A method for designing an X-ray flatness filter for medical electron linac is developed. It is used in the optimization process in the electron beam radiation system. Monte Carlo simulation method is used and two exam...A method for designing an X-ray flatness filter for medical electron linac is developed. It is used in the optimization process in the electron beam radiation system. Monte Carlo simulation method is used and two examples of real radiation system optimization processes for China-made medical electron linac are provided： 15 MV X- ray system of BJ-20 linac, and 12 MeV electron system of BJ-14. Results are verified by using the traditional method.展开更多
Objective: This study aims to verify the feasibility of reducing the injected activity of18F-FDG by shortening the bed-dwell time based on body weight,and to design a weight-stratified radiation dose optimization syst...Objective: This study aims to verify the feasibility of reducing the injected activity of18F-FDG by shortening the bed-dwell time based on body weight,and to design a weight-stratified radiation dose optimization system to balance image quality and safety in adult tumor patients. Methods: A total of 100 tumor patients were selected and divided into a training set(70 cases) and a validation set(30 cases) in a 7∶3 ratio using the hold-out method. All patients received a standard injection of^(18)F-FDG at 5.3 MBq/kg and underwent whole-body scanning on a PHILIPS Ingenuity TF PET-CT system(VIP recording mode, 180 s/bed position for the training set). Six low-dose datasets were generated from the training set by simulating different bed-dwell times(60-160 s/bed position). The lesion detection concordance rate, subjective confidence, SUV_(max)error, and signal-to-noise ratio(SNR) were compared across different body weight subgroups. The validation set was scanned according to the optimization system derived from the training set to evaluate its effects on image quality, injected18F-FDG activity, and PET radiation dose. Results: For patients with body weight >70 kg, a bed-dwell time ≥120 s/bed position achieved a lesion detection rate of 92% and an SUV_(max)error <5%. For patients with body weight≤70 kg, a bed-dwell time ≥140 s/bed position was required to maintain comparable diagnostic accuracy, with a lesion detection concordance rate of 96.3% and an SUV_(max)error of 3.5%±1.2%. In the validation set, the mean effective dose(EDPET) was significantly lower than that in the pre-optimization training set for all body weight subgroups(P <0.05). Conclusion: The weight-stratified radiation dose optimization system based on shortened bed-dwell time can reduce the18F-FDG radiation dose for patients weighing >70 kg while maintaining lesion detection rates, thereby lowering the radiation exposure level in adult tumor patients.展开更多
We propose a method to determine the optimal power of the microwave resonance transition that simultaneously improves the signal-to-noise ratio and reduces line width based on saturation broadening theory and experime...We propose a method to determine the optimal power of the microwave resonance transition that simultaneously improves the signal-to-noise ratio and reduces line width based on saturation broadening theory and experiment. Saturation broadening spectra of the ground state hyperfine transition of trapped 199Hg＋ ions are measured and analyzed. The value of the optimal microwave power is obtained by using the proposed method and is verified. Rabi oscillations decay spectra of trapped 199Hg＋ ions are observed and the optimal microwave irradiation time for the maximum transition signal intensity is determined. This work will help to improve the short-term frequency stability of the mercury ion microwave frequency standard.展开更多
Objective: The purpose of this study was to compare the dose distribution and dose volume histogram (DVH) of the planning target volume (PTV) and organs at risk (OARs) among conventional radiation therapy (CR), three-...Objective: The purpose of this study was to compare the dose distribution and dose volume histogram (DVH) of the planning target volume (PTV) and organs at risk (OARs) among conventional radiation therapy (CR), three-dimensional conformal radiation therapy (3DCRT), two-step intensity-modulated radiation therapy (TS-IMRT) and direct machine parameter optimization intensity-modulated radiation therapy (DMPO-IMRT) after breast-conserving surgery. Methods: For each of 20 randomly chosen patients, 4 plans were designed using 4 irradiation techniques. The prescribed dose was 50 Gy/2 Gy/25 f, 95% of the planning target volume received this dose. The cumulated DVHs and 3D dose distributions of CR, 3DCRT, TS-IMRT and DMPO-IMRT plans were compared. Results: For the homogeneity indices, no statistically significant difference was observed among CR, 3DCRT, TS-IMRT and DMPO-IMRT while the difference of the conformality indices were statistically significant. With regard to the organs at risk, IMRT and 3DCRT showed a significantly fewer exposure dose to the ipsilateral lung than CR in the high-dose area while in the low-dose area, IMRT demonstrated a significant increase of exposure dose to ipsilateral lung, heart and contralateral breast compared with 3DCRT and CR. In addition, the monitor units (MUs) for DMPO-IMRT were approximately 26% more than those of TS-IMRT and the segments of the former were approximately 24% less than those of the latter. Conclusion: Compared with CR, 3DCRT and IMRT improved the homogeneity and conformity of PTV, reduced the irradiated volume of OARs in high dose area but IMRT increased the irradiated volume of OARs in low dose area. DMPO-IMRT plan has fewer delivery time but more MUs than TS-IMRT.展开更多
基金Supported by the National Natural Science Foundation of China (60672104,10675013)the Na-tional Basic Research Program of China ("973"Program)(2006CB705705)+1 种基金the 10th Five-Year Plan of the Ministry of Science and Technology of China(2001BA706B-05)the Joint Research Foundation of Beijing Municipal Commissionof Education~~
文摘A method for designing an X-ray flatness filter for medical electron linac is developed. It is used in the optimization process in the electron beam radiation system. Monte Carlo simulation method is used and two examples of real radiation system optimization processes for China-made medical electron linac are provided： 15 MV X- ray system of BJ-20 linac, and 12 MeV electron system of BJ-14. Results are verified by using the traditional method.
