Design of the Space Camera Protection System during Launch Process

The project supported the Nuclear Regulatory Commission (NRC) in identifying and evaluating the regulatory implications concerning the control and protection systems proposed for use in the Department of Energy's (DOE) Next-Generation Nuclear Plant (NGNP). The NGNP, using modular high-temperature gas-cooled reactor (HTGR) technology, is to provide commercial industries with electricity and high-temperature process heat for industrial processes such as hydrogen production. Process heat temperatures range from 700 to 950 C, and for the upper range of these operation temperatures, the modular HTGR is sometimes referred to as the Very High Temperature Reactor or VHTR. Initial NGNP designs are for operation in the lower temperature range. The defining safety characteristic of the modular HTGR is that its primary defense against serious accidents is to be achieved through its inherent properties of the fuel and core. Because of its strong negative temperature coefficient of reactivity and the capability of the fuel to withstand high temperatures, fast-acting active safety systems or prompt operator actions should not be required to prevent significant fuel failure and fission product release. The plant is designed such that its inherent features should provide adequate protection despite operational errors or equipment failure. Figure 1 shows an example modular HTGR layout (prismatic core version), where its inlet coolant enters the reactor vessel at the bottom, traversing up the sides to the top plenum, down-flow through an annular core, and exiting from the lower plenum (hot duct). This research provided NRC staff with (a) insights and knowledge about the control and protection systems for the NGNP and VHTR, (b) information on the technologies/approaches under consideration for use in the reactor and process heat applications, (c) guidelines for the design of highly integrated control rooms, (d) consideration for modeling of control and protection system designs for VHTR, and (e) input for developing the bases for possible new regulatory guidance to assist in the review of an NGNP license application. This NRC project also evaluated reactor and process heat application plant simulation models employed in the protection and control system designs for various plant operational modes and accidents, including providing information about the models themselves, and the appropriateness of the application of the models for control and protection system studies. A companion project for the NRC focused on the potential for new instrumentation that would be unique to modular HTGRs, as compared to light-water reactors (LWRs), due to both the higher temperature ranges and the inherent safety features.

Space cameras play a pivotal role in various fields, such as astronomical exploration. When operating in orbit, these cameras encounter the relative motion between the target and the camera during the exposure, resulting in image motion, which affects the imaging quality. Therefore, it is necessary to compensate for this image motion. This paper investigates the in-orbit image motion compensation (IMC) method for space cameras with a long integration time based on a two-axis pointing platform. Firstly, the mechanical design of the camera is introduced. Secondly, the in-orbit IMC model for the camera is analyzed, and the angular motion needed for compensating for the image motion by the two-axis pointing platform are derived. Factors influencing the compensation accuracy are also analyzed. The effectiveness of the IMC model is verified through simulations. Finally, the in-orbit experimental results indicate that the energy concentration of the target star images obtained exceeded 70%, demonstrating excellent performance in space cameras and effectively enhancing imaging quality using IMC technology.

The influence of jitter on the interface between space camera and satellite platform may cause the camera structural distortion, which will change ideal assembly and adjustment relationship of optical system, and affect the imaging quality. An integrated model of a high resolution space camera comprising reaction wheel assemblies disturbance which induced the largest jitter of spacecraft, structures and optics systems was developed in order to predict the expected dynamic performance of the camera in terms of MTF descending and image motion. The process as currently implemented uses Pro/Engineer for design, PATRAN and Hypermesh for model building and results visualization, NASTRAN for structural analysis, and Code V for optical analysis. A translator was developed in MATLAB to transfer PATRAN results to Code V optical analysis software. This jitter analysis results are used to assess image quality, improve the structural design, and mitigate the disturbance impact.

We are developing a method to objectively quantify image quality and applying it to the optimization of fast magnetic resonance imaging methods. In MRI, to capture the details of a dynamic process, it is critical to have both high temporal and spatial resolution. However, there is typically a trade-off between the two, making the sequence engineer choose to optimize imaging speed or spatial resolution. In response to this problem, a number of different fast MRI techniques have been proposed. To evaluate different fast MRI techniques quantitatively, we use a perceptual difference model (PDM) that incorporates various components of the human visual system. The PDM was validated using subjective image quality ratings by naive observers and task-based measures as defined by radiologists. Using the PDM, we investigated the effects of various imaging parameters on image quality and quantified the degradation due to novel imaging techniques including keyhole, keyhole Dixon fat suppression, and spiral imaging. Results have provided significant information about imaging time versus quality tradeoffs aiding the MR sequence engineer. The PDM has been shown to be an objective tool for measuring image quality and can be used to determine the optimal methodology for various imaging applications.

