AN AUTOMATIC METHOD OF COMPILATION AND MAPPING OF HIGH‐RESOLUTION AEROMAGNETIC DATA

Geophysics ◽  
1971 ◽  
Vol 36 (4) ◽  
pp. 695-716 ◽  
Author(s):  
B. K. Bhattacharyya
Keyword(s):  
High Resolution ◽  
Magnetic Measurements ◽  
High Sensitivity ◽  
Positional Error ◽  
Automatic Method ◽  
Aeromagnetic Data ◽  
Aeromagnetic Survey ◽  
Machine Method ◽  
Flux Gate ◽  
Definition Of

An automatic method has been developed for compilation of digital aeromagnetic data. This method has been applied to the data obtained during a high‐sensitivity aeromagnetic survey over an area in the Precambrian shield of northeastern Ontario in Canada. With this method, all points of intersection between traverse and base lines are determined automatically and adjusted within the limits of positional error for minimizing differences in magnetic values at the intersections. Then the data are corrected for diurnal variation and leveled to tie the magnetic measurements together. Next, the resulting total field values are contoured with a machine method at a scale of 1:25,000. For such a scale, the minimum contour interval that can be used in the present area is two gammas. However, because of the accuracy of the method of compilation, with a larger scale, it is possible to trace one‐gamma contours. The maps thus compiled have been compared with published aeromagnetic maps of data obtained with conventional flux‐gate and proton‐precession magnetometers. The new maps are vastly superior to the old ones for delineating trends, patterns, and fine features of available detailed geological maps. This superiority is mainly due to the excellent definition of small amplitude anomalies, some of only a few gammas in magnitude, on the high‐resolution magnetic maps.

Aeromagnetic survey in central West Greenland: project Aeromag 2001

2002 ◽  
pp. 67-72 ◽  
Author(s):  
Thorkild M. Rasmussen
Keyword(s):  
High Resolution ◽  
Magnetic Measurements ◽  
Geophysical Data ◽  
High Quality ◽  
Aeromagnetic Survey ◽  
Original Series ◽  
West Greenland ◽  
Airborne Measurements ◽  
Geophysical Surveys ◽  
Airborne Geophysical Data

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article. Rasmussen, T. M. (1). Aeromagnetic survey in central West Greenland: project Aeromag 2001. Geology of Greenland Survey Bulletin, 191, 67-72. https://doi.org/10.34194/ggub.v191.5130 The series of government-funded geophysical surveys in Greenland was continued during the spring and summer of 2001 with a regional aeromagnetic survey north of Uummannaq, project Aeromag 2001 (Fig. 1). The survey added about 70 000 line kilometres of high-quality magnetic measurements to the existing database of modern airborne geophysical data from Greenland. This database includes both regional high-resolution aeromagnetic surveys and detailed surveys with combined electromagnetic and magnetic airborne measurements.

On: “An Automatic Method of Compilation and Mapping of High‐Resolution Aeromagnetic Data,” by B. K. Bhattacharyya (GEOPHYSICS, August 1971, p. 695–716)

Geophysics ◽  
1972 ◽  
Vol 37 (3) ◽  
pp. 544-544
Author(s):  
M. S. Reford
Keyword(s):  
High Resolution ◽  
Mineral Exploration ◽  
Automatic Method ◽  
Aeromagnetic Data ◽  
Geologic Mapping ◽  
Valuable Contribution ◽  
Compilation Techniques

The use of high‐resolution aeromagnetic surveys for detailed geologic mapping and mineral exploration is not yet common, nor are the flying and compilation techniques as standardized as those of conventional or lowsensitivity aeromagnetic surveys. Dr. Bhattacharyya has made a valuable contribution by presenting particularly interesting results and describing the techniques in some detail. But there are some points in his comparisons between high‐resolution and conventional surveys which could be misleading.

scholarly journals Project EASTMAR: acquisition of high sensitivity aeromagnetic data off East Greenland

1980 ◽  
Vol 100 ◽  
pp. 91-94
Author(s):  
H.C Larsen ◽  
L Thorning
Keyword(s):  
Continental Margin ◽  
North Atlantic ◽  
High Sensitivity ◽  
Aeromagnetic Data ◽  
Energy Agency ◽  
Aeromagnetic Survey ◽  
East Greenland ◽  
Main Work ◽  
Marine Gravity ◽  
Multichannel Seismic Reflection

Project EASTMAR, an aeromagnetic survey of major parts of the continental margin off East Greenland, is an energy research project originally funded by the Danish government through the Energy Agency (Thorning, 1978; Larsen & Thorning, 1979). During 1979, the EASTMAR project has been included in an EEC supported geophysical project called the NAD project (North Atlantic D; see also Risum, this volume). The aim of the NAD project is to map the deep and regional structures of the continental margin off East Greenland by using high sensitivity aeromagnetic surveys, multichannel seismic reflection and marine gravity surveys, and to prepare a preIiminary assessment of the petroleum geology of the region. In 1979, the main work of EASTMAR has been the acquisition of new aeromagnetic data between latitudes 600 N and 800 N in accordance with the flight programme (fig. 31; and Larsen & Thorning, 1979) and compilation of existing aeromagnetic and seismic data (Larsen, 1980).

