scholarly journals Hydrogen Clearance Method for Determining Local Cerebral Blood Flow. I. Spatial Resolution

1986 ◽  
Vol 6 (4) ◽  
pp. 486-491 ◽  
Author(s):  
Rüdiger von Kummer ◽  
Sigrid Herold
Keyword(s):  
White Matter ◽  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Local Cerebral Blood Flow ◽  
Hydrogen Clearance Method ◽  
Significant Difference ◽  
Cat Brain ◽  
The Mean ◽  
Burr Holes ◽  
Hydrogen Clearance

To define the effective spatial resolution of the hydrogen clearance method, serial local CBF (LCBF) measurements were performed at different distances from the cortico–white matter junction of the cat brain. Twenty-five platinum-wire microelectrodes with a sensitive surface of 0.07 mm2 were inserted into the cerebral cortex of three cats through burr holes in the skull and advanced toward the ear-to-ear level in 1- or 0.1-mm steps. Most electrodes passed from high-perfusion regions into low-perfusion areas, indicating that the cortico–white matter junction had been traversed. Whereas within the gray and white matter the LCBF values were fairly constant, a striking decrease of CBF was registered at the cortico–white matter junction. Here the mean LCBF from 12 electrodes showed significant differences in flow between two locations 1 mm apart. On two occasions, a significant difference in CBF was found for locations only 0.1 mm apart. Despite this high spatial resolution, monoexponential clearance curves were detected only in the vicinity of the cortico–white matter junction. It is therefore assumed that factors other than flow might influence H2 clearance.

[14C]iodoantipyrine and microsphere blood flow estimates in cat brain

1987 ◽  
Vol 253 (5) ◽  
pp. H1289-H1297
Author(s):  
F. J. Schuier ◽  
S. C. Jones ◽  
T. Fedora ◽  
M. Reivich
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
White Matter ◽  
Spatial Resolution ◽  
Gray Matter ◽  
Local Cerebral Blood Flow ◽  
Normal Appearance ◽  
Diffusion Limited ◽  
Cat Brain ◽  
Temporal And Spatial

A comparison of local cerebral blood flow estimates with the microsphere and the 4-[N-methyl-14C]iodoantipyrine ([14C]IAP) techniques has been performed in cats. Good correlation of [14C]IAP with microsphere flow estimates in the gray matter was found. In the white matter, however, [14C]IAP flow estimates were consistently lower than microsphere flow estimates. Error analysis of both techniques and comparison with previous studies suggest that peculiarities of white matter arterial vasculature with preferential microsphere accumulation may lead to this discrepancy. Microspheres did not interfere with flow as shown by the normal appearance of subsequent [14C]IAP autoradiograms. The number of microspheres seen on autoradiograms was used for an estimate of microvessels blocked by spheres and found to be negligible. The study also demonstrates that [14C]IAP is not diffusion limited up to the observed flow values of 2 ml.g-1.min-1. Both techniques might be used together for a combination of their respective advantages, which are temporal and spatial resolution for microsphere and [14C]IAP, respectively.

scholarly journals Mini Electrodes on Ablation Catheters: Valuable Addition or Redundant Information?—Insights from a Computational Study

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Stefan Pollnow ◽  
Joachim Greiner ◽  
Tobias Oesterlein ◽  
Eike M. Wülfers ◽  
Axel Loewe ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Computational Study ◽  
First Line ◽  
Curative Therapy ◽  
Spatial Sensitivity ◽  
Linear Lesions ◽  
Significant Difference ◽  
Diagnostic Benefit ◽  
Unipolar Electrograms

Radiofrequency ablation has become a first-line approach for curative therapy of many cardiac arrhythmias. Various existing catheter designs provide high spatial resolution to identify the best spot for performing ablation and to assess lesion formation. However, creation of transmural and nonconducting ablation lesions requires usage of catheters with larger electrodes and improved thermal conductivity, leading to reduced spatial sensitivity. As trade-off, an ablation catheter with integrated mini electrodes was introduced. The additional diagnostic benefit of this catheter is still not clear. In order to solve this issue, we implemented a computational setup with different ablation scenarios. Ourin silicoresults show that peak-to-peak amplitudes of unipolar electrograms from mini electrodes are more suitable to differentiate ablated and nonablated tissue compared to electrograms from the distal ablation electrode. However, in orthogonal mapping position, no significant difference was observed between distal electrode and mini electrodes electrograms in the ablation scenarios. In conclusion, catheters with mini electrodes bring about additional benefit to distinguish ablated tissue from nonablated tissue in parallel position with high spatial resolution. It is feasible to detect conduction gaps in linear lesions with this catheter by evaluating electrogram data from mini electrodes.

