ABSTRACT
Objective:To explore whether the specific synaptic vesicle glycoprotein 2A (SV2A) targeted imaging agent ( R)-4-(3-fluoro-5-(fluoro- 18F)phenyl)-1-((3-methylpyridin-4-yl)methyl)pyrrolidin-2-one ( 18F-SDM-8) can be used to detect epileptic foci. Methods:Twenty male Sprague-Dawley (SD) rats (8-9 weeks) were injected with 1.2 μl of kainic acid (16 rats in the epilepsy group) or saline (4 rats in the control group) into the right hippocampus. 18F-SDM-8 and 18F-FDG mircoPET/CT imaging were respectively performed at 1-2 d (acute phase), 6-7 d (incubation period) and 45-60 d (chronic phase) after the seizure. Asymmetric index (AI) was used to evaluate the epileptic foci identify ability of 18F-SDM-8. Paired t test, Mann-Whitney U test and Pearson correlation analysis were used to analyze data. Results:In the three periods of 18F-SDM-8 imaging, the differences of AI of hippocampus between the epilepsy group and control group were statistically significant ( z values: from -2.64 to 2.67, all P<0.05). Both imaging agents had asymmetric uptake in the epilepsy group (right was lower than left), and the decrease in the medial right temporal lobe was the most significant. The pathological staining results were consistent with the imaging results. In the chronic phase of the epilepsy group, the differences of 18F-SDM-8 SUV mean (right versus left) in each brain area of interest were statistically significant ( t value: from -33.40 to -5.60, all P<0.05). The asymmetric uptake of the two imaging agents in the hippocampus had a better correlation ( r=0.97, P=0.001), and the AI of 18F-SDM-8 ((34.2±8.4)%) in this area was 1.4 times higher than that of 18F-FDG ((24.6±4.7)%). Conclusions:18F-SDM-8 PET is a promising method to test the level of SV2A. It can reflect the changes of SV2A in the rat epilepsy model induced by intrahippocampal injection of kainic acid, and improve the sensitivity of molecular imaging for epileptic foci.
ABSTRACT
The stress monitoring of bolted connections is crucial in the evaluation of mechanical systems' structural health, and the ultrasonic method using TOF (Time of Flight) is considered promising in this application. However, the discrete nature of couplant layer characteristics can deteriorate the robustness of the ultrasonic method significantly. Here, for the purpose of deducting the coupling error, a compensating method of TOF is proposed. In this method, the components of the waves backscattering from bolt bearing surface within the temporal signal are filtered and utilized. The analytical coupling error correction model is established and the influences of the installation eccentricity upon the model are analyzed. Meanwhile, the proposed method is further verified by a finite element simulation and the results are consistent with the analytical derivations. Ultimately, the proposed method is experimentally validated and the scattering components are extracted from the pulse echo signal by using the synchrosqueezed wavelet transform. The results imply that, after being compensated by the proposed method, the stress measurement error decreased from 5% to 1%. This research provides a novel perspective in reducing the coupling error in a concise manner and is potential in improving the practicality of the ultrasonic bolt axial stress measurement methods.
ABSTRACT
Laser-induced breakdown spectroscopy has become a very attractive technique in the field of chemical analysis.The technique utilizes a laser focused on a small spot to create a micro-plasma on the sample surface.In recent years, laser-induced breakdown spectroscopy (LIBS) is a frontier analysis technique in spectrometric analysis, with the advantages such as real-time, online and non-contact analysis.The research and development of various instruments based on this technology has attracted great attention of researchers.In the article, we reviewed the research progress of LIBS instrument from the components and field equipment in recent years, mainly including portable LIBS, handheld LIBS and remote LIBS.