Backscattered Electron Imaging of GaAs/AlGaAs Super Lattice Structures with an Ultra-High- Resolution SEM

1988 ◽  
Vol 46 ◽  
pp. 204-205
Author(s):  
Kazumichi Ogura ◽  
Michael M. Kersker
Keyword(s):  
High Resolution ◽  
Layer Structure ◽  
High Sensitivity ◽  
Beam Current ◽  
Electron Beam Current ◽  
Lattice Structures ◽  
Super Lattice ◽  
Different Types ◽  
Backscattered Electron ◽  
Electron Imaging

Backscattered electron (BE) images of GaAs/AlGaAs super lattice structures were observed with an ultra high resolution (UHR) SEM JSM-890 with an ultra high sensitivity BE detector. Three different types of super lattice structures of GaAs/AlGaAs were examined. Each GaAs/AlGaAs wafer was cleaved by a razor after it was heated for approximately 1 minute and its crosssectional plane was observed.First, a multi-layer structure of GaAs (100nm)/AlGaAs (lOOnm) where A1 content was successively changed from 0.4 to 0.03 was observed. Figures 1 (a) and (b) are BE images taken at an accelerating voltage of 15kV with an electron beam current of 20pA. Figure 1 (c) is a sketch of this multi-layer structure corresponding to the BE images. The various layers are clearly observed. The differences in A1 content between A1 0.35 Ga 0.65 As, A1 0.4 Ga 0.6 As, and A1 0.31 Ga 0.69 As were clearly observed in the contrast of the BE image.

scholarly journals BIMG-04. MAPPING HETEROGENEITY OF HIGH-GRADE GLIOMA METABOLISM USING HIGH RESOLUTION 7T MRSI

2021 ◽  
Vol 3 (Supplement_1) ◽  
pp. i1-i1
Author(s):  
Gilbert Hangel ◽  
Cornelius Cadrien ◽  
Philipp Lazen ◽  
Sukrit Sharma ◽  
Julia Furtner ◽  
...  
Keyword(s):  
High Resolution ◽  
Imaging Techniques ◽  
Basis Set ◽  
Metabolic Imaging ◽  
Tumor Segmentation ◽  
Low Grade ◽  
High Grade ◽  
Isotropic Resolution ◽  
Contrast Enhanced ◽  
Definition Of

Abstract OBJECTIVES Neurosurgical resection in gliomas depends on the precise preoperative definition of the tumor and its margins to realize a safe maximum resection that translates into a better patient outcome. New metabolic imaging techniques could improve this delineation as well as designate targets for biopsies. We validated the performance of our fast high-resolution whole-brain 3D-magnetic resonance spectroscopic imaging (MRSI) method at 7T in high-grade gliomas (HGGs) as first step to this regard. METHODS We measured 23 patients with HGGs at 7T with MRSI covering the whole cerebrum with 3.4mm isotropic resolution in 15 min. Quantification used a basis-set of 17 neurochemical components. They were evaluated for their reliability/quality and compared to neuroradiologically segmented tumor regions-of-interest (necrosis, contrast-enhanced, non-contrast-enhanced+edema, peritumoral) and histopathology (e.g., grade, IDH-status). RESULTS We found 18/23 measurements to be usable and ten neurochemicals quantified with acceptable quality. The most common denominators were increases of glutamine, glycine, and total choline as well as decreases of N-acetyl-aspartate and total creatine over most tumor regions. Other metabolites like taurine and serine showed mixed behavior. We further found that heterogeneity in the metabolic images often continued into the peritumoral region. While 2-hydroxy-glutarate could not be satisfyingly quantified, we found a tendency for a decrease of glutamate in IDH1-mutant HGGs. DISCUSSION Our findings corresponded well to clinical tumor segmentation but were more heterogeneous and often extended into the peritumoral region. Our results corresponded to previous knowledge, but with previously not feasible resolution. Apart from glycine/glutamine and their role in glioma progression, more research on the connection of glutamate and others to specific mutations is necessary. The addition of low-grade gliomas and statistical ROI analysis in a larger cohort will be the next important steps to define the benefits of our 7T MRSI approach for the definition of spatial metabolic tumor profiles.

Ex Vivo assessment of competent strut coverage after coronary stenting by optical coherence tomography

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
R Bhoite ◽  
H Jinnouchi ◽  
F Otsuka ◽  
Y Sato ◽  
A Sakamoto ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Predictive Value ◽  
Ex Vivo ◽  
High Sensitivity ◽  
Optical Coherence ◽  
Cross Sectional ◽  
Neointimal Thickness ◽  
Stent Strut ◽  
Oct Imaging ◽  
Definition Of

Abstract Background In many studies, struts coverage is defined as >0 mm of tissue overlying the stent struts by optical coherence tomography (OCT). However, this definition has never been validated using histology as the “gold standard”. The present study sought to assess the appropriate cut-off value of neointimal thickness of stent strut coverage by OCT using histology. Methods OCT imaging was performed on 39 human coronary arteries with stents from 25 patients at autopsy. A total of 165 cross-sectional images from 46 stents were co-registered with histology. The optimal cut-off value of strut coverage by OCT was determined. Strut coverage by histology was defined as endothelial cells with at least underlying two layers of smooth muscle cells. Considering the resolution of OCT is 10–20 μm, 3 different cut-off values (i.e. at ≥20, ≥40, and ≥60 μm) were assessed. Results A total of 2235 struts were evaluated by histology. Eventually, 1216 struts which were well-matched struts were analyzed in this study. By histology, uncovered struts were observed in 160 struts and covered struts were observed in 1056 struts. The broadly used definition of OCT-coverage which does not consider neointimal thickness yielded a poor specificity of 37.5% and high sensitivity 100%. Of 3 cut-off values, the cut-off value of >40 μm was more accurate as compared to >20 and >60 mm [sensitivity (99.3%), specificity (91.0%), positive predictive value (98.6%), and negative predictive value (95.6%)] Conclusion The most accurate cut-off value was ≥40 μm neointimal thickness by OCT in order to identify stent strut coverage validated by histology. Funding Acknowledgement Type of funding source: None

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