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Leaman, Felix,Herz, Aljoscha,Brinnel, Victoria,Baltes, Ralph,Clausen, Elisabeth Techno-Press 2020 Structural monitoring and maintenance Vol.7 No.1
One of the most important aspects in structural health monitoring is the detection of fatigue damage. Structural components such as heavy-duty bolts work under high dynamic loads, and thus are prone to accumulate fatigue damage and cracks may originate. Those heavy-duty bolts are used, for example, in wind power generation and mining equipment. Therefore, the investigation of new and more effective monitoring technologies attracts a great interest. In this study the acoustic emission (AE) technology was employed to detect incipient damage during fatigue testing of a M36 bolt. Initial results showed that the AE signals have a high level of background noise due to how the load is applied by the fatigue testing machine. Thus, an advanced signal processing method in the time-frequency domain, the Hilbert-Huang Spectrum (HHS), was applied to reveal AE components buried in background noise in form of high-frequency peaks that can be associated with damage progression. Accordingly, the main contribution of the present study is providing insights regarding the detection of incipient damage during fatigue testing using AE signals and providing recommendations for further research.
Kim, Dong-Yeon,Kim, Hyeon Sik,Reder, Sybille,Zheng, Jin Hai,Herz, Michael,Higuchi, Takahiro,Pyo, AYoung,Bom, Hee-Seung,Schwaiger, Markus,Min, Jung-Joon Society of Nuclear Medicine 2015 The Journal of nuclear medicine Vol.56 No.10
<P>Despite substantial advances in the diagnosis of cardiovascular disease, there is a need for <SUP>18</SUP>F-labeled myocardial perfusion agents for the diagnosis of ischemic heart disease because current PET tracers for myocardial perfusion imaging have a short half-life that limits their widespread clinical use in PET. Thus, <SUP>18</SUP>F-labeled fluoroalkylphosphonium derivatives (<SUP>18</SUP>F-FATPs), including (5-<SUP>18</SUP>F-fluoropentyl)triphenylphosphonium cation (<SUP>18</SUP>F-FPTP), (6-<SUP>18</SUP>F-fluorohexyl)triphenylphosphonium cation (<SUP>18</SUP>F-FHTP), and (2-(2-<SUP>18</SUP>F-fluoroethoxy)ethyl)triphenylphosphonium cation (<SUP>18</SUP>F-FETP), were synthesized. The myocardial extraction and image quality of the <SUP>18</SUP>F-FATPs were compared with those of <SUP>13</SUP>N-NH<SUB>3</SUB> in rat models. <B>Methods:</B> The first-pass extraction fraction (EF) values of the <SUP>18</SUP>F-FATPs (<SUP>18</SUP>F-FPTP, <SUP>18</SUP>F-FHTP, <SUP>18</SUP>F-FETP) and <SUP>13</SUP>N-NH<SUB>3</SUB> were measured in isolated rat hearts perfused with the Langendorff method (flow velocities, 0.5, 4.0, 8.0, and 16.0 mL/min). Normal and myocardial infarction rats were imaged with small-animal PET after intravenous injection of 37 MBq of <SUP>18</SUP>F-FATPs and <SUP>13</SUP>N-NH<SUB>3.</SUB> To determine pharmacokinetics, a region of interest was drawn around the heart, and time–activity curves of the <SUP>18</SUP>F-FATPs and <SUP>13</SUP>N-NH<SUB>3</SUB> were generated to obtain the counts per pixel per second. Defect size was analyzed on the basis of polar map images of <SUP>18</SUP>F-FATPs and <SUP>13</SUP>N-NH<SUB>3.</SUB> <B>Results:</B> The EF values of <SUP>18</SUP>F-FATPs and <SUP>13</SUP>N-NH<SUB>3</SUB> were comparable at low flow velocity (0.5 mL/min), whereas at higher flows EF values of <SUP>18</SUP>F-FATPs were significantly higher than those of <SUP>13</SUP>N-NH<SUB>3</SUB> (4.0, 8.0, and 16.0 mL/min, <I>P</I> < 0.05). Myocardium-to-liver ratios of <SUP>18</SUP>F-FPTP, <SUP>18</SUP>F-FHTP, <SUP>18</SUP>F-FETP, and <SUP>13</SUP>N-NH<SUB>3</SUB> were 2.10 ± 0.30, 4.36 ± 0.20, 3.88 ± 1.03, and 0.70 ± 0.09, respectively, 10 min after injection, whereas myocardium-to-lung ratios were 5.00 ± 0.25, 4.33 ± 0.20, 7.98 ± 1.23, and 2.26 ± 0.14, respectively. Although <SUP>18</SUP>F-FATPs and <SUP>13</SUP>N-NH<SUB>3</SUB> sharply delineated myocardial perfusion defects, defect size on the <SUP>13</SUP>N-NH<SUB>3</SUB> images was significantly smaller than on the <SUP>18</SUP>F-FATP images soon after tracer injection (0–10 min, <I>P</I> = 0.027). <B>Conclusion:</B> <SUP>18</SUP>F-FATPs exhibit higher EF values and more rapid clearance from the liver and lung than <SUP>13</SUP>N-NH<SUB>3</SUB> in normal rats, which led to excellent image quality in a rat model of coronary occlusion. Therefore, <SUP>18</SUP>F-FATPs are promising new PET radiopharmaceuticals for myocardial perfusion imaging.</P>