To better meet the requirements of space wide-field optical cameras for the precision and freedom of the focusing mechanism, this paper designs a 2-dimensional adjustment mechanism based on a focusing mirror assembly (FMA) that can adjust defocus and tilt, according to the characteristics of and the long focal plane assembly (FPA) of the wide-field camera. To meet the requirements of space cameras for the surface accuracy and structural rigidity of mirror assemblies, this paper proposes a flexible connection structure and optimizes the geometric parameters of the flexible structure using design of experiments(DOE) methods. Through finite element simulation, the surface accuracy of the focusing mirror under different conditions was analyzed; the structural fundamental frequency after adding the adjustment mechanism was also analyzed. The control system for the adjustment mechanism was implemented using ZYNQ, and a kinematic test platform for the adjustment mechanism was constructed using a mechanical prototype of the FMA. The surface figure of the sub-aperture of the mirror was measured in an actual test environment. Under conditions of gravity, temperature rise, and maximum tilt, the root mean square (RMS) of the sub-aperture surface figure of the mirror is a maximum of 6.393nm, better than 1/80λ(λ = 0.632 μm). The fundamental frequency of the FMA and adjustment mechanism is 216Hz, the amplification factor of the response of the mirror assembly and the adjustment mechanism to sinusoidal and random vibration acceleration is less than 5 times. When adjusting the defocus, the translation positioning accuracy of the mechanism and the synchronization accuracy at ±1 field of view of the mirror are both 5 μm, better than 1/8 half focal depth. When adjusting the tilt, the angular positioning accuracy is 1.5''. In actual testing conditions, the RMS of the sub-aperture surface figure of the focusing mirror is a maximum of 4.889nm, which is better than 1/80λ. After defocus and tilt occur in the optical system, the adjustment mechanism can compensate and make the MTF of each field of view better than 0.5, and the service life of the adjustment mechanism is greater than 1500 times. The results show that the flexible connection structure of the adjustment mechanism can meet the requirements of the surface figure accuracy of the mirror surface when adjusting the tilt; the structural rigidity of the mirror assembly and the adjustment mechanism can meet the requirements of the space camera, and the translation adjustment range, angle adjustment range, translation positioning accuracy, synchronization accuracy, and angle positioning accuracy of the adjustment mechanism and its control system can meet the range and accuracy requirements of the space wide-field camera for the focusing mechanism. The adjustment mechanism can compensate for defocus and tilt caused by the optical system, and its lifespan meets the usage requirements of wide-field cameras.

PurposeTo assess the impact of prostate MRI image quality by means of the Prostate Imaging Quality (PI-QUAL) score, on the identification of extraprostatic extension of disease (EPE), predicted using the EPE Grade Score, Likert Scale Score (LSS) and a clinical nomogram (MSKCCn). MethodsWe retrospectively included 105 patients with multiparametric prostate MRI prior to prostatectomy. Two radiologists evaluated image quality using PI-QUAL (≥4 was considered high quality) in consensus. All cases were also scored using the EPE Grade, the LSS, and the MSKCCn (dichotomized). Inter-rater reproducibility for each score was also assessed. Accuracy was calculated for the entire population and by image quality, considering two thresholds for EPE Grade (≥2 and = 3) and LSS (≥3 and ≥ 4) and using McNemar’s test for comparison. ResultsOverall, 66 scans achieved high quality. The accuracy of EPE Grade ranged from 0.695 to 0.743, while LSS achieved values between 0.705 and 0.733. Overall sensitivity for the radiological scores (range = 0.235–0.529) was low irrespective of the PI-QUAL score, while specificity was higher (0.775–0.986). The MSKCCn achieved an AUC of 0.76, outperforming EPE Grade (=3 threshold) in studies with suboptimal image quality (0.821 vs 0.564, p = 0.016). EPE Grade (=3 threshold) accuracy was also better in high image quality studies (0.849 vs 0.564, p = 0.001). Reproducibility was good to excellent overall (95 % Confidence Interval range = 0.782–0.924). ConclusionAssessing image quality by means of PI-QUAL is helpful in the evaluation of EPE, as a scan of low quality makes its performance drop compared to clinical staging tools.

