Objective To study the effect of radon exhalation on the external dose model for building material,so as to provide the scientific and precise assessment of external radiation exposure hazard.Methods The mechanism of exhalation of radon from building material was analyzed,mathematical model of correction factor for the effect of radon exhalation was derived and resolved by Matlab program and the relationship between correction factor and diffusion length,surface emanation coefficient and thickness of building material was discussed.The absorbed dose rate induced by several classical building materials was calculated and compared.Results The radon exhalation correction factor was independent of diffusion length and thickness of building material in most cases.Negative correlation was found between radon exhalation correction factor and radon surface emanation coefficient.Radon exhalation correction factor numerically equals to '1-radon surface emanation coefficient'.The relative percentage deviation between absorbed dose rate induced by several classical building materials was in the range of 2.23％-10.02％,for both corrected and uncorrected radon exhalation effects.Conclusions Radon exhalation from building material has a certain effect on external dose model for building material,which should attract attention.It is important to conduct the correction for external dose model by introducing ‘1 -radon surface emanation coefficient’ as the radon exhalation correction factor,in order for the scientific assessment and control of external radiation exposure hazards from building materials.

Objective To investigate the current situation of radiation protection in nuclear medicine diagnosis workplace.Methods The study was performed in 3 hospitals in northeast,north and central of China from February to December in 2013.The γ dose rate instrument was used to detect the workplace ambient dose equivalent rate of medicine preparation,leaching,packing,injection and imaging.Individual effective dose and equivalent dose were evaluated by photoluminescent dosimeter.Results The ambient dose equivalent rate was up to 1.92 mSv/h at repacking place and 1.2 mSv/h at injection place.The ambient dose equivalent rate of patients after injection was 5.36-240 μ,Sv/h.The hand equivalent dose was 0.01-0.02 mGy.Moreover,there were problems of staff route intersection,as well as the patients after injection staying in the public area.Conclusions Radiation workers should pay more attention to individual protection,and improve the operation proficiency to shorten the operation time.Furthermore,in order to protect public from unnecessary irradiation,there should be some changes in staff route and patients administration.

Objective To measure the circuit time constants of 4 kinds of radiation survey meters (451P ionization chamber dosimeter,6150AD6 + 6150AD-b dose meter,FH40G + FHZ672E-10 dose meter and AT1123 dose meter) and,to discuss the formula of time response correction and its application.Methods In the condition of continuous exposure of X-ray machine,the ambient dose equivalent rates shown by survey meters were recorded.In order to get the circuits time constant,the least squares fittingmethod was used to fit the data using the time response formula of circuit having a capacitance C and a resistance R in series.Results The relative uncertainty of fitted circuit time constants was higher than 20％ except for 6150AD6 + 6150AD-b dose meter.The relative uncertainty of fitted r was 8％ for 6150AD6 + 6150AD-b dose meter.Conclusions The time required to stabilize the dosimeter readings was 8,5,3 and 2 s,respectively,for the 451P ionization chamber dosimeter,6150AD6 +6150AD-b dose meter,FH40G + FHZ672E-10 dose meter and AT1123 dose meter.The rising trend of their measured values was not fully accordance with the RC circuit time response correction formula.

Objective:To verify and discuss the consistency and applicability of the semi empirical formula and Monte Carlo simulation method in the radiation shielding calculation for high energy synchrotron radiation source.Methods:The semi empirical formula and Monte Carlo simulation were used to calculate the ambient dose equivalent outside of the shielding.Results:The ratio of Jenkins semi empirical formula result to Monte Carlo simulation result was 111%-153%. The ratio of Sakano semi empirical formula result to Monte Carlo simulation result was 201%.Conclusions:For a single shielding material, the semi empirical formula can be simple and conservative to complete the shielding calculation for high-energy electron accelerator. For a variety of shielding materials, Monte Carlo simulation method should be used.

Objective To use Monte Carlo method to build a shielding calculation model for the proton and heavy ion treatment room,and to provide a reliable calculation method for shielding design.Methods A Monte Carlo-based FLUKA code was adopted to build the shielding calculation model for the proton and heavy ion treatment room,and to simulate the radiation field distribution in the proton and heavy ion treatment room.The calculation model was verified through the radiation detection around the proton and heavy ions treatment room.Results The FLUKA code-based simulation results were consistent with the radiation detection.Conclusions The shielding calculation model based on FLUKA code can simulate the radiation field from proton and heavy ions.Among the secondary particles,secondary neutrons are the dominant component and the main concern of accelerator shielding design.In shielding calculation,the emphasis should be put on both beam intensity and energy.

