Selective Shield Research Articles

Stealth RF energy harvesting in MRI using selective shielding.

To utilize the transmit radiofrequency (RF) field in MRI as a power source, near or within the field of view but without affecting image quality or safety. Power harvesting is performed by RF induction in a resonant coil. Resulting RF field distortion in the subject is canceled by a selective shield that couples to the harvester while being transparent to the RF transmitter. Such shielding is designed with the help of electromagnetic simulation. A shielded harvester of 3 cm diameter is implemented, assessed on the bench, and tested in a 3T MRI system, recording power yield during typical scans. The concept of selective shielding is confirmed by simulation. Bench tests show effective power harvesting in the presence of the shield. In the MRI system, it is confirmed that selective shielding virtually eliminates RF perturbation. In scans with the harvester immediately adjacent to a phantom, up to 100 mW of average power are harvested without affecting image quality. Selective shielding enables stealthy RF harvesting which can be used to supply wireless power to on-body devices during MRI.

Research progress on the regulation and mechanism of borneol on the blood-brain barrier in pathological states: a narrative review focused on ischemic stroke and cerebral glioma.

The blood-brain barrier (BBB) serves as a dynamic, selective shield, safeguarding the central nervous system (CNS) by separating the brain from circulating blood, preserving its microenvironment, and ensuring stability. However, in the presence of brain pathology, drug delivery across the BBB and blood-tumor barrier (BTB) becomes challenging, hindering effective treatments. Borneol exhibits promise in bidirectionally modulating the BBB under pathological conditions, suggesting at potential clinical applications for related diseases. Our primary goal in this review is to investigate borneol's potential clinical utility in bidirectionally regulating the BBB under pathological conditions. The PubMed database, CNKI (China National Knowledge Infrastructure), Wanfang Data were searched to retrieve articles on animal experiments and cell-based research published from January 1, 2003, to May 1, 2023, using the following medical subject headings (MeSH) terms: borneol, blood-brain barrier, ischemic stroke, cerebral gliomas, anti-inflammatory. The search was limited to articles published in English and Chinese. In total, 86 articles were deemed eligible for inclusion in this study. The breakdown of the BBB is a key pathological process in ischemic stroke and cerebral glioma. When used alone, the lipophilic properties of borneol can reduce the permeability of the BBB and restore its normal function, thereby repairing brain damage and protecting brain tissue. Its specific protective effects may be related to inflammatory regulation mechanisms. The anti-inflammatory and protective effects of borneol can be used to improve and treat lesions caused by ischemic stroke and cerebral glioma. Furthermore, when combined with other drugs, borneol can accelerate the opening of the BBB, improve permeability through physiological processes, and enhance drug penetration and distribution in the brain without causing pathological damage to the brain. This review summarizes the mechanisms by which borneol regulates the BBB and BTB in ischemic stroke and cerebral glioma, and discusses the potential clinical applications of borneol in the treatment of these diseases. It is believed that in the future, as research methods are refined, more effective and targeted therapies for cerebral glioma and ischemic stroke will be explored related to the protective mechanism of the BBB under pathological conditions with borneol alone or in combination with other drugs.

Pulmonary CT scans of white rabbits using the selective photon shield technique of the third-generation dual-source CT

This study aims to optimise the protocol for the low-dose pulmonary computed tomography (CT) scanning of infants by studying the effects of the selective photon shield (SPS) technique of the third-generation dual-source CT (DSCT) on the image quality and radiation dose of a chest CT in white rabbits under different tube currents. Twelve white rabbits of a similar weight to an infant were selected and randomly divided into an experimental group and a control group. The experimental groups (A1–A5) were scanned at low dose by the third-generation DSCT using SPS under different tube current × time (60, 50, 40, 30, and 20 mAs). The control group (B) was scanned under a conventional tube voltage (100 kV) and current × time (20 mAs). Advanced model iterative reconstruction at strength three was used for the objective and subjective evaluation of the image quality and radiation dose of the lung and mediastinal windows. With the standard deviation of the air in the trachea as image noise, the signal-to-noise ratio (SNR), contrast-to-noise ratio, and CT values of each site were evaluated. Radiation doses were compared using the volume CT dose index, dose length product, and effective dose. The differences in subjective image quality between groups A2 and B were not statistically significant (P = 0.34). The differences in the SNRs of the lung and mediastinal windows between groups A2 and B were not statistically significant (P > 0.05). The radiation dose of group A2 was 83.2% lower than that of group B. The SPS of the third-generation DSCT under 50 mAs might be applied in the pulmonary CT examination of infants.