The American College of Radiology's (ACR) Nuclear Medicine and PET Accreditation Programs evaluate qualifications of personnel, equipment, image quality, and quality control measures. It is believed that these are primary factors that impact the quality of patient imaging. The ACR accreditation allows facilities to critique and improve their practices as part of their preparation for the accreditation evaluation process. The goals of the ACR Nuclear Medicine and PET Accreditation Programs are improvement in the quality of imaging, provision of educational information by raising awareness of imaging issues, and the recognition of imaging facilities which meet program objectives. This presentation will outline the program requirements, highlighting some of the common pitfalls that may cause deficiencies in both the clinical and phantom submissions.This presentation will provide participants with:1. General information describing the ACR Accreditation Programs2. Information about the Diagnostic Modality Accreditation Programs3. Specific information about the ACR Nuclear Medicine and PET Accreditation Program, to include the application process, clinical images submission and quality control requirements.

When a high-resolution satellite is imaging on orbit, the relative motion between the sensory optical elements inside the camera may be caused by micro-vibration, which results in degraded images. In order to study the effect of micro-vibration on high resolution satellite imaging, a micro-vibration analysis method of space camera based on target image is proposed in this paper. Firstly, the different factors of micro-vibration which will affect the image quality in different degrees are introduced. Then, the method which can realize the direct measurement of image motion in the image is proposed. The method can analyze the impact of micro-vibration on the space camera directly and get the accuracy number of the image motion, which can provide the basis for the influence analysis of the satellite image quality and the final correction. Finally, we take a factual space camera for example to calculate and analyze the test data by using this model on the condition of the satellite. We get the image motion set by the micro-vibration on focal plane and accomplish the influence analysis method of micro-vibration on high resolution satellite imaging. It is concluded that the proposed method is reasonable and practical. The method proposed by this paper can be referred to for improved design and vibration suppression.

Dose reduction techniques for computed tomography angiography (CTA) in children with cardiovascular diseases have the potential of reducing risks of radiation-induced cancer. To evaluate effectiveness of these techniques, both radiation dose and image quality must be compared. While clinically practical methods of estimating effective dose are available, there are no generally accepted metrics for the assessment of image quality in CTA. We introduce a measurable and reproducible image quality index, CTA QI. Using this index, along with calculated effective dose, we test the hypothesis that volume scan CTA delivers comparable image quality at substantially reduced radiation dose when compared to helical CTA. CTA QI is a measure of intraluminal contrast variation in three-dimensions, and it is calculated from standardized measurements of means and standard deviations of Hounsfield units in the thoracic descending aorta. From institutional database, 83 studies of CTA for thoracic cardiovascular diseases were retrospectively identified. CTA QI values were independently measured by two radiologists and compared using correlation. CTA QI and DLP-derived effective dose were compared for the following groups: non-cardiac gated wide-detector and helical CTA, ECG-synchronized retrospective wide-detector and helical CTA, ECG-synchronized wide detector retrospective and target technique CTA. Statistical significance was evaluated with the Student-t test. The correlations of CTA QI values between the radiologists were 0.83 and 0.92 for non-gated studies and ECG-synchronized studies respectively. Comparing non-gated volume scan CTA to helical CTA, there was a radiation dose reduction of 69% (P < 0.0001) without a significant change in CTA QI (1.4 ± 1.0 vs. 1.9 ± 1.4, P = 0.13). Comparing retrospective ECG-synchronized wide-detector CTA to helical CTA, there was a radiation dose reduction of 46% (P < 0.0001) with and improvement in CTA QI (1.0 ± 0.8 vs. 3.7 ± 3.4, P < 0.01). Comparing ECG-synchronized wide-detector target CTA to retrospective CTA, there was a radiation dose reduction of 68% (P < 0.0001, but at the cost of a significant reduction in CTA QI (2.0 ± 1.0 vs. 0.8 ± 0.4, P < 0.0044). CTA QI is a simple, reproducible metric of image quality suited for comparing CTA studies. Using this quality index, we establish that CTA performed with wide-detector scan techniques can yield substantially lower radiation dose without compromising diagnostic imaging quality. A wide-detector target technique can further reduce effective dose compared to wide-detector retrospective ECG-synchronization, but with a reduction in image quality.

