ABSTRACT
Objective:To study the dose response of two-dimensional ionization chamber matrix detectors under IMRT fields irradiation at different gantry angles and different directions.Methods:After the dose calibration of the medical accelerator and the two-dimensional ionization chamber matrix detector respectively, the solid water phantom was used to cover the upper part of the two-dimensional ionization chamber matrix detector. Adjusting the thickness of the solid water, the effective distances between the effective measuring center of the two-dimensional ionization chamber matrix detector and the incident point of the central axis of the radiation on the surface of the phantom was always controlled at 5 cm. Four locations with 0、45、90 and 135 degrees of the long axis of the treatment bed were selected, and each location was irradiated by IMRT fields at different frame angle of 60°, 45°, 30°, 15°, 0°, -15°, -30°, -45° and -60°, respectively.Results:The dose deviation of the medical accelerator was less than 0.18% in the range of different rack angles. The directional response deviation of the two-dimensional ionization chamber matrix detector was less than 0.63%, and the measurement deviation of each probe of the two-dimensional ionization chamber matrix detector to its center probe was less than 0.50%.Conclusions:The two-dimensional ionization chamber matrix detector has good directional response and it is a useful tool for developing intensity-modulated radiotherapy technology. The method proposed in this study can provide a basic basis for the relevant medical accelerator metrology departments to formulate corresponding quality control test specifications.
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Objective To observe the relationship between expression changes of γH2AX and the radiosensitivity of lung cancer cells in vitro. Methods The radiosensitivity of lung cancer cell lines A549 and SBC-3 was measured by clone forming assay. The DSBs damage of lung cancer cell lines A549 and SBC-3 was determined by Western blot assay. Re-sults The clone forming rates of lung cancer cell lines A549 and SBC-3 were gradually decreased with the increased radia-tion dose.γH2AX expression was related to the cell radiosensitivity 1 hour and 6 hours after radiated. Conclusion The phosphorylated histoneγH2AX is a powerful tool to monitor DNA DSBs and to predict the radiosensitivity in lung cancer ra-diotherapy.
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Nasal NK/T cell lymphoma is a rare and distinct type of extranodal Non-Hodgkin' s lymphoma. Current study has proved that Radiotherapy is the most effective treatment method in the early stage nasal NK/T cell lymphoma, but there is no universal standard for concrete radiotherapy modality, such as the radiation target, the radiation dose and preventive neck radiation. Most studies have proved that radiotherapy of extended field and higher dose achieved good effect in early stage nasal NK/T cell lymphoma.And the studies also do not suggested preventive neck radiation in local stage patients, but it need further study in the extensive stage patients.
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Objective To evaluate the curative effect of nasal non-Hodgkin lymphoma(N-NHL) by four types of therapy such as pure chemotherapy, pure radiotherapy, chemotherapy combined with radiotherapy, and APBSCT combined with TBI. Methods One hundred and thirty five patients with nasal NHL were treated between 1980 and 2000. All patients received radiotherapy alone or chemotherapy alone or radiotherapy combined with radiotherapy or TBI combined with APBSCT. The median radiation dose to the nasal cavity was 56.0 Gy with a range of 35.2 to 75.5 Gy. Six patients received TBI combined APBSCT. The TBI dose was 8 Gy. Two patients received 30 Gy in nasal of the six patients. The chemotherapy regimen consisted of 2-6 cycles of COP, COPP, COMP, CHOP, COBDP. Results The local control rate and 5-year survival rate of the four groups of pure chemotherapy, pure radiotherapy, combined chemotherapy and radiotherapy and APBSCT combined with TBI were 12 %, 69 %, 76 %, 83 % and 9 %, 52 %, 63 %, 83 %. For the four groups, the best is APBSCT, then combined chemotherapy and radiotherapy group ,then pure radiotherapy, the last is pure chemotherapy. There is significant difference between the four groups(P