Dose estimation and quality control in computed tomography (CT) scanners are useful in controlling the dose of radiation given to patients while tests are carried out. The study was performed in a 16-slice Computed To...Dose estimation and quality control in computed tomography (CT) scanners are useful in controlling the dose of radiation given to patients while tests are carried out. The study was performed in a 16-slice Computed Tomography (CT) system of LightSpeed RT16 Xtra CT scanner. Quality control was done using a vendor-provided QA Phantom, and the six aspects of image quality were measured. For CT dosimetry, Computed Tomography Dose index volume (CTDIvol) was performed using Computed Tomography Dose Index (CTDI) Phantom. CTDI Phantom consists of three parts: Pediatric Head, Adult Head, and Adult Body Phantom. A 10 cm long pencil ion chamber DCT-10 was used to measure the dose at different positions inside the CTDI Phantom. Data were collected using MagicMax Universal software. For dose estimation of the CTDIvol Report of AAPM Task Group, 96 and 111 formalisms were used. For Pediatric Head, Adult Head, and Adult Body Phantom the measured CIDIvol was 61.04 mGy, 48.11 mGy, and 18.08 mGy respectively. The study has shown deviations of 7%, 15%, and 19% between estimated and console-displayed doses for Pediatric Head, Adult Head, and Adult Body scan techniques respectively. The six aspects of image quality measured by QA Phantom were found to be compatible with the specifications of the machine and CTDIvol measured by CTDI Phantom were found within a tolerance limit of ±20%. Hence, the QC and dosimetry of the mentioned machine are within the limit.展开更多
为满足新一代海洋水色观测卫星载荷成像质量提升的需求,针对影响成像质量的关键因素,如信噪比(signal-to-noise ratio,SNR)、扫描机构稳定性及杂光抑制等,采取优化设计和控制措施。通过增大入光口径、增加扫描像元数量和积分时间、优化...为满足新一代海洋水色观测卫星载荷成像质量提升的需求,针对影响成像质量的关键因素,如信噪比(signal-to-noise ratio,SNR)、扫描机构稳定性及杂光抑制等,采取优化设计和控制措施。通过增大入光口径、增加扫描像元数量和积分时间、优化光路及调整时间延迟积分(time-delay integration,TDI)级数和增益等级等措施,提高了SNR;通过匀速扫描、缓启/缓停设计及提高测角分辨率等措施,增强了扫描机构稳定性的线性度;采用遮光罩、挡光板等组合结构抑制杂光;通过实时控制Y方向偏航修正偏流角。测试结果表明:水色水温扫描仪(Chinese ocean color and temperature scanner,COCTS)的SNR最高可达1760,扫描机构线性度为0.24%,杂光系数≤1%;海岸带成像仪(coastal zone imager,CZI)多光谱谱段的动态调制传递函数(modulation transfer function,MTF)≥0.20、全色谱段的MTF≥0.15。各类载荷在轨图像质量优良,为海洋资源开发、环境监测等提供了高质量数据支撑。展开更多
To expand scanning area and attack range without changing the inner structure of intelligent warhead, a new arrangement mode of the scanner for intelligent mine is proposed. The required coordinate systems are es...To expand scanning area and attack range without changing the inner structure of intelligent warhead, a new arrangement mode of the scanner for intelligent mine is proposed. The required coordinate systems are established firstly on the basis of advanced dynamics principle. and the exterior ballistics equations are deduced. Then the equations of scanning trails are established by the method of space analytic geometry. To get the scanning trails. the differential equations are transformed into discrete simulation model using the algorithm of fourth order Runge-Kutta and then are simulated using Matlab. Compared with the scanning trails obtained by the traditional layout of scanner, the scanning trails obtained by the proposed layout of scanner has larger horizontal range of scanning circle and bigger trarget acquisition probability. Therefore, the new arrangement mode of the scanner for intelligent mine can increase attack range.展开更多
文摘Dose estimation and quality control in computed tomography (CT) scanners are useful in controlling the dose of radiation given to patients while tests are carried out. The study was performed in a 16-slice Computed Tomography (CT) system of LightSpeed RT16 Xtra CT scanner. Quality control was done using a vendor-provided QA Phantom, and the six aspects of image quality were measured. For CT dosimetry, Computed Tomography Dose index volume (CTDIvol) was performed using Computed Tomography Dose Index (CTDI) Phantom. CTDI Phantom consists of three parts: Pediatric Head, Adult Head, and Adult Body Phantom. A 10 cm long pencil ion chamber DCT-10 was used to measure the dose at different positions inside the CTDI Phantom. Data were collected using MagicMax Universal software. For dose estimation of the CTDIvol Report of AAPM Task Group, 96 and 111 formalisms were used. For Pediatric Head, Adult Head, and Adult Body Phantom the measured CIDIvol was 61.04 mGy, 48.11 mGy, and 18.08 mGy respectively. The study has shown deviations of 7%, 15%, and 19% between estimated and console-displayed doses for Pediatric Head, Adult Head, and Adult Body scan techniques respectively. The six aspects of image quality measured by QA Phantom were found to be compatible with the specifications of the machine and CTDIvol measured by CTDI Phantom were found within a tolerance limit of ±20%. Hence, the QC and dosimetry of the mentioned machine are within the limit.
文摘为满足新一代海洋水色观测卫星载荷成像质量提升的需求,针对影响成像质量的关键因素,如信噪比(signal-to-noise ratio,SNR)、扫描机构稳定性及杂光抑制等,采取优化设计和控制措施。通过增大入光口径、增加扫描像元数量和积分时间、优化光路及调整时间延迟积分(time-delay integration,TDI)级数和增益等级等措施,提高了SNR;通过匀速扫描、缓启/缓停设计及提高测角分辨率等措施,增强了扫描机构稳定性的线性度;采用遮光罩、挡光板等组合结构抑制杂光;通过实时控制Y方向偏航修正偏流角。测试结果表明:水色水温扫描仪(Chinese ocean color and temperature scanner,COCTS)的SNR最高可达1760,扫描机构线性度为0.24%,杂光系数≤1%;海岸带成像仪(coastal zone imager,CZI)多光谱谱段的动态调制传递函数(modulation transfer function,MTF)≥0.20、全色谱段的MTF≥0.15。各类载荷在轨图像质量优良,为海洋资源开发、环境监测等提供了高质量数据支撑。
文摘To expand scanning area and attack range without changing the inner structure of intelligent warhead, a new arrangement mode of the scanner for intelligent mine is proposed. The required coordinate systems are established firstly on the basis of advanced dynamics principle. and the exterior ballistics equations are deduced. Then the equations of scanning trails are established by the method of space analytic geometry. To get the scanning trails. the differential equations are transformed into discrete simulation model using the algorithm of fourth order Runge-Kutta and then are simulated using Matlab. Compared with the scanning trails obtained by the traditional layout of scanner, the scanning trails obtained by the proposed layout of scanner has larger horizontal range of scanning circle and bigger trarget acquisition probability. Therefore, the new arrangement mode of the scanner for intelligent mine can increase attack range.
