-chewing tobacco area, which was possibly caused by tobacco lime, the main component in chewing tobacco productions, and it would help to explore its special influences on ESR, and improve dose reconstruction in accuracy.

Objective:A database was designed and developed for effective utilization monitoring data of radiation dose to patients and occupational operators in cardiovascular interventional procedures. Methods:To complete a command reception of the client program, data display and other functions, compiled database software using MS Visual Basic level programming language. Using MS Access database completed data storage, management and maintenance. Results:The database was designed according to technological indicator acknowledged;the relevant help file was set up. The database includes two sub-libraries professional database and patient database. Professionals and patients can be recorded separately input, record view and record query. Conclusion:The data platform for monitoring data of radiation dose in cardiovascular interventional procedures was provided, which can provide basic data for constituting normalization and technical standard of dose limited of radiation dose to patients and occupational operators in cardiovascular interventional procedures.

Objective:To complete experiments of the energy response compensation for three semiconductor personal dosimeters in order to meet the requirements of IEC and National Standard.Methods: In Beijing SSDL, the semiconductor detectors were covered by the different thicknesses of Pb and Sn additional filters with several diameter holes to compensate the dosimeters’ energy response.Results: At the 50 keV-Cs-137 energy range, the measuring error of dosimeters is met within 30% of energy response.Conclusion:By the compensation of combined Pb and Sn filters with a hole, the semiconductor personal dosimeters can be used for radiation monitoring.

Objective:According to the requirement of ISO and National Standard, new X-ray environmental standard for the calibration of environmental dosimeter was established in Beijing SSDL. Methods:Half value layer and air kerma dose-rate was determined in the X-ray environmental qualities by a standard dosimeter. Results: The technical requirement of ISO and National Standard are met within 2% for the X-ray environmental standard qualities in Beijing SSDL. Conclusion:The X-ray standard radiation field can be used for the calibration of environmental dosimeters and experiment of research.

Objective To investigate solar radiation and its effects on human tooth enamel electron spin resonance (ESR) dosimetry. Methods 11 tooth enamel samples were prepared by mechanical method. The intensity of solar iUuminanee was measured with a light meter, the measured illuminance was converted to insolation using a coefficient. Summation of solar radiation was evaluated. Enamel samples were exposed to 60 Co γ rays followed by sunlight on sunny days, and ESR spectra were scanned after different exposure. Results The solar radiation to the samples was (580 ± 16) MJ/m2. Solar exposure also caused dosimetrie signal. The perpendicular component of dosimetrie signal increased linearly with the amount of solar radiation, another signal close to background tended to saturation. Conclusions The average effect of the solar radiation on the signal was be used to recognize the effect of solar radiation on the enamel, and estimate external dose accurately.

Objectlve To study the properties of goat tooth enamel electron spin resonance (ESR)dosimetry.Methods Tootll enamel samples of goats were achieved by combined mechanical and chemical treatment at the ages of l,2,3,5,and 6 years.respectively and 9 enamel samples of adult molar were obtained.These enamel samples were exposed to 137Cs γ-rays at the cumulative doses of 0,0.5,1.0,2.0,and 5.0 Gy,respectively.ESR spectra Was measured before and after exposure.Results The background signal of goat tooth samples W88 21.5,significantly lower than that of the adult molar samples(39.5).The dusimetric signal intensity of the goat enamel increased with the radiation dose in a linear manner just as that of the human molars.The average radiation sensitivity of the goat tooth samples was(34.3±1.9)/Gy,close to that of the human tooth samples.Conclusions Goat teeth can be used for retrospective radiation dose reconstruction when human teeth are unavailable,in order to previde scientific data for dose reconstruction accurately.

