Objective:To investigate the radiation field distribution characteristics in a 9 MeV electron FLASH (e-FLASH) linear accelerator treatment room.Methods:The Geant4 Monte Carlo program was employed for physical simulating of the radiation field distribution inside and outside the treatment room under a single-beam delivery condition with a total dose of 50 Gy at the reference point and a dose rate of 250 Gy/s. High-sensitivity radiation detectors (AT1123) were used to validate the measurements at key points.Results:The dose rate at the reference point was approximately 9×10 11 μSv/h. Due to the scattering and shielding effects, the deviation of the attenuation rate from the inverse-square law was observed and the isodose lines exhibited spatial drift. Measured dose rates at key points showed good agreement with the simulation result, with a maximum deviation within 30%. Conclusions:The complex radiation field distribution can be effectively simulated using Geant4 in an e-FLASH treatment room. This indicated the Geant4 is not only applicable for the shielding calculations in e-FLASH radiotherapy facilities, but also for the design optimization through, reduction of trial-and-error iterations and engineering costs.

Objective:To investigate the radiation field distribution characteristics in a 9 MeV electron FLASH (e-FLASH) linear accelerator treatment room.Methods:The Geant4 Monte Carlo program was employed for physical simulating of the radiation field distribution inside and outside the treatment room under a single-beam delivery condition with a total dose of 50 Gy at the reference point and a dose rate of 250 Gy/s. High-sensitivity radiation detectors (AT1123) were used to validate the measurements at key points.Results:The dose rate at the reference point was approximately 9×10 11 μSv/h. Due to the scattering and shielding effects, the deviation of the attenuation rate from the inverse-square law was observed and the isodose lines exhibited spatial drift. Measured dose rates at key points showed good agreement with the simulation result, with a maximum deviation within 30%. Conclusions:The complex radiation field distribution can be effectively simulated using Geant4 in an e-FLASH treatment room. This indicated the Geant4 is not only applicable for the shielding calculations in e-FLASH radiotherapy facilities, but also for the design optimization through, reduction of trial-and-error iterations and engineering costs.

Objective:To measure the beam stability of the electron FLASH radiotherapy accelerator developed by the Institute of Applied Electronics of Chinese Academy of Engineering Physics and to evaluate the performance of scintillator, fast current sensor (FCT) and graphite under the electron FLASH beam.Methods:Each continuous beam exit deviation and each pulse deviation at the electron FLASH radiotherapy accelerator in the same working state were measured. The correlation among three monitors and the measured dose of the accelerator at different electron beam energy (controlled by changing the charging voltage) and different beam pulse numbers were compared, which were validated by a Monte Carlo simulation procedure.Results:At the first high pressure, the first 10 scintillators and FCT signals were relatively large, approximately 2% deviation compared with the average value of 400 pulses. Among 40 beam outflows, the deviation between each pulse was within ±5%. In the accelerator steady state, each beam outflow deviation was within ±1%. Both simulated and measured values showed that the monitor could not be used for dose monitoring at different electron beam energy. However, when the energy was the same, only the number of beam pulses was changed, and linear relationship was observed between the number of the three monitors and the dose measured by the film (all R 2 > 0.999). Conclusions:The beam deviation of each beam outflow of this electron FLASH accelerator is within ±1%. Under the stability of the accelerator beam, the scintillator, FCT and graphite can meet the dose monitoring of the target area, which can provide reference for dose monitoring for subsequent biological experiments.

Objective To investigate the therapeutic procedures,indications and efficacy of breast-conserving therapy (BCT). Methods BCT was carried out in 148 patients with breast carcinoma in this hospital from January 1996 to October 2003.There were 5 patients in stage 0,85 patients in stage Ⅰ,55 patients in stage Ⅱ,and 3 patients in stage Ⅲ.The surgical treatment was quadrantectomy or local wide excision of tumor,combined with axillary lymph node dissection.Routine adjuvant irradiation,chemotherapy and hormone therapy were given postoperatively. Results Pathological examinations of breast specimens found no positive margins.Follow-up observations for a median of 54 months (range,2 ～ 84 months) revealed a local recurrence rate of 2 7% ( 4/148 ;3 patients in breast and 1 patient in axillary fossa).Distant metastasis occurred in 5 patients (3 4%) and 3 of them died.Sites of metastasis included lung,liver,meninges and bone.The duration from surgery to distant metastasis was 6 ～ 43 months.Evaluation of cosmetic results in 108 patients who had received BCT for at least 12 months showed that good outcomes were achieved in 32 4% of the patients (35/108),fair outcomes,in 49 1% of the patients (53/108),and poor,in 18 5% (20/108). Conclusions For patients with early stage breast carcinoma,and part of those with local advanced breast cancer who have received neoadjuvant chemotherapy and gotten downstaging effects,the effects of BCT is satisfactory.Standard excision,postoperative irradiation and systemic combination treatment are crucial to BCT.Most patients receiving BCT have good cosmetic results.

12 months postoperatively,and excellent results were obtained in 16.0% of the patients((4/25)),good in 40.0%(10/25),and poor in 44.0%(11/25). Conclusions For patients with locally advanced breast cancer previously treated with downstaging neoadjuvant chemotherapy,breast-conserving therapy offers satisfactory results.Strict adherence to technique and use of postoperative irradiation and systemic therapy are crucial to breast-conserving therapy.

Objective The aim of this study is to investigate STAT3 expression and the relationship between protein levels of STAT3 and clinicopathological parameters together with preoperative chemotherapy in human breast cancer. Methods Samples were obtained from 51 patients with breast carcinoma in which 7 patients had received preoperative chemotherapy. Western blot was used to measure the protein expression in tissue and SK-BR-3 cell line. MTT method was used to evaluate the proliferation. Cell-cycle and apoptosis were quantified by flow cytometry. Results STAT3 protein levels increased in breast cancer tissues compared with adjacent normal tissues(t=5.540,P