Objective To compare the value of diffusion kurtosis imaging (DKI) model with single-index DWI model parameters in the differential diagnosis of benign and malignant breast lesions,and to explore the correlation between the parameters and molecular subtypes and prognostic factors of breast cancer.Methods A retrospective analysis was performed with inclusion of 64 cases of breast diseases from January 2016 to May 2017 in Shanghai First People's Hospital.The patients were pathologically confirmed and typed, 30 cases are malignant tumors and 34 cases are benign lesions. DKI and DWI were performed within 2 weeks before the pathological examination. Invasive ductal carcinoma of grade Ⅰ, Ⅱ and Ⅲ were revealed in 1, 7 and 13 cases respectively. Luminal A breast cancer was found in 10 cases, Luminal B breast cancer was diagnosed in 11 cases, HER-2 positive breast cancer was 4 cases and triple negative breast cancer was 5 cases. The expressions of estrogen receptor (ER), Progesterone receptor (PR), and HER-2 positive were found in 20, 14 and 15 cases respectively. Ki67 was highly expressed in 24 cases and low expression in 6 cases. All patients underwent both plain and enhanced mammography scanning. The kurtosis (MK), mean diffusivity (MD) and ADC value were measured. Prognosis analysis was performed according to the maximum diameter (>2 cm, ≤2 cm), vascular or neurological invasion (positive, negative), lymph node metastasis (positive, negative), ER (positive, negative), PR (positive, negative), HER-2 (positive, negative),Ki67 (positive, negative), pathological grade (grade Ⅰ+Ⅱ,Ⅲ). Two independent samples t test was used to compare DKI and DWI parameters between benign and malignant lesions. ROC analysis was performed for assessing the values of parameters in discriminating benign and malignant breast lesions. Mann-Whitney U and Kruskal-Wallis H tests were used for the comparison of various prognostic factors or molecular subtypes.Spearman rank correlation analysis was used to explore the correlation of different prognostic factors and DKI and DWI parameters. Results The MK value of malignant group was higher than that of benign group,and the MD value and ADC value were lower than that of benign group (P<0.05). The area under the ROC for MK, MD and ADC were 0.897, 0.827 and 0.776, respectively. The area under the ROC was improved to 0.935 when three parameters were combined. The MK of ER positive group was higher than that of negative group (P<0.05). There was no significant difference of parameters among the other prognostic groups (all P>0.05). There was a low positive correlation between ER and MK (r= 0.417, P= 0.022). There was no correlation between the other prognostic factors and parameters (r=－0.086 to 0.313, all P>0.05). There was no significant difference in the MD, MK and ADC values among the four different subtypes of breast cancer (all P>0.05). Conclusions MK, MD and ADC values can be used to discriminate benign and malignant breast tumors, among which MK value has the best diagnostic performance. There is a certain correlation between DKI model parameters and prognostic factors.

Objective To evaluate the diagnostic efficacy of MRI diffusion kurtosis imaging (DKI) and quantitative dynamic contrast enhancement MRI (DCE-MRI) in benign and malignant breast lesions, and to explore the differential diagnosis ability for different pathological types and molecular subtype lesions. Methods Sixty four females were retrospectively enrolled in the study of MRI diffusion kurtosis imaging and quantitative dynamic contrast enhancement between November 20 and May 2017. All of them were confirmed to have benign or malignant lesions after surgical resection or puncture. All patients underwent axial T1WI, DKI and DCE-MRI examinations. The mean kurtosis (MK) and mean diffusivity (MD) values were calculated by the DKI model, and the hemodynamic parameters were obtained by quantitative dynamic contrast enhancement, including volume transfer constant (Ktrans), rate constant (Kep), extravascular extracellular space distribute volume per unit tissue volume (Ve) and blood volume fraction (Vp). Pathological analysis was performed to monitor the expression of estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER-2) and nuclear proliferation index Ki67. The breast cancer was divided into Luminal A type, Luminal B type, HER-2 positive and triple-negative 4 subtypes. The differences of DKI parameters and DCE-MRI parameters between benign and malignant breast lesions were compared using two independent samples t test (normal distribution and homogeneity of variance) or Mann-Whitney U test (skewed distribution or variance). ROC analysis was used to evaluate the value of DKI and DCE-MRI parameters in differential diagnosis of benign and malignant breast lesions with pathological results as the gold standard. The Mann-Whitney U test and Kruskal-Wallis H test were used to compare the differences of DKI and DCE-MRI parameters among different prognostic factors and molecular subtypes of breast cancer. Spearman rank correlation analysis was used to evaluate the correlation between DKI and DCE-MRI parameters and different prognostic factors. Results Sixty-four cases were single lesions, with breast cancer in 23 cases and 41 cases of benign lesions. In breast cancer, there were 9 cases of Luminal A type, 7 cases of Luminal B type, 3 cases of HER-2 positive type and 4 cases of triple negative type. The positive numbers of ER, PR and HER-2 were 14, 11 and 10 cases respectively. Nineteen cases showed high expression of Ki67, while 4 cases showed low expression. There were significant differences in MK, MD, Ktrans and Kep between benign and malignant lesions (P<0.05). However, there was no significant difference between Ve and Vp (P>0.05). The area under the ROC for the differential diagnosis of benign and malignant breast lesions were 0.897, 0.808, 0.844 and 0.842, respectively. The combined multi-parameter differential diagnosis improved the efficacy. Combined with the above four parameters, the area under the ROC was 0.950. The diagnosis Sensitivity, specificity and accuracy were 0.870, 0.951 and 0.922 respectively. The Ktrans and Vp values of patients with ER positive and ER negative, as well as Ve value of deferent lymph node status, were significantly different (P<0.05), but there was no significant difference between the other prognostic factors (P>0.05). There was a moderate positive correlation between ER and Ktrans and Vp values. There was a low positive correlation between lymph node status and Ve value (r= 0.6, 0.5 and 0.4, respectively, P<0.05). No correlation was found among other parameters and prognostic factors (P>0.05). There were no significant differences in DKI and DCE-MRI parameters among different subtypes of breast cancer patients (all P>0.05). Conclusion DKI combined with DCE-MRI can improve the differential diagnosis of breast lesions and some DCE-MRI parameters are related to prognostic factors.