A novel spectrally selective radiation shield for cooling a photovoltaic module

The cooling of photovoltaic panels plays an important role in improving electrical efficiency and increasing the lifetime. In this paper, a radiation shield for filtering the thermal part of solar irradiance has been proposed as a passive cooling method. A 3D model of a PV module with all consisting layers has been numerically simulated. The radiative transfer equation has been solved by discrete ordinates (DO) method. The numerical results of the uncooled PV module have been compared with the experimental data. The radiation shields with 40% and 80% reflections in the wavelength interval between 1 μm and 2.4 μm have been performed to reduce the thermal effect of solar irradiation over the PV module. The effects of radiation shield on the instantaneous and monthly average surface temperature of the PV module have been investigated. It has been found that the effect of radiation shield on temperature reduction of the PV module is more considerable in seasons with high solar irradiation. The numerical results show that the radiation shield with 80% reflectivity has more effect on temperature reduction and the electrical efficiency of the PV module. The numerical results reveal that, for solar irradiation between 1025 and 1142 W/m2, the radiation shield with 80% reflection can increase the electrical efficiency by about 5.14%–5.72%.

Mechanically Robust and Spectrally Selective Convection Shield for Daytime Subambient Radiative Cooling.

As a passive cooling strategy, radiative cooling is becoming an appealing approach to dissipate heat from terrestrial emitters to the outer space. However, the currently achieved cooling performance is still underperforming due to considerable solar radiation absorbed by the emitter and nonradiative heat transferred from the surroundings. Here, we proposed a mechanically robust and spectrally selective convection shield composed of nanoporous composite fabric (NCF) to achieve daytime subambient radiative cooling. By selectively reflecting ∼95% solar radiation, transmitting ∼84% thermal radiation, and suppressing the nonradiative heat transferred from warmer surroundings, the NCF-based radiative cooler demonstrated an average daytime temperature reduction of ∼4.9 °C below the ambient temperature, resulting in an average net radiative cooling power of ∼48 W/m2 over a 24 h measurement. In addition, we also modeled the potential cooling capacity of the NCF-based radiative cooler and demonstrated that it can cover the cooling demands of energy-efficient residential buildings in most regions of China. Excellent spectral selectivity, mechanical strength, and weatherability of the NCF cover enable a much broader selection for the emitters, which is promising in the real-world deployment of direct daytime subambient radiative cooling.

The Selective Shield of Due Process: Analysis of the U.S. Department of Education's 2020 Title IX Regulations on Live Cross‐Examination

AbstractThe U.S. Department of Education (DoE) released new Title IX regulations in May 2020, including the requirement that postsecondary institutions conduct live hearings with direct cross‐examination for sexual misconduct reports. The 2,033‐page document included a summary of public comments and the DoE's discussion of those comments. We analyzed this publicly available document to answer two questions. (1) What are the primary concerns of the cross‐examination requirement for victims within the Department's summary of public comments? (2) How did the Department respond to these victim concerns? We conducted a content analysis, with a specific focus on the DoE's summary of survivor‐focused comments regarding cross‐examination and the DoE's discussion of and changes made in response to those comments. We identified four overarching survivor‐focused concerns and four categories of DoE responses. Our findings suggest that the DoE did not meaningfully address survivor‐focused concerns, but instead, selectively wielded “due process” as a shield to deflect critiques and legitimize the myth that sexual misconduct allegations inherently lack “credibility.” The lack of protections for victims is a significant departure from legal norms in other settings. Our findings identify the importance of legislators working with survivor‐activists, practitioners, and researchers to ensure complainants receive adequate procedural protections.

Not All Green Is Tophi: The Importance of Optimizing Minimum Attenuation and Using a Tin Filter to Minimize Clumpy Artifacts on Foot and Ankle Dual-Energy CT.