文摘Objective: This study aims to verify the feasibility of reducing the injected activity of18F-FDG by shortening the bed-dwell time based on body weight,and to design a weight-stratified radiation dose optimization system to balance image quality and safety in adult tumor patients. Methods: A total of 100 tumor patients were selected and divided into a training set(70 cases) and a validation set(30 cases) in a 7∶3 ratio using the hold-out method. All patients received a standard injection of^(18)F-FDG at 5.3 MBq/kg and underwent whole-body scanning on a PHILIPS Ingenuity TF PET-CT system(VIP recording mode, 180 s/bed position for the training set). Six low-dose datasets were generated from the training set by simulating different bed-dwell times(60-160 s/bed position). The lesion detection concordance rate, subjective confidence, SUV_(max)error, and signal-to-noise ratio(SNR) were compared across different body weight subgroups. The validation set was scanned according to the optimization system derived from the training set to evaluate its effects on image quality, injected18F-FDG activity, and PET radiation dose. Results: For patients with body weight >70 kg, a bed-dwell time ≥120 s/bed position achieved a lesion detection rate of 92% and an SUV_(max)error <5%. For patients with body weight≤70 kg, a bed-dwell time ≥140 s/bed position was required to maintain comparable diagnostic accuracy, with a lesion detection concordance rate of 96.3% and an SUV_(max)error of 3.5%±1.2%. In the validation set, the mean effective dose(EDPET) was significantly lower than that in the pre-optimization training set for all body weight subgroups(P <0.05). Conclusion: The weight-stratified radiation dose optimization system based on shortened bed-dwell time can reduce the18F-FDG radiation dose for patients weighing >70 kg while maintaining lesion detection rates, thereby lowering the radiation exposure level in adult tumor patients.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11074282 and 11474320
文摘We propose a method to determine the optimal power of the microwave resonance transition that simultaneously improves the signal-to-noise ratio and reduces line width based on saturation broadening theory and experiment. Saturation broadening spectra of the ground state hyperfine transition of trapped 199Hg＋ ions are measured and analyzed. The value of the optimal microwave power is obtained by using the proposed method and is verified. Rabi oscillations decay spectra of trapped 199Hg＋ ions are observed and the optimal microwave irradiation time for the maximum transition signal intensity is determined. This work will help to improve the short-term frequency stability of the mercury ion microwave frequency standard.
文摘Objective: The purpose of this study was to compare the dose distribution and dose volume histogram (DVH) of the planning target volume (PTV) and organs at risk (OARs) among conventional radiation therapy (CR), three-dimensional conformal radiation therapy (3DCRT), two-step intensity-modulated radiation therapy (TS-IMRT) and direct machine parameter optimization intensity-modulated radiation therapy (DMPO-IMRT) after breast-conserving surgery. Methods: For each of 20 randomly chosen patients, 4 plans were designed using 4 irradiation techniques. The prescribed dose was 50 Gy/2 Gy/25 f, 95% of the planning target volume received this dose. The cumulated DVHs and 3D dose distributions of CR, 3DCRT, TS-IMRT and DMPO-IMRT plans were compared. Results: For the homogeneity indices, no statistically significant difference was observed among CR, 3DCRT, TS-IMRT and DMPO-IMRT while the difference of the conformality indices were statistically significant. With regard to the organs at risk, IMRT and 3DCRT showed a significantly fewer exposure dose to the ipsilateral lung than CR in the high-dose area while in the low-dose area, IMRT demonstrated a significant increase of exposure dose to ipsilateral lung, heart and contralateral breast compared with 3DCRT and CR. In addition, the monitor units (MUs) for DMPO-IMRT were approximately 26% more than those of TS-IMRT and the segments of the former were approximately 24% less than those of the latter. Conclusion: Compared with CR, 3DCRT and IMRT improved the homogeneity and conformity of PTV, reduced the irradiated volume of OARs in high dose area but IMRT increased the irradiated volume of OARs in low dose area. DMPO-IMRT plan has fewer delivery time but more MUs than TS-IMRT.