PurposeTo evaluate and compare the image quality and diagnostic accuracy of Artificial Intelligence-assisted Compressed Sensing (ACS) sequences for lumbar disease, as an acceleration method for MRI combining parallel imaging, half-Fourier, compressed sensing and neural network and routine 2D sequences for lumbar spine.MethodsWe collected data from 82 healthy subjects and 213 patients who used 2D ACS accelerated sequences to examine the lumbar spine while 95 healthy subjects and 234 patients used routine 2D sequences. Acquisitions included axial T2WI, sagittal T2WI, T1WI, and T2-fs sequences. All obtained images of these subjects were analyzed in the light of calculating image quality factors such as signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) for selected regions of interest. The lumbar image quality, artifacts and visibility of lesion structure were assessed by two radiologists independently. Differences between the evaluation values above were tested for statistical significance by the Wilcoxon signed-ranks test. Inter-observer agreements of image quality between two radiologists were measured using Cohen’s kappa correlation coefficient.ResultsThe ACS accelerated sequences not only reduced the scanning time by 18.9%, but also retained basically the same image quality as the routine 2D sequences in both healthy subjects and patients. Artifacts are less produced on ACS accelerated sequences compared with routine 2D sequences (p < 0.05). Apart from this, there were no significant differences in quantitative SNR, CNR measurements and qualitative scores within reviewing radiologists for each group (p > 0.05). Moreover, inter-observer agreement between two radiologists in scoring image quality was substantial consistently for ACS accelerated sequences and routine sequences (kappa = 0.622–0.986).ConclusionCompared with routine 2D sequences, ACS accelerated sequences allow for faster lumbar spine imaging with similar imaging quality and present reliable diagnostic accuracy, which can potentially improve workflow and patient comfort in musculoskeletal examinations.

Forensic oral imaging quality of hand-held dental X-ray devices: Comparison of two image receptors and two devices

Part of the Future Circular Collider (FCC-hh) study is dedicated to the development of the 16 Tesla Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn superconducting dipole magnets. The design of the magnets was enabled by a cooperative effort of national research institutes, universities, and CERN. These actors tackled the problem from different sides, namely, the electromagnetic design, the mechanical design, the design of the quench protection systems, and the circuit design. The article deals with the design of the quench protection systems and provides solid motivations for the selection of the coupling-loss-induced quench (CLIQ) device as the baseline protection system for the FCC-hh main dipole magnets. The article shows that the design domains mentioned above are tightly interconnected and, therefore, the simulation of a quench event involves a complex multiphysics problem. The STEAM cosimulation framework, recently developed at CERN, is applied to address the complexity. The STEAM-SIGMA models are employed to simulate the CLIQ quench protection system applied to the FCC-hh dipole magnets. Dedicated CLIQ configurations are identified to protect the magnets in case of a quench. In addition, the possible implications of the CLIQ protection system on the mechanical design of the magnets are discussed. To this end, the article employs the co-simulation of different software platforms to calculate the mechanical stress during a quench. The results show that CLIQ does not produce additional stress.

Ferumoxytol is becoming more widely used as an off-label blood-pool contrast agent for MR angiography (MRA) and four-dimensional (4D) flow imaging in pediatric cardiovascular disease. Brand and generic versions of ferumoxytol are available with no information on relative efficacy as a contrast agent and safety profiles. This study evaluates patient safety and image quality of comparable dosages of generic ferumoxytol (GF) versus brand ferumoxytol (BF) with the following hypotheses: (1) Reducing the contrast dosage from 3 to 2mg/kg will not affect imaging quality and diagnostic accuracy of MRA and four-dimensional 4D flow. (2) GF and BF have similar image quality. (3) GF and BF have similar patient safety profiles. In an IRB-approved retrospective study, changes in vitals/clinical status between baseline, during infusion, and 30min post-infusion were analyzed in 3 groups: group 1 (3mg/kg BF, 216 patients, age: 19.29 ± 11.71years ranging from 2months to 62years), group 2 (2mg/kg BF, 47 patients, age: 15.35 ± 8.56years ranging from 10days to 41years), and group 3 (2mg/kg GF, 127 patients, age: 17.16 ± 12.18years ranging from 6days to 58years). Both pediatric and adult patients with congenital heart disease (CHD) indications were included within the study. Adverse reactions were classified as mild, moderate, or severe. Quantitative analysis of MR image quality was performed with signal-to-noise ratio (SNR) on MRA and velocity-to-noise ratio (VNR) on 4D flow. Qualitative grading of imaging features was performed by 2 experienced observers. Two-way analysis of variance (ANOVA) and chi-square tests were used for comparison with a P value of ≤ 0.05 used for significance. No statistical difference was found in clinical status and vital signs (P>0.05). No severe reactions were reported. 7.9% of GF patients experienced an adverse reaction compared to 2.3% with 3mg/kg BF and 8.4% with 2mg/kg BF. There was no statistical difference in SNR between the 3 groups (P>0.05). For 4D flow, 2mg/kg GF demonstrated an increase in VNR compared to 2mg/kg BF (P = 0.005). The qualitative scores for MRA and 4D flow were high (≥ 3) across all 3 groups. No significant difference was identified between 2mg/kg GF and BF in terms of safety profile and image quality. Given the small sample size of this study, further studies are required to confirm these results.

