Objective:to study the effect of automatic tube current modulation on abdominal CT image quality and radiation dose. Methods: a total of 70 patients who underwent abdominal CT examination in our hospital from August 2...Objective:to study the effect of automatic tube current modulation on abdominal CT image quality and radiation dose. Methods: a total of 70 patients who underwent abdominal CT examination in our hospital from August 2019 to August 2020 were collected and divided into control group (35 cases) and study group (35 cases) according to the random number table. CT scan was performed in the control group according to the conventional parameters, while CT scan was performed in the research group using automatic tube current modulation technology. The CT image quality and radiation dose of patients in the two groups were compared. Results: the image quality of the study group was better than that of the control group (P < 0.05). When NI ≥8, the radiation dose in the study group was lower than that in the control group (P < 0.05). Conclusion Automatic tube current modulation technique can obtain better image quality in CT detection, and has significant significance in reducing radiation dose. It is worthy of affirmation, praise and application.展开更多
As use of the lowest acceptable radiation dose during routine diagnostic imaging is important, we determined the optimal tube current without degradation of low-contrast detectability on abdominal multi-detector row C...As use of the lowest acceptable radiation dose during routine diagnostic imaging is important, we determined the optimal tube current without degradation of low-contrast detectability on abdominal multi-detector row CT (MDCT). CT scanning was performed with a Catphan®?500 phantom. The optimal tube current was 300 mA on 64-MDCT and 160 mA on 8-MDCT, with a fixed voltage of 120 kV. Reduction of the radiation dose in abdominal CT scanning by lowering the tube current proved to be feasible.展开更多
Traveling Wave Tubes(TWTs) are widely used in the radar and communications system as RF power amplifiers. A highly sophisticated power supply is required by TWT. In order to meet the severe requirements of Traveling W...Traveling Wave Tubes(TWTs) are widely used in the radar and communications system as RF power amplifiers. A highly sophisticated power supply is required by TWT. In order to meet the severe requirements of Traveling Wave Tube Amplifier(TWTA), a novel two-stage topology high voltage converter for TWTA is proposed.The converter is based on Zero-Voltage Switching and Zero-Current Switching(ZVS/ZCS) resonant techniques. The high voltage converter operation principles are investigated and major features of the converter are discussed. The power switching mode of ZVS/ZCS is obtained. The experimental results show that the converter has good soft switching characteristics. Compared to the conventional hard switched Pulse Width Modulation(PWM) techniques, the high efficiency and low ripple of the converter for TWTA are realized. The efficiency of High Voltage Electronic Power Conditioners(HV-EPC) over 93.5% under the condition of 38~46 V input voltage and 260~300 W input power. The switching frequency of first-stage(preregulator) of HV-EPC is 89 k Hz and the switching frequency of second-stage(postregulator) is 44.5 k Hz. The highest output voltage of the HV-EPC is helix voltage which is about –6.8 kV. It is especially suitable for TWTA utilized in space satellite applications due to its high switching frequency and high power density.展开更多
目的·探讨自动管电流调制(automatic tube current modulation,ATCM)降低髋关节机器人CT辐射剂量的可行性,并系统评估其对图像质量的影响。方法·纳入南京鼓楼医院2021年11月至2024年10月进行髋机器人CT检查的患者共106例。采...目的·探讨自动管电流调制(automatic tube current modulation,ATCM)降低髋关节机器人CT辐射剂量的可行性,并系统评估其对图像质量的影响。方法·纳入南京鼓楼医院2021年11月至2024年10月进行髋机器人CT检查的患者共106例。采用随机分组设计,将全部受检者随机分为2组,A组(56例)使用ACTM扫描,B组(50例)使用部分固定管电流扫描(髋关节)。以容积CT剂量指数(volume CT dose index,CTDIvol)和辐射长度乘积(dose-length product,DLP)作为辐射剂量评估指标,以图像信噪比(signal-to-noise ratio,SNR)、对比信噪比(contrast signal to ratio,CNR)和客观噪声作为图像质量评估指标。比较2组患者的年龄、性别、体质量指数(body mass index,BMI)、扫描长度、CTDIvol、DLP、SNR、CNR、客观噪声、建模图像合格率。结果·2组患者的性别、年龄、BMI、扫描长度、图像建模合格率、SNR、CNR、客观噪声比较,差异均无统计学意义(均P>0.05)。A组的髋关节CTDIvol和DLP低于B组,差异有统计学意义(均P<0.001)。结论·使用ACTM技术进行髋关节机器人术前CT扫描,可显著降低辐射剂量,同时保证CT图像质量满足髋关节机器人术前建模需要。展开更多
文摘Objective:to study the effect of automatic tube current modulation on abdominal CT image quality and radiation dose. Methods: a total of 70 patients who underwent abdominal CT examination in our hospital from August 2019 to August 2020 were collected and divided into control group (35 cases) and study group (35 cases) according to the random number table. CT scan was performed in the control group according to the conventional parameters, while CT scan was performed in the research group using automatic tube current modulation technology. The CT image quality and radiation dose of patients in the two groups were compared. Results: the image quality of the study group was better than that of the control group (P < 0.05). When NI ≥8, the radiation dose in the study group was lower than that in the control group (P < 0.05). Conclusion Automatic tube current modulation technique can obtain better image quality in CT detection, and has significant significance in reducing radiation dose. It is worthy of affirmation, praise and application.
