ABSTRACT
Objective Based on the lanthanum bromide scintillator detector, the calculation method of G(E) function was developed to measure the air absorbed dose rate. Methods Firstly, the gamma energy spectrumof the lanthanum bromide detector were simulated and the response functions with different energies were determined with Monte Carlo simulation method. Then, the G(E) function was calculated by the least square method. Finally, the air absorbed dose rate measured by the lanthanum bromide detector using G(E) function conversion method was compared with the theoretical calculation value based on the point source experiments. Results The experimental verification results showed that the relative deviation between thecalculated value with G(E) function and the theoretical calculation value wasmostly controlled within ± 6%, which verified the accuracy of G(E) function. Conclusion The results showed that the method of G(E) function could be applied to calculate the gamma radiation dose rate based on the in-situ the gamma spectrum with LaBr3 detector.
ABSTRACT
Objective To study the method of dose reconstruction in human body under the photon external radiation accident condition,and to verify the accuracy of the method for the local dose distribution.Methods Based on the open source Monte Carlo tool kit Geant 4 and using the human voxel phantom recommended by ICRP Publication 103,the dose reconstruction method under the condition of external radiation accident was studied to evaluate the average absorbed dose,organ absorbed dose and local dose distribution.To validate the code,several irradiation experiments were implemented in some standard radiation fields by putting TLDs in the tissue equivalent physical phantom ART.A voxel phantom was used to reconstruct the radiation doses,which was created based on the CT scan image of the ART phantom with resolution of 1.57 mm× 1.57 mm× 10.00 mm.The result of experiment were compared with those of dose reconstruction simulation.Results The relative uncertainty of the measured values was 10.9％.The relative uncertainty of the dose reconstruction simulation values was 7.10％ at the non-tissueinterface area and 16.6％ at the tissue-interface area.For 451 measuring points,the average of the simulated value divided by the measured value was 0.972,with the standard deviation of 0.083 8.In the range of 0.95-1.05,0.90-1.10 and 0.80-1.20,and the proportions were 49.2％,79.4％ and 96.4％,respectively.Conclusions The method of Monte Carlo dose reconstruction based on human voxel phantom meets the accuracy requirement of actual uses both at the whole body or organ level and at the local dose distribution level.It can be used as a powerful tool for dose assessment of the exposed people in an external radiation accidents and provide support for diagnosis and treatment.
ABSTRACT
Stroke is characterized by a group of acute cerebral vascular diseases which attack acutely with focal neurological deficits. Residual motor deficits often sojourn after stroke. Cortical stimulation, which is a technique developed many decades ago, has recently re-emerged as a promising method for researchers in their quest to causally probe cortical representations of sensorimotor and cognitive functions and to facilitate the treatment of various neuropsychiatric disorders. The article summarizes the research progress of cortical stimulation in the promotion of motor function recovery after stroke, the method of operation, the possible mechanisms and the prospect.