Funding Acknowledgements Type of funding sources: None. Purpose We sought to retrospectively evaluate the feasibility of identifying the fetal cardiac and thoracic vascular structures with non-gated dynamic balanced steady-state free precession MRI sequences. Methods We retrospectively assessed the visibility of cardiovascular anatomy in 66 fetuses without suspicion of congenital heart defect (mean gestational age 27+/- 4, range 21-38 weeks). Non-gated dynamic balanced steady-state free precession (SSFP) sequences were acquired in three planes (axial, coronal and sagittal) of the fetal thorax (slice thickness 4-5mm, FOV 400, FA 60°, matrix 256x256). The images were analysed following a segmental approach in consensus reading by an experienced paediatric cardiologist and radiologist. An imaging score was defined by giving one point to each visualized structure. Basic diagnostic structures included the atria, ventricles, systemic veins, right and left ventricular outflow tracts (RVOT/LVOT), aortic arch, descending aorta (DAO), ductus arteriosus and thymus (12 points); advanced diagnostic features included the atrioventricular (AV) valves, pulmonary arteries and veins, supraaortic arteries and trachea, yielding a maximum score of 21 points. Image quality was rated from 0 (poor) to 2 (good). The influence of gestational age (GA), field strength, placenta position, and maternal panniculus on image quality and imaging score were tested. Results 34 scans were performed at 1.5 T, 32 at 3 T. Heart position, atria and ventricles could be seen in all 66 fetuses. Basic diagnosis (&amp;gt;12 points) was achieved in 60 (90%) cases, with visualization of the IVC and SVC in 65 (98%) and 63 (95%), RVOT in 62 (94%), LVOT in 61 (92%), aortic arch in 60 (91%), DAO in 64 (97%), ductus arteriosus in 59 (89%) and thymus in 50 (76%) fetuses. The AV valves were recognised in 55 (83%), the pulmonary arteries in 35 (53%), at least one pulmonary vein in 46 (70%), the supraaortic arteries in 42 (64%), and the trachea in 59 (89%) fetuses. The mean imaging score was 16.8 +/- 3.7. Maternal panniculus (r -0.3; p 0.01) and gestational age (r 0.6; p &amp;lt; 0.001) correlated with imaging score. Field strength influenced image quality, with 1.5 T being better than 3T images (p 0.04), but not the total imaging score. Imaging score or quality were independent from placenta position. Conclusions Fetal heart MRI with a non-gated SSFP sequence in multiple planes enables recognition of basic cardiovascular anatomy. Advanced diagnostics may be limited by thick maternal panniculus, lower GA and higher field strength.

The design of reliable protection systems is essential in order to guarantee the secure operation of power systems. The coordination of the response of protective equipment under fault conditions is a fundamental problem which is usually formulated as a non-linear optimization problem with the objective of minimizing the total operating time of the protection system. In general, optimal protection coordination can be regarded as a well-studied problem, with the existing literature featuring the application of a wide range of solution techniques. However, recent advances in the area of artificial intelligence and the increasing availability of near real-time measurements from distribution systems offer the possibility to envision adaptive protection systems capable of operating optimally under different power system operating conditions and, potentially, of being more resilient, by assigning local decision-making autonomy to relays, instead of relying on a centralized system to coordinate protective devices. To this end, in this study optimal protection coordination is cast as a reinforcement learning problem and relays are viewed as autonomous agents that can manipulate their time dial settings in order to optimally respond to signals from their environment, i.e., the power system. The reinforcement learning problem is solved by applying the Q-learning algorithm. The results of the case study indicate that this framework is capable of providing settings that achieve both a fast and coordinated protection system.