Objective To develop the methods for using 0.015 cc pinpoint chambers, 0.007 cc miniature chambers and diode detector to measure Multi-leaf collimator (MLC) small field in IMRT.Methods MAX4000 and Unidos electrometers were connected with different types of small chambers and diode detectors.MLC shaped fields of10 cm×10 cm, 6 cm×6 cm, 4 cm×4 cm, 3 cm×3 cm, 2 cm× 2 cm were defined at 100 cm SSD.The field sizes for the Varian accelerator were defined by the tertiary MLC, while the secondary jaws were kept at 10 cm × 10 cm field, with the monitor units of 250 MU.Each field was measured three times to obtain the average value.The readings of all small fields were normalized to 10 cm × 10 cm field values for comparison of measured and published output factors.Results The relative deviations of the MLC small field output factors from the published outputs are 1.0％ , 1.7％ , 1.5％ and 2.4％, respectively, for Unidos electrometer connected with 0.015 cc pinpoint chamber;0.2％, 0.8％, 0.8％ and 1.4％, respectively, for Unidos electrometer connected with 0.007 cc miniature chamber;and 0.1％, 0.5％, 0.5％ and 0.9％, respectively, for MAX4000 electrometer connected with 0.007 cc miniature chamber.Conclusions The 0.015 cc chamber-measured MLC output factors for 3 cm × 3 cm and 2 cm × 2 cm fields are excellent.As required by IAEA, the relative deviations of the measured output factor from the published output factor are within ± 2％ for 2 cm × 2 cm fields and ± 3％ for larger fields.The results measured using 0.007 cc chamber are better than those measured using 0.015 cc chamber.The measured results using the diode detector, normalized to the 10 cm × 10 cm field, are consistent with the minimum requirements and excellent when being normalized to the 4 cm × 4 cm field.For dosimetric consideration, MLC small field output factor should be measured using small chamber and diode detector.The method is accurate and reliable, therefore, all measured output factors for MLC small fields should be input into radiation treatment plan system.

AIM: To decide the effect that selected siRNA degrades mRNA of IL-1? specifically and suppression of its expression after connected with target site with homology complementary sequence. METHODS: Synthesized DNA expression box aimed directly at target site through PCR reaction in vivo was purified, and transfected into lymphocytes stimulated by LPS. siRNA was transcribed by cellular endogenous RNA polymerase Ⅲ and then evoke the degradation of target mRNA. After 48 hours of transfection, the cell culture supernatant was collected and the concentration of IL-1? was assayed using ELISA. RESULTS: Compared with blank-control and negative-control, selected sequence decreased the expression of IL-1?. Rate of the suppression was about 15%. CONCLUSION: RNAi technology produces specific interference effect in mouse spleen lymphocytes in original culture and inhibits the excretion of IL-1?.

Objective To establish a new method to analyze the position accuracy of multileaf collimator (MLC) in the dynamic mode.Methods The MLC test sequence was created in a field,where intentional leaf positional errors ranging from 0.1 to 1 mm per centimeter were introduced.In order to establish the relationship between the ion chamber readings and leaf position,whose slope indicated the leaf position error per centimeter,a two-dimensional ion chamber array was used to measure absorbed dose while leaves were moving at dose rates of 100,300 and 600 MU/min,respectively.For routine test,leaf position error was easily found via dose profile in y direction of the field created by dynamic leaves,where the position error could be quantitatively calculated as the slope of absorbed dose line of x direction of the same field.Results The error of 0.2 mm or more per centimeter was obviously shown through y dose profile.The calibration curve was linear at different dose rates.At 600 MU/min,a 0.1 mm leaf position error corresponded to a slope variation of 0.74％,and the differences between the tested errors and the introduced errors were within 0.1 mm.Conclusions The simple and reliable method is helpful to establish the intensity modulated radiation therapy (IMRT) quality control (QC) system.

Objective:To enhance the capabilities of individual monitoring technology services for external exposure.Methods:The intercomparison results of the national individual monitoring for external exposure during 2015-2019 were presented, together with a summary and analysis provided of the main existing problems.Results:By 2019, 382 of individual monitoring technology service uints, from 30 provinces, autonomous regions or municipalities, participated in the individual monitoring intercomparisons results, involving disease control and prevention centers, occupational prevention and control institutions, research institutes, universities, nuclear industry, medical institutions, and companies. Except for slightly low in 2017, the pass rate in the other four years was above 90%. The excellence rate increased with the years.Conclusions:The capabilities of individual monitoring service units can meet the concerned requirements and provide standardized monitoring report for the period of 2015 to 2019, but with some being unqualified. These service units should carefully analyze and identify the reasons for the failure, standardize the quality control of laboratory, and improve the level of measurement and the ability of data analysis.