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Objective:To calculate the relative biological effectiveness (RBE) value of the released low-energy electrons in gadolinium neutron capture therapy ( 157GdNCT) based on microdosimetry. Methods:The Monte Carlo (MC) code Geant4-DNA package was used to simulate the energy deposition distribution and microdosimetry parameters of low-energy electrons released during gadolinium neutron capture treatment in different sensitive target volumes and physical models on track structures. On this basis, RBE value was obtained based on the microdosimetry kinetic model (MKM).Results:The low-energy electron RBE value was highly variable in different sensitive target volumes and decreases with increasing sensitive target volumes. With 6-nm-diameter sensitive target as reference, RBE value was 1.77 for 6-nm diameter, 1.53 for 10 nm diameter with percentage difference 13%, and 1.40 for 15-nm diameter with percentage difference of 21%, respectively. The effect of different Geant4-DNA physical models on the RBE of low-energy electrons was small. Using the RBE value of 1.53 for physical model option2 as reference, the RBE values of option6 and option7 were 1.49 and 1.52, respectively, with the percentage differences of 2.6% and 0.6%, respectively.Conclusions:The RBE values of low energy electrons released by 157GdNCT in different sensitive target volumes and physical models were calculated by MKM to be 1.40-1.77.
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The decreased occupational dose limit for eye lens has lead to an extensive focus on the eye lens dose monitoring and protection for occupational staff in interventional procedures.Based on the literature investigation of existing measurement and calculation results,the efficiency and influence factors of eye lens protective equipments for interventional staff are analyzed,and the suggestions for selection and use of them are provided.The main contribution to the eye lens dose to interventional staff is unshielded radiation which reaches the eyes directly.The key factors to inflence the efficiency of eye lens protective equipment is the geometric conditions such as structure,beam projection,position arrangement and operator postures,instead of lead equivalent thickness.Equipment of 0.5 mm lead equivalent thickness is enough to protect the eye lens of interventional staff.The combination of lead glasses and lead barrier can provide better protection in clinical practice.
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Objective To analyze the correlation between LC-MS/MS method and enzymatic cycling assay for determination of homocysteine concentration in human serum,and the application of two methods in the determination of homocysteine concentration.Methods Homocysteine concentrations of 63 serum samples were collected and determined by LC-MS/MS method and enzymatic cycling assay,respectively.The correlation between the concentrations by different methods was analyzed and evaluated.Results The concentrations were(19.11 ± 15.69) μmol/L by LC-MS/MS method and(16.95 ± 14.41) μmol/L by enzymatic cycling assay,the P value evaluated by paired-samples T test showed that there was statistical difference among the concentrations determined by two different methods (t =6.25,P ＜ 0.05).The conversion formula was YLC-MS/MS method =1.074Xenzymatic cycling assay + 0.892,R =0.987.Conclusion There is good correlation between LC-MS/MS method and enzymatic cycling assay for the determination of homocysteine concentration in serum,providing a theoretical basis for estimating the concentrations in the same serum sample by the two methods.
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In order to evaluate the pharmacokinetic profile of cefotiam hexetil hydrochloride tablet in Chinese healthy volunteers, a sensitive, specific and rapidprotein precipitation-liquid chromatography-tandem mass spectrometry method was developed and validated in human plasma. Chromatographic separation was achieved on a Waters Symmtry-C18 column (50 mm × 4. 6 mm, 5 μm), using a gradient mobile phase consisting of methanol and 1 mmol/ L ammonium acetate in water at a flow rate of 1. 0 mL/ min. Cefotiam and diazepam (internal standard) were detected without interference in the multiple reaction monitoring (MRM) mode with positive electrospray ionization. The calibration curve was linear from 5. 0 ng / mL to 5000 ng / mL (r>0. 99) with limit of quantitation of 5. 0 ng / mL. The assay met the published acceptance criteria. This rapid, sensitive and reproducible method was successfully applied to the pharmacokinetic study of cefotiam hexetil hydrochloride tablet in healthy Chinese volunteers and therefore provided a considerable mirror for quantification of other cephalosporins in human matrix.
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Objective To establish LC‐MS/MS method for the determination of fluoxetine in human plasma .Methods After protein precipitation of acetonitrile the plasma sample was separated on an Agilent XDB‐C18 column using acetonitrile‐1 mmol/L ammonium formate(containing 0 .1% formic acid) as mobile phase by gradient elution .Detection was carried out by multiple reac‐tion monitoring(MRM) on 3200QTRAP LC‐MS/MS system .Results The assay was linear over the range 0 .30 -50 .0 ng/mL with a lower limit of quantitation of 0 .30 ng/mL .Intra‐and inter‐day precision were less than 15% ,respectively .The relative devia‐tion was in the range -2 .80% -2 .09% .The recovery of fluoxetine was more than 98% with less matrix effects .The stabilities were good .Conclusion It could be a rapid ,sensitive ,selective and reliable method for the determination of fluoxetine in human plas‐ma for therapeutic drug monitoring and pharmacokinetics .