Objective To validate and discuss the time response correction formula for four types of dosimeters (6150AD6 + 6150AD-b,FH40G + FHZ672E-10,451P ionization chamber and AT1123).Methods The ambient dose equivalent rates shown by survey meters were recorded separately when X-ray emission time was 500,200,100 and 50 ms.The corrected values were obtained by the formula of circuit having a capacitance C and asistance R in series.Results Therewas no correlation between the value measured by AT1123 dosimeter and the time of irradiation.The values by other three kinds of dosimeters obviously varied with the time of irradiation.Conclusions It is not required to make the time response correction for the measured value of ATl123 dosemeter,whereas the values measured by the other three dosimeters could be corrected by the time response correction formula.

Objective To increase the cumulative measurement level of 222 Rn and 220 Rn and ensure the accuracy and reliability of the measurement result . Methods By using improved 222 Rn-220 Rn discriminative detectors ( LD-P detectors) , the radon research group of National Institute for Radiological Protection Chinese Center for Disease Control and Prevention participated with the intercomparison organized by National Institute of Radiological Science ( NIRS) , Japan. Specifically, with the 222 Rn-220 Rn discriminative detectors being sent to Japan, the comparison was completed under different conditions in the 222 Rn chamber and 220 Rn chamber in NIRS. After exposure, the detectors were sent back to our laboratory for etching and analysis, and then measurement result were informed to NIRS. Finally, NIRS returned the exposure reference values of 222 Rn and 220 Rn to our laboratory. Results Under the conditions of high and low levels of 222 Rn, the relative percentage differences ( RPD ) between the measured values and the reference value provided by the NIRS were -12. 0％ and -11. 8％, respectively, while coefficients of variation ( COV) were 3. 0％ and 6. 2％, respectively. Under the conditions of high level and low levels of 220Rn, the relative percentage differences (RPD) between the measured value and the reference value provided by the NIRS were -0. 8％ and -8. 0％, respectively; coefficients of variation ( COV ) were 6. 7％ and 4. 5％, respectively. Conclusions This intercomparison result were categorized by NIRS ( PRD<10％) , with the satisfactory result of LD-P detectors available.

To ascertain the background and frequency of diagnostic medical X-ray procedures in China and provide the basis for regulatory oversight of such applications,a total of 557 medical institutions in 25 provinces or municipalities were surveyed by means of the optimally designed questionnaires and through stratified quota sampling.The numbers of procedures were calculated in terms of the type of procedures and the sex and age of examined patients.As a result,the frequencies of diagnostic X-ray procedures for 2016 in the country were derived using multiple linear regression analysis.The frequency of X-ray diagnosis in 10 provinces of China in 2016 was estimated to be 379-1 228 examinations per 1 000 population.Diagnostic X-ray applications have shown a rapid expansion in 2016 as compared with the period of "9th Five-Year Plan".It is very important to strengthen the regulation of medical diagnostic X-ray applications.