OBJECTIVE. The clumpy artifact has a high misdiagnosis rate, but the artifact has not been well studied. The aims of this study were to evaluate the frequency and location of clumpy artifacts, the rate of misdiagnosis of clumpy artifacts as gout, and the effects of raising the minimum attenuation value and using a selective photon shield in dual-energy CT (DECT). MATERIALS AND METHODS. Forty patients without gout who underwent foot and ankle DECT were enrolled in this study. Images in both sets were randomly assigned a minimum attenuation of 130 HU or 150 HU. Three radiologists independently checked all images for presence, volume, and location of green color-coded pixelation and graded their findings according to a 4-point confidence scale, frequency, and volume. Misdiagnosis rate and misdiagnosis score were compared using the Wilcoxon signed rank and McNemar tests. RESULTS. In set 1, the frequency of clumpy artifacts in DECT with the minimum attenuation set to 130 HU and 150 HU were 81% and 68%, respectively. For all three readers, the misdiagnosis rate and misdiagnosis score decreased when changing the minimum attenuation from 130 HU to 150 HU. In set 2, with the minimum attenuation set to 130 HU, the frequency of the clumpy artifact was 44%; with the minimum attenuation set to 150 HU, no clumpy artifacts were seen. CONCLUSION. Clumpy artifacts occurred frequently in DECT without a tin filter. Setting the minimum attenuation to the higher value of 150 HU reduced the frequency of clumpy artifacts, and adding a tin filter to DECT greatly reduced their occurrence.

Application Value of Selective Photon Shield in Dual-Energy Computed Tomography Angiography for Diagnosis of Intracranial Aneurysms.

The aim of the study was to investigate the image quality of dual-energy computed tomography angiography (DECTA) using the selective photon shield (SPS) technique to diagnose intracranial aneurysms. Eighty patients with a suspected intracranial aneurysm were randomly assigned to undergo DECTA with SPS (ie, SPS-DECTA) or DECTA without SPS (ie, DECTA). The objective image quality of these 2 groups was compared with digital subtraction angiography and surgical results as the reference. The location, number, and morphology of the aneurysms were evaluated between the 2 groups. The display degree and the size of aneurysmal neck and the diameters (ie, long and short axis) of the aneurysm were compared between the 2 groups. The signal-to-noise ratio and contrast-to-noise ratio of SPS-DECTA were significantly higher than those of DECTA (P < 0.05). The difference between the 2 groups in intracranial vascular subjective scoring was not statistically significant (P > 0.05). In 30 of the 40 patients in the SPS-DECTA group, an aneurysm was detected without misdiagnosis or missed diagnosis. The aneurysm location, aneurysm number, and measurements by the 2 methods were closely correlated without significant statistical differences (the R values were 0.953, 0.982, and 0.974, respectively; P = 0.000). The detection rate was 93% (26/28 patients). In the DECTA group, 2 patients were misdiagnosed. Mean long and short diameter and neck size by three-dimensional digital subtraction angiography were 5.82 ± 3.27, 4.67 ± 3.31, and 3.29 ± 1.38 mm, respectively. Aneurysm locations, number, and neck size by the 2 methods were closely correlated without a significant statistical difference (R values were 0.964, 0.968, and 0.856, respectively; P = 0.000). The SPS-DECTA is very accurate for diagnosing intracranial aneurysms and could be a routine noninvasive screening method.

Influence of selective photon shield combined with sinogram-affirmed iterative reconstruction on image quality and radiation dose during dual-energy CT angiography-mediated diagnosis of intracranial aneurysms

Objective: To investigate the influence of a selective photon shield (SPS) combined with sinogram-affirmed iterative reconstruction (SAFIRE) on image quality and radiation dose during application of dual-energy CT angiography (CTA) for diagnosis of intracranial aneurysms. Methods: We retrospectively reviewed clinical data for 80 patients with diagnoses of spontaneous subarachnoid hemorrhage. All patients underwent three-dimensional digital subtraction angiography scans within 1 week after CTA. Data for patients in the conventional method group were subjected to filtered-back-projection reconstruction, while data for patients in the experimental method group were subjected to SAFIRE reconstruction. Image quality and scanning radiation dose were evaluated. Results: Background noise was significantly lower in the experimental method group than in the conventional method group, while the mean CT value did not differ between the groups. Signal-to-noise ratios were significantly higher in the experimental method group than in the conventional method group. However, the average CT value, contrast-to-noise ratio, and image quality scores did not differ between groups. All scores indicated acceptability for clinical diagnosis. The dose index of volume and effective dose were significantly lower in the experimental method group than in the conventional method group. Surgical verification showed that the detection rates in the experimental and conventional method groups were 100% (29/29) and 96% (25/26), respectively. Conclusions: SPS combined with SAFIRE applied for analysis of dual-energy CTA data improved the quality of CT images, reduced the radiation dosage, and increased diagnostic accuracy. Advances in knowledge: SPS combined with SAFIRE may improve the accuracy of diagnosis of intracranial aneurysms.