文摘As use of the lowest acceptable radiation dose during routine diagnostic imaging is important, we determined the optimal tube current without degradation of low-contrast detectability on abdominal multi-detector row CT (MDCT). CT scanning was performed with a Catphan®?500 phantom. The optimal tube current was 300 mA on 64-MDCT and 160 mA on 8-MDCT, with a fixed voltage of 120 kV. Reduction of the radiation dose in abdominal CT scanning by lowering the tube current proved to be feasible.
文摘Traveling Wave Tubes(TWTs) are widely used in the radar and communications system as RF power amplifiers. A highly sophisticated power supply is required by TWT. In order to meet the severe requirements of Traveling Wave Tube Amplifier(TWTA), a novel two-stage topology high voltage converter for TWTA is proposed.The converter is based on Zero-Voltage Switching and Zero-Current Switching(ZVS/ZCS) resonant techniques. The high voltage converter operation principles are investigated and major features of the converter are discussed. The power switching mode of ZVS/ZCS is obtained. The experimental results show that the converter has good soft switching characteristics. Compared to the conventional hard switched Pulse Width Modulation(PWM) techniques, the high efficiency and low ripple of the converter for TWTA are realized. The efficiency of High Voltage Electronic Power Conditioners(HV-EPC) over 93.5% under the condition of 38~46 V input voltage and 260~300 W input power. The switching frequency of first-stage(preregulator) of HV-EPC is 89 k Hz and the switching frequency of second-stage(postregulator) is 44.5 k Hz. The highest output voltage of the HV-EPC is helix voltage which is about –6.8 kV. It is especially suitable for TWTA utilized in space satellite applications due to its high switching frequency and high power density.
文摘目的·探讨自动管电流调制(automatic tube current modulation,ATCM)降低髋关节机器人CT辐射剂量的可行性,并系统评估其对图像质量的影响。方法·纳入南京鼓楼医院2021年11月至2024年10月进行髋机器人CT检查的患者共106例。采用随机分组设计,将全部受检者随机分为2组,A组(56例)使用ACTM扫描,B组(50例)使用部分固定管电流扫描(髋关节)。以容积CT剂量指数(volume CT dose index,CTDIvol)和辐射长度乘积(dose-length product,DLP)作为辐射剂量评估指标,以图像信噪比(signal-to-noise ratio,SNR)、对比信噪比(contrast signal to ratio,CNR)和客观噪声作为图像质量评估指标。比较2组患者的年龄、性别、体质量指数(body mass index,BMI)、扫描长度、CTDIvol、DLP、SNR、CNR、客观噪声、建模图像合格率。结果·2组患者的性别、年龄、BMI、扫描长度、图像建模合格率、SNR、CNR、客观噪声比较,差异均无统计学意义(均P>0.05)。A组的髋关节CTDIvol和DLP低于B组,差异有统计学意义(均P<0.001)。结论·使用ACTM技术进行髋关节机器人术前CT扫描,可显著降低辐射剂量,同时保证CT图像质量满足髋关节机器人术前建模需要。
