Purpose: To test the concept of Statistical Process Control (SPC) as a Quality Assurance (QA) procedure for dose verifications in external beam radiation therapy in conventional and 3D Conformal Radiotherapy (3D-CRT) ...Purpose: To test the concept of Statistical Process Control (SPC) as a Quality Assurance (QA) procedure for dose verifications in external beam radiation therapy in conventional and 3D Conformal Radiotherapy (3D-CRT) treatment of cervical cancer. Materials and Methods: A study of QA verification of target doses of 198 cervical cancer patients undergoing External Beam Radiotherapy (EBRT) treatments at two different cancer treatment centers in Kenya was conducted. The target doses were determined from measured entrance doses by the diode in vivo dosimetry. Process Behavior Charts (PBC) developed by SPC were applied for setting Action Thresholds (AT) on the target doses. The AT set was then proposed as QA limits for acceptance or rejection of verified target doses overtime of the EBRT process. Result and Discussion: Target doses for the 198 patients were calculated and SPC applied to test whether the action limits set by the Process Behavior Charts could be applied as QA for verified doses in EBRT. Results for the two sub-groups of n = 3 and n = 4 that were tested produced action thresholds which are within clinical dose specifications for both conventional AP/PA and 3D-CRT EBRT treatment techniques for cervical cancer. Conclusion: Action thresholds set by SPC were within the clinical dose specification of ±5% uncertainty for both conventional AP/PA and 3D-CRT EBRT treatment techniques for cervical cancer. So the concept of SPC could be applied in setting QA action limits for dose verifications in EBRT.展开更多
In order to accommodate electron beam to the brazing of the joints with various curve shapes and the brazing of thermo sensitive materials, the method of electron beam scanning and brazing temperature control was deve...In order to accommodate electron beam to the brazing of the joints with various curve shapes and the brazing of thermo sensitive materials, the method of electron beam scanning and brazing temperature control was developed, in which electron beam was controlled to scan according to predefined scanning track, and the actual temperature rising velocity of the brazed seam was lim- ited in an allowed scope by detecting the brazed seam temperature, calculating the temperature rising velocity and adjusting the beam current during the brazing process; in addition, through the setting of the highest allowed temperature, the actual temperature of the brazed seam could be controlled not exceeding the threshold set value, and these two methods could be employed alone or jointly. It is shown that high precision temperature control in electron beam brazing could be realized and the productivity be increased by the proposed method.展开更多
文摘Purpose: To test the concept of Statistical Process Control (SPC) as a Quality Assurance (QA) procedure for dose verifications in external beam radiation therapy in conventional and 3D Conformal Radiotherapy (3D-CRT) treatment of cervical cancer. Materials and Methods: A study of QA verification of target doses of 198 cervical cancer patients undergoing External Beam Radiotherapy (EBRT) treatments at two different cancer treatment centers in Kenya was conducted. The target doses were determined from measured entrance doses by the diode in vivo dosimetry. Process Behavior Charts (PBC) developed by SPC were applied for setting Action Thresholds (AT) on the target doses. The AT set was then proposed as QA limits for acceptance or rejection of verified target doses overtime of the EBRT process. Result and Discussion: Target doses for the 198 patients were calculated and SPC applied to test whether the action limits set by the Process Behavior Charts could be applied as QA for verified doses in EBRT. Results for the two sub-groups of n = 3 and n = 4 that were tested produced action thresholds which are within clinical dose specifications for both conventional AP/PA and 3D-CRT EBRT treatment techniques for cervical cancer. Conclusion: Action thresholds set by SPC were within the clinical dose specification of ±5% uncertainty for both conventional AP/PA and 3D-CRT EBRT treatment techniques for cervical cancer. So the concept of SPC could be applied in setting QA action limits for dose verifications in EBRT.
文摘In order to accommodate electron beam to the brazing of the joints with various curve shapes and the brazing of thermo sensitive materials, the method of electron beam scanning and brazing temperature control was developed, in which electron beam was controlled to scan according to predefined scanning track, and the actual temperature rising velocity of the brazed seam was lim- ited in an allowed scope by detecting the brazed seam temperature, calculating the temperature rising velocity and adjusting the beam current during the brazing process; in addition, through the setting of the highest allowed temperature, the actual temperature of the brazed seam could be controlled not exceeding the threshold set value, and these two methods could be employed alone or jointly. It is shown that high precision temperature control in electron beam brazing could be realized and the productivity be increased by the proposed method.