Design of Frequency Selective Band Stop Shield Using Analytical Method

In this article, a high-order frequency selective band-stop EMC (electromagnetic compatibility) shield is designed using multilayer square loop while each loop resonates at the specific desired frequency. The glass material is picked out as the preferred substrate for the designing process. In contrast to the computationally intensive numerical approaches (software), the equivalent circuit model offers a simple alternative method in FSS (frequency selective surface) analyses which is useful for quickly predicting the performance of FSS. The proposed FSS can be synthesized based on microwave filter theory and the synthesized FSS can control transmission-zero frequencies. A three zero-transmission transparent window is designed using the proposed method, in which 30dB insertion loss is achieved for 6 to 10 GHz bandwidth and optical opacity of the structure is 85%. The response of the analytical model is compared with the results of full-wave simulation. As a result, it predicts quite well the resonant frequencies of the designed FSS.

Influence of selective photon shield combined with sinogram affirmed iterative reconstruction on image quality and radiation dose of dual-energy CT angiography for the diagnosis of intracranial aneurysms

Objective To investigate the influence of selective photon shield combined with sinogram affirmed iterative reconstruction(SAFIRE) on image quality and radiation dose of dual-energy CTA for the diagnosis of intracranial aneurysms. Methods The study retrospectively analyzed 80 patients with spontaneous subarachnoid hemorrhage, who were diangosed having intracranial aneurysms by three-dimensional DSA and surgery and underwent cerebral CTA examination. According to CTA scanning method, the patients were divided into conventional group and experimental group (n=40 for each). All patients underwent head CTA in dual energy mode with selective photon shield (SPS) technology. The scanning protocols of conventional group were tube voltages 80 kV and sn 140 kV, tube currents 300 mAs and 150 mAs, filtered back projection (FBP) reconstruction. The scanning protocols of experimental group were tube voltages 80 kV, sn 140 kV, tube currents 200 mAs, 100 mAs, SAFIRE reconstruction. Objective image quality evaluation indexes included the average CT value of all parts (occipital lobe, the anterior cerebral artery, middle cerebral artery and posterior cerebral artery), the background noise, the signal-to-noise ratio (SNR) and contrast to noise ratio (CNR), and subjective image quality was also assessed. Radiation dose was recorded. With 3D DSA or operation findings as gold standard, coincidence rate of intracranial aneurysm detection was calculated both in experimental group and conventional group. Objective image quality evaluation index and radiation dose both in conventional group and experimental group were compared with two independent two-sample t test, subjective image scores with non parameter test of independent samples. Results The noise of occipital lobe, the anterior cerebral artery, middle cerebral artery and posterior cerebral artery were (5.34±1.22), (39.94±15.96), (39.94±15.96) and (23.17± 5.51) HU in conventional group, (4.44 ± 1.08), (24.91 ± 9.36), (35.03 ± 13.65) and (20.61 ± 5.08) in experimental group (the value of t test were 2.508,3.742,2.788 and 2.563, P 0.05). Image quality scores of the conventional group and experimental group were (4.86± 0.07) and (4.67±0.21) without statistical difference (Z=- 0.443,P=0.621). CTDIvol and ED were (20.61 ± 1.07) mGy and (0.79 ± 0.04) mSv in conventional group and (13.59 ± 1.27) mGy and (0.54 ± 0.06) mSv in experimental group (the value of t test were 24.039 and 15.813, P<0.01). With 3D DSA or operation findings as gold standard, intracranial aneurysm diagnosis coincidence of experimental group was 100.0% (29/29), while coincidence rate of conventional group was 96.0% (25/26). Conclusion SPS combined with SAFIRE techniques applied in dual energy CTA for the diagnosis of intracranial aneurysms could improve the quality of CT image and reduce the radiation dosage and have a high diagnosis accuracy. Key words: Intracranial aneurysm; Tomography, X-ray computed; Radiation dosage; Image quality

TU‐E‐210A‐02: Dual Energy Imaging with Dual Source Systems

TU‐E‐210A‐02: Dual Energy Imaging with Dual Source Systems