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RISS 인기검색어
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- 저자 : Heemann (검색결과 3 건)
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Katharina Hollerieth,Bernhard Gaßmann,Stefan Wagenpfeil,Stephan Kemmner,Uwe Heemann,Konrad Friedrich Stock 대한초음파의학회 2018 ULTRASONOGRAPHY Vol.37 No.2
Purpose: This study was conducted to determine the influence of standoff material on acoustic radiation force impulse (ARFI) measurements in an elasticity phantom by using two different probes. Methods: Using ARFI elastography, 10 observers measured the shear wave velocity (SWV, m/sec) in different lesions of an elasticity phantom with a convex 4C1 probe and a linear 9L4 probe. The experimental setup was expanded by the use of an interposed piece of porcine muscle as standoff material. The probe pressure on the phantom was registered. Results: Faulty ARFI measurements occurred more often when quantifying the hardest lesion (74.0 kPa 4.97 m/sec) by the 9L4 probe with the porcine muscle as a standoff material interposed between the probe and the phantom. The success rate for ARFI measurements in these series was 52.4%, compared with 99.5% in the other series. The SWV values measured with the 9L4 probe were significantly higher (3.33±1.39 m/sec vs. 2.60±0.74 m/sec, P<0.001 in the group without muscle) and were closer to the reference value than those measured with the 4C1 probe (0.25±0.23 m/sec vs. 0.85±1.21 m/sec, P<0.001 in the same group). The SWV values measured when using the muscle as a standoff material were lower than those without the muscle (significant for 9L4, P=0.040). The deviation from the reference value and the variance increased significantly with the 9L4 probe if the muscle was in situ (B=0.27, P=0.004 and B=0.32, P<0.001). In our study, the pressure exerted by the operator had no effect on the SWV values. Conclusion: The presence of porcine muscle acting as a standoff material influenced the occurrence of failed measurements as well as the variance and the accuracy of the measured values. The linear high-frequency probe was particularly affected.
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Distinct deep subsurface microbial communities in two sandstone units separated by a mudstone layer
Adriana Giongo,Taiana Haag,Renata Medina-Silva,Roberto Heemann,Leandro M. Pereira,Priscilla M. Zamberlan,Fernanda P. Valdez,Rafael R. Oliveira,Eduardo Eizirik,Adriano R. Viana,João Marcelo M. Ketzer 한국지질과학협의회 2020 Geosciences Journal Vol.24 No.3
Deep subsurface microbial communities are more abundant in coarse-grained sedimentary rocks such as sandstones than in fine-grained mudstones. The low porosity and low permeability of mudstones are believed to restrict microbial life. Then, it is expected that distinct, isolated microbial communities may form in sandstones separated by mudstones. In this context, the connectivity between microbial communities in different sandstone units can be investigated to infer evolutionary patterns of diversification in space-time, which may potentially contribute with relevant data for analyses of hydraulic connectivity and stratigraphic correlation. In this work, we used high throughput DNA sequencing of a ribosomal 16S gene fragment to characterize the prokaryotic communities found in Permian sandstone samples of the same core that are separated by one mudstone interval, in the Charqueadas coal field, Parana Basin (Southern Brazil). Our samples were collected at ~300 m deep, in porous sandstones separated by a thick mudstone package. Differences in the bacterial community structure between samples were observed for the classified OTUs, from phylum to genus. Molecular biology might be further applied as a possible tool to help to understand the spatial and temporal distribution of depositional facies, and the efficiency of low permeability rocks to compartmentalize reservoirs. Ongoing studies aim to extend the present investigation into further analyses regarding lateral changes in microbial communities present in the same sandstone units.
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Katharina Hollerieth,Bernhard Gaßmann,Stefan Wagenpfeil,Philipp Moog,Minh-Truc Vo-Cong,Uwe Heemann,Konrad Friedrich Stock 대한초음파의학회 2016 ULTRASONOGRAPHY Vol.35 No.4
Purpose: The purpose of this study was to compare the reliability of ultrasound-based shear wave elastography in regions of homogeneous versus heterogeneous elasticity by using two different probes. Methods: Using acoustic radiation force impulse (ARFI) elastography, we measured the shear wave velocity (SWV) in different lesions of an elastography phantom with the convex 4C1 probe and the linear 9L4 probe. The region of interest (ROI) was positioned in such a way that it was partly filled by one of the lesions (0%, 25%, 50%, 75%, and 100%) and partly by the background of the phantom (100%, 75%, 50%, 25%, and 0%, respectively). Results: The success rate was 98.5%. The measured value and the reference value of SWV correlated significantly (r=0.89, P<0.001). Further, a comparison of the two probes revealed that there was no statistical difference in either the mean or the variance values. However, the deviation of SWV from the reference was higher in the case of the 9L4 probe than in the case of the 4C1 probe, both overall and in measurements in which the ROI contained structures of different elasticity (P=0.021 and P=0.002). Taking into account all data, for both probes, we found that there was a greater spread and deviation of the SWV from the reference value when the ROI was positioned in structures having different elastic properties (standard deviation, 0.02±0.01 m/sec vs. 0.04±0.04 m/sec; P=0.010; deviation from the reference value, 0.21±0.12 m/sec vs. 0.38±0.27 m/sec; P=0.050). Conclusion: Quantitative ARFI elastography was achievable in structures of different elasticity; however, the validity and the reliability of the SWV measurements decreased in comparison to those of the measurements performed in structures of homogeneous elasticity. Therefore, a convex probe is preferred for examining heterogeneous structures.
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