ABSTRACT
Objective To explore the Monte Carlo calculation methods for the absolute dose calibration and output factor of 6 MV flattening-filter ( FF) and flattening-filter free ( FFF) photon beams based on TrueBeam accelerator .Methods The BEAMnrc code was used to model the LINAC head of FF and FFF modes.The BEAM_up covers the components from the target to the monitor chamber , and BEAM_down includes the structures beneath the chamber , the dose deposit to the monitor chamber contributed by the incidence electrons and scattered particles from the secondary collimators were calculated respectively .The incidence electron-induced dose at certain depths on the central axis were simulated by means of the DOSXYZnrc code .By means of dose calibration equation , the calibration factor for the standard field (10 cm ×10 cm) and the output factors for various fields (1 cm ×1 cm-40 cm ×40 cm) were computed respectively .Results For the 6 MV FF and FFF beams under the standard 10 cm ×10 cm field, 1 MU equals to 7.747 ×1013 ±3.099 ×1011 and 3.248 ×1013 ±1.624 ×1011 electrons to the target , respectively , which deposited 21.53 and 35.01 cGy to the monitor chamber of the virtual accelerator respectively .The difference between the simulated and calculated output factors were 0.72%±1.4%and 0.56%±0.78%for FF and FFF , respectively .Conclusions The model generated and measured output factors agree well , indicating the good accuracy of the dose calculation by the model , which would provides basis for further clinical dosimetric studies .
ABSTRACT
OBJECTIVE:To discuss the correlation between multidrug resistance gene (MDR1) polymorphisms and plasma concentration of risperidone,9-hydroxyrisperidone and total active substance in Han patients with schizophrenia. METHODS:78 Han inpatients with schizophrenia in Mental Health Institute of Second Xiangya Hospital of Central South University from Dec. 2011 to Jan. 2013 were selected,LC-MS/MS was conducted to determine the plasma concentration of risperidone,9-hydroxyrisperi-done and total active substance,PCR-LDR was adopted to determine the genotyping of C1236T,G2677T and C3435T of patients, and one-way ANOVA was used to detect the correlation between C1236T,G2677T and C3435T polymorphisms and plasma concen-tration/dose calibration ratio (C/D) value of risperidone,9-hydroxyrisperidone and total active substance. RESULTS:The average plasma concentrations of risperidone,9-hydroxyrisperidone and total active substance for 78 patients were(13.58±8.31),(25.62± 15.52)and(39.24±25.76)ng/ml,respectively;the distribution frequencies of C1236T,G2677T and C3435T met the Hardy-Wein-berg equilibrium(P>0.05);the risperidone C/D value of patients with C12367T CT and TT genotype were higher than those with CC genotype,risperidone and total active substance C/D values of patients with G2677T TT genotype were higher than those with GG genotype,the differences were statistically significant (P0.05). CONCLUSIONS:The MDR1 C1236T and G2677T polymorphisms are associated with plasma concentration of risperidone and total active substance in Han patients with schizophrenia.
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Objective To calibrate the dose of 12MeV high-energy electron for Siemens MD7745 medical linear accelerator.Methods The international protocols,contents and technical standards were expatiated.Some existing problems in dose calibration of high-energy electron were analyzed.Results The working precision met the requirement of quality assurance in radiotherapy by WHO.Conclusion In order to improve the therapeutic effect,the dose must be calibrated,and the error in dose calibration of high-energy electron should be reduced to the lowest.
ABSTRACT
The procedures for the calculation and measurement and calibration of output dose of the Siemens primus E accelerator with IAEA regulation are introduced to probe an accurate,rapid and effective method.The parameter value of measurement is determined according to IAEA regulations and absorbed dose calculation formal is briefed to the form that the reading of instrument multiplies exposure calibration coefficient Nx and Air temperature,pressure and humidity effects Ktp and cumulative correction factor Cf the precision of accelerator conform to the standard of QA&QC by the measurement and calibration of the Hospital Primus E accelerator in output dose.The methods of measurement and calibration can be used for the determination of output dose in precise radiotherapy of digital medical linear accelerator and clinical treatment.