Analysis of pure tilt grain boundary in silicon by Fresnel fringe technique

1991 ◽  
Vol 49 ◽  
pp. 1002-1003
Author(s):  
K. Das Chowdhury ◽  
M. J. Kim ◽  
Y. L. Chen ◽  
R. W. Carpenter
Keyword(s):  
Grain Boundary ◽  
Computer Simulations ◽  
Spatial Resolution ◽  
Atomic Structure ◽  
High Spatial Resolution ◽  
Dark Field ◽  
Fringe Contrast ◽  
The Mean ◽  
Tilt Grain Boundary ◽  
Interfacial Films

One of the main emphases of research on interfaces is to characterize them both structurally and chemically. The atomic structure of interfaces and the existence of thin interfacial glassy phases are being investigated mainly by HREM imaging methods. In addition, a few other methods including dark field diffuse imaging and Fresnel Fringe techniques have been developed to identify the interfacial films and quantify their width. Fresnel fringe profiles from the interface images have been used to deduce the mean inner potential of thin interfacial films. In our research the Fresnel fringe contrast behavior of a tilt grain boundary in silicon whose structure and chemistry were previously characterized by HREM and high spatial resolution AEM was analyzed by comparing the experimental Fresnel fringe profiles with computer simulations of these images.

scholarly journals Do Fetal Isolated Mild Venticulomegaly Make Any Difference in Regional ADC Values at Magnetic Resonans Imaging?

2021 ◽  
Author(s):  
Zeynep Ayvat Öcal ◽  
Özgür Öztekin ◽  
Deniz Öztekin
Keyword(s):  
White Matter ◽  
Statistical Significance ◽  
Occipital Lobe ◽  
Brain Regions ◽  
Control Group ◽  
Adc Value ◽  
Significance Level ◽  
Significant Difference ◽  
Adc Values ◽  
The Mean

Objective: Ventriculomegaly may not only develop secondary to a process,but it may also be in the form of isolated ventriculomegaly with no specific reason. MRI is performed to show the presence of accompanying pathologies.In this study, we measured ADC values in mild ventriculomegaly cases and aimed to investigate the role of ADC value measurements in predicting neurological prognosis in isolated mild ventriculomegaly during MRI. Methods: In our study, ADC values were measured of 37 patients detected to be present with mild ventriculomegaly and 17 fetuses in the control group who had no additional central nervous system patology. For the measurement, ROI was placed in differtent brain regions (frontal lobe white matter,occipital lobe white matter, basal ganglia, thalamus, cerebellum and pons). The analysis of the data obtained was performed using the SPSS (20th version) program. MannWhitney U test was applied. Statistical significance level was set as p<0.05. Results: There was no statistically significant difference between the isolated mild ventriculomegaly and the control group in terms of the mean maternal age (p=0.160). Also, no statistically significant difference was observed between the mean gestational age in the ventriculomegaly group and the control group (p=0.890). There was also no statistically significant difference between ADC measurements in different brain regions in the isolated mild ventriculomegaly and the control group (p=0.807). Conclusion: In order to determine the prognosis in isolated mild ventriculomegaly, other quantitative parameters such as ADC measurement, beyond morphological evaluation and diameter measurement should be determined, and also we need more studies comprising more cases in this field.

Surface Imaging of III–V Semiconductors by Reflection Electron Microscopy and Inner Potential Measurements

1982 ◽  
Vol 18 ◽  
Author(s):  
N. Yamamoto ◽  
J. C. H. Spence
Keyword(s):  
Electron Microscopy ◽  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Surface Steps ◽  
Bulk Plasmon ◽  
Reflection Electron Microscopy ◽  
The Mean ◽  
Diffraction Effects ◽  
Electron Energy Loss ◽  
Electron Energy Loss Spectra

Surfaces of two III–V semiconductor materials have been examined at 120 kV by reflection electron microscopy (REM) at high spatial resolution. Surface steps were found to give characteristic contrast due to several diffraction effects, one of which is interference between the Bragg (B) and Bragg–Laue (BL) reflected beam at a step edge. The electron diffraction pattern from a step showed split lines from B and BL reflections, which provides a method of accurately measuring the mean inner potential of these materials. Electron energy loss spectra showed large surface and bulk plasmon peaks which mainly limit the spatial resolution of REM. The penetration depth in REM is given.

scholarly journals The Hydrogen Clearance Method in Assessment of Blood Flow in Cortex, White Matter and Deep Nuclei of Baboons

Stroke ◽  
1973 ◽  
Vol 4 (4) ◽  
pp. 556-567 ◽  
Author(s):  
EMIL PASZTOR ◽  
LINDSAY SYMON ◽  
N. W. C. DORSCH ◽  
NEIL M. BRANSTON
Keyword(s):  
Blood Flow ◽  
White Matter ◽  
Hydrogen Clearance Method ◽  
Hydrogen Clearance
Sign in / Sign up

Export Citation Format

Share Document