Objective To conduct Monte Carlo simulations on the microselectro-HDR¹⁹²Ir radiation source, investigate dose distributions under various conditions, and provide assistance in optimizing radiotherapy plans. Methods A microselectro-HDR¹⁹²Ir radiation source model was established based on the MCNP5 software. Theoretical calculation formulas were used to validate the simulation results. The dose distributions under different activities and positions were obtained through simulations using the MCNP5 transport program. By fitting the simulation data, the relationship between the safe distance for at-risk organs and treatment time was analyzed. Results As the distance from the origin increased in the X-direction, the distance required for the absorbed dose rate to decrease to half its original value increased, and the isodose lines became sparser. The shapes of the dose distribution diagrams under different activities were consistent, presenting concentric polygons and concentric circles at different distances. Under the condition of the same lethal dose, the difference in the safe distance between two organs increased with time; under different lethal dose conditions, the differences were not significant whether between similar organs or between different organs. Conclusion The Monte Carlo method can accurately describe the radiation field generated by the microselectro-HDR¹⁹²Ir radioactive source during high-dose-rate brachytherapy. Quantitative analysis of the radiation field will help optimize the radiotherapy plan.

Objective To conduct Monte Carlo simulations on the microselectro-HDR¹⁹²Ir radiation source, investigate dose distributions under various conditions, and provide assistance in optimizing radiotherapy plans. Methods A microselectro-HDR¹⁹²Ir radiation source model was established based on the MCNP5 software. Theoretical calculation formulas were used to validate the simulation results. The dose distributions under different activities and positions were obtained through simulations using the MCNP5 transport program. By fitting the simulation data, the relationship between the safe distance for at-risk organs and treatment time was analyzed. Results As the distance from the origin increased in the X-direction, the distance required for the absorbed dose rate to decrease to half its original value increased, and the isodose lines became sparser. The shapes of the dose distribution diagrams under different activities were consistent, presenting concentric polygons and concentric circles at different distances. Under the condition of the same lethal dose, the difference in the safe distance between two organs increased with time; under different lethal dose conditions, the differences were not significant whether between similar organs or between different organs. Conclusion The Monte Carlo method can accurately describe the radiation field generated by the microselectro-HDR¹⁹²Ir radioactive source during high-dose-rate brachytherapy. Quantitative analysis of the radiation field will help optimize the radiotherapy plan.

Objective To conduct Monte Carlo simulations on the microselectro-HDR¹⁹²Ir radiation source, investigate dose distributions under various conditions, and provide assistance in optimizing radiotherapy plans. Methods A microselectro-HDR¹⁹²Ir radiation source model was established based on the MCNP5 software. Theoretical calculation formulas were used to validate the simulation results. The dose distributions under different activities and positions were obtained through simulations using the MCNP5 transport program. By fitting the simulation data, the relationship between the safe distance for at-risk organs and treatment time was analyzed. Results As the distance from the origin increased in the X-direction, the distance required for the absorbed dose rate to decrease to half its original value increased, and the isodose lines became sparser. The shapes of the dose distribution diagrams under different activities were consistent, presenting concentric polygons and concentric circles at different distances. Under the condition of the same lethal dose, the difference in the safe distance between two organs increased with time; under different lethal dose conditions, the differences were not significant whether between similar organs or between different organs. Conclusion The Monte Carlo method can accurately describe the radiation field generated by the microselectro-HDR¹⁹²Ir radioactive source during high-dose-rate brachytherapy. Quantitative analysis of the radiation field will help optimize the radiotherapy plan.

Objective To compare H_p(3) calibration with a homemade (A) thermoluminescent dosimeter (TLD) and an imported (B) TLD in a standard X-ray RQR radiation field, to explore the different responses of A and B, and to provide foundation for the calibration of H_p(3). Methods A column mode was selected. H_p(3) calibration was performed using A and B in a standard X-ray RQR radiation field in the Secondary Standard Dosimetry Laboratory, National Institute for Radiological Protection, China Center for Disease Control and Prevention. Angle response, energy response, and linear response were calibrated with RQR4 (60 kV), RQR7 (90 kV), and RQR9 (120 kV), respectively. Results In terms of angle response, the calibration results of A were relatively high, while the calibration results of B were relatively low. In terms of energy response, the calibration results showed a similar pattern to angle response. In terms of linear response, the calibration results of both A and B were satisfactory. Conclusion Both A and B can be used for normal calibration of H_p(3) in a standard X-ray RQR radiation field. However, in actual monitoring, attention should be paid to the energy and angle response values of TLDs.