Evaluation of a two-dimensional Moire-free antiscatter grid for cone-beam computed tomography.

BACKGROUND: Scatter radiation is a traditional problem in cone-beam computed tomography (CBCT). Accordingly, numerous methods have been researched for scatter reduction in terms of software- or hardware-based solutions. The concept of a two-dimensional antiscatter grid (2D-ASG) has been shown to provide a solution to the scatter reduction in CBCT. However, the use of an ASG makes it challenging to use in clinical CBCT systems because it causes Moire artifacts of the image. PURPOSE: We have developed a Moire-free 2D-ASG that was designed to solve the Moire artifact and the scatter radiation problems. We provide the experimental results pertaining to the image quality measurements from the evaluation of the 2D-ASG compared with those obtained from a one-dimensional antiscatter grid (1D-ASG) and no antiscatter grid (No-ASG) to demonstrate the quantitative extent of the improvements. METHODS: The 2D-ASG, fabricated based on a sawing process with a graphite body, was prepared to evaluate image quality improvements. Projection images for Pro-CT MK II phantom were acquired using the CBCT testbed of sample rotation type and reconstructed by Feldkamp-Davis-Kress (FDK) algorithm without any filters. We measured the contrast-to-noise ratio (CNR) and uniformity index for the cupping artifacts of the 2D-ASG, 1D-ASG, and No-ASG cases. RESULTS: 2D-ASG considerably reduced the cupping artifacts owing to the scatter reduction compared with the 1D-ASG and No-ASG cases. The cupping artifacts were reduced by 85% in the 2D-ASG compared with No-ASG, while the cupping artifacts were reduced by 63% in 1D-ASG compared with No-ASG. The 2D-ASG also yielded a CNR improvement. The average CNR improvements for eight insert materials were 47% in the 2D-ASG compared with No-ASG, while the CNR was improved by 36% in the 1D-ASG compared with No-ASG. CONCLUSIONS: We demonstrated that the Moire-free 2D-ASG improved the image quality by removing scatter radiation in CBCT compared with 1D-ASG and No-ASG. We believe that the Moire-free 2D-ASG can become one of the effective ways to solve the scatter radiation problem in CBCT images because it provides usability and has the potential to have synergistic effects on other methods, such as bow-tie filter and scatter correction.

Field study of the indoor environments for preventing the spread of the SARS-CoV-2 in Seoul.

Despite the prolonged global spread of COVID-19, few studies have investigated the environmental influence on the spread of SARS-CoV-2 RNA with a metropolitan scale, particularly the detection of SARS-CoV-2 after disinfection at multi-use facilities. Between February 2020 and January 2021, 1,769 indoor air samples and object surfaces were tested at 231 multi-use facilities where confirmed cases were known to have occurred in Seoul, to determine whether SARS-CoV-2 RNA could be detected even after disinfection. Samples were collected by air scanner and swab pipette and detected by real-time RT-PCR. As a result, 10 (0.56%) positive samples were detected despite disinfection. The common environmental features of all 10 were surfaces that contained moisture and windowless buildings. With the aim of preventing the spread of COVID-19, from January to February 2021, we next conducted 643 preemptive tests before the outbreak of infections at 22 multi-use facilities where cluster infections were frequent. From these preemptive inspections, we obtained five (0.78%) positive results from two facilities, which enabled us to disinfect the buildings and give all the users a COVID-19 test. Based on the study purpose of finding and investigating cases of positive detection even after disinfection in the field through long-term environmental detection in a large city, our preemptive investigation results helped to prevent the spread of infectious diseases by confirming the potential existence of an asymptomatic patient.

Degradation of chemical warfare agents over cotton fabric functionalized with UiO-66-NH2.

Herein, cotton fabric was treated with an alkaline solution to increase the content of surface hydroxyl groups and then functionalized with UiO-66-NH2, a nanoporous metal-organic framework. Instrumental analysis of the thus treated fabric revealed that its surface was covered with UiO-66-NH2 crystals in a uniform manner. The ability of the functionalized fabric to degrade two chemical warfare agents (soman and sulfur mustard) was probed by testing its permeability to these two agents (swatch testing), and the excellent degradation performance was concluded to be well suited for a broad range of filtration and decontamination applications.

Regulation of magnesium-inhibited cation current by actin cytoskeleton rearrangement.

Magnesium-inhibited, non-selective cation current (I(MIC)) is activated by depletion of intracellular Mg(2+) and ATP. I(MIC) transports various divalent cations including Mg(2+) and Ca(2+), and is involved in cell viability. We investigated the effect of actin dynamics on I(MIC). Formation of a stable cortical actin network by calyculin A inhibited the activation of I(MIC), while the actin depolymerizing reagent, cytochalasin D, reversed the inhibition. Induction of a dense cortical actin layer by transfecting the constitutively active form of RhoA also inhibited the activation of I(MIC). These results suggest that the activation of I(MIC) may be dynamically regulated by actin cytoskeleton rearrangement.

Modulation of delayed rectifier potassium channels by alpha1-adrenergic activation via protein kinase C zeta and p62 in PC12 cells.

When PC12 cells are exposed to nerve growth factor (NGF), they extend neurites and express autonomic ganglion cell properties. We have previously shown that NGF is capable of inducing p62 expression, enabling the formation of the protein kinase C zeta (PKCzeta)-p62-Kvbeta (beta-subunit of delayed rectifier K+ channel) complex, a Kv channel-modulating complex. The formation of this complex results in the shifting of the Kv channel activation curve to the left via PKCzeta activity. During the experiments, we noted that PC12 cells in a high-density culture exhibited a Kv channel activation curve shift similar to that observed in the NGF-treated cells. Therefore, we hypothesized that catecholamines released from PC12 cells may induce p62 expression. In order to test this idea, cells in a low-density culture were treated for 24h with norepinephrine (NE). In these cells, we noted a leftward shift of the activation curve. The presence of the alpha1-adrenergic antagonist specifically prevented the effects of NE. Pre-treatment of the low-density cells with alpha1-agonists induced changes similar to those associated with NE, confirming that NE modulates Kv channels via the alpha1-adrenergic receptor. NE's effects were blocked by treatment with PKCzeta specific inhibitors. Using Western blotting, we observed increased levels of p62 expression in both the high-density cells and the NE-treated low-density cells. These results suggest that locally secreted NE induces an increase in p62 expression, and also exerts a modulatory effect on Kv channels via the PKCzeta-p62-Kvbeta channel modulating complex.