Improvements in the Analysis of Ultrasonic Scattering from Inhomogeneities in Tissue

1979 ◽  
Vol 1 (1) ◽  
pp. 44-55 ◽  
Author(s):  
S. Ø. Aks ◽  
D. J. Vezzetti
Keyword(s):  
Scattering Theory ◽  
Limited Range ◽  
Ultrasonic Scattering ◽  
Sample Geometry ◽  
Realistic Choice

The elementary scattering theory of Rayleigh and Born is extended to account for effects of finite absorption and of sample geometry including boundary refraction. Examples of the procedure are given for several scatterer configurations and results compared with those of the Rayleigh-Born procedure. It is shown that for a realistic choice of tissue parameters these effects modify the Rayleigh-Born results by factors of the order of 10 percent or less provided observations are made over a suitably limited range of angles about the backward direction.

Ultrasonic Scattering Theory II: Scattering from Composites

1980 ◽  
Vol 2 (3) ◽  
pp. 195-212 ◽  
Author(s):  
D. J. Vezzetti ◽  
S. Ø. Aks
Keyword(s):  
Scattering Theory ◽  
Tissue Characterization ◽  
Ultrasonic Waves ◽  
Index Of Refraction ◽  
Ultrasonic Scattering

This is the second of two papers which present the fundamental concepts and terminology of acoustical scattering theory in a manner suitable for use by those involved in ultrasonic tissue characterization. The first paper [1] dealt with scattering by single objects. The present paper discusses scattering by collections of objects, including statistical aspects of scattering and the theory of the index of refraction for ultrasonic waves.

Ultrasonic Scattering Theory. I: Scattering by Single Objects

1980 ◽  
Vol 2 (2) ◽  
pp. 85-101 ◽  
Author(s):  
S. Ø. Aks ◽  
D. J. Vezzetti
Keyword(s):  
Scattering Theory ◽  
Tissue Characterization ◽  
Future Issue ◽  
Ultrasonic Scattering

This is the first of two papers which present the fundamental concepts and terminology of acoustical scattering theory in a manner suitable for use by those involved in ultrasonic tissue characterization. This first paper deals with scattering by single objects and the second, which will appear in a future issue, with scattering by collection of objects.

scholarly journals Experimental Analysis of Ultrasonic Multiple Scattering Attenuation through the Air with Fine Dust

2021 ◽  
Vol 11 (2) ◽  
pp. 694
Author(s):  
Ukyong Woo ◽  
Hajin Choi ◽  
Homin Song
Keyword(s):  
Signal Processing ◽  
Multiple Scattering ◽  
Cross Section ◽  
Approximation Theory ◽  
Experimental Analysis ◽  
Scattering Theory ◽  
Ultrasonic Attenuation ◽  
Fine Dust ◽  
Ultrasonic Scattering ◽  
Scattering Attenuation

In this study, we experimentally evaluated the application of multiple scattering theory for measuring ultrasonic attenuation. Based on the independent approximation theory, the method adopted for calculating the attenuation of coherent waves through air with fine dust is discussed. To obtain a scattering wavefield, a unique ultrasonic scattering hardware was developed, and signal processing schemes were suggested. Four cases of standard particle doses (0, 0.004, 0.008, and 0.012 g) were investigated inside a chamber. The results obtained from the experiments demonstrate that the proposed signal processing approach successfully calculates the scattering attenuation, which correlates well with the applied doses of fine dust. In addition, we discuss the irregular shape and composition of fine dust relative to the scattering cross-section.

Southern Hemisphere Seti Survey: Five Years of Project Meta II

1997 ◽  
Vol 161 ◽  
pp. 611-621
Author(s):  
Guillermo A. Lemarchand ◽  
Fernando R. Colomb ◽  
E. Eduardo Hurrell ◽  
Juan Carlos Olalde
Keyword(s):  
Southern Hemisphere ◽  
Scattering Theory ◽  
Galactic Plane ◽  
Narrow Band ◽  
Neutral Hydrogen ◽  
Sky Survey ◽  
Inertial Frames ◽  
Interstellar Scattering ◽  
Extraterrestrial Origin ◽  
Spectral Channels

AbstractProject META II, a full sky survey for artificial narrow-band signals, has been conducted from one of the two 30-m radiotelescopes of the Instituto Argentino de Radioastronomía (IAR). The search was performed near the 1420 Mhz line of neutral hydrogen, using a 8.4 million channels Fourier spectrometer of 0.05 Hz resolution and 400 kHz instantaneous bandwidth. The observing frequency was corrected both for motions with respect to three astronomical inertial frames, and for the effect of Earths rotation, which provides a characteristic changing signature for narrow-band signals of extraterrestrial origin. Among the 2 × 1013spectral channels analyzed, 29 extra-statistical narrow-band events were found, exceeding the average threshold of 1.7 × 10−23Wm−2. The strongest signals that survive culling for terrestrial interference lie in or near the galactic plane. A description of the project META II observing scheme and results is made as well as the possible interpretation of the results using the Cordes-Lazio-Sagan model based in interstellar scattering theory.

New polarized-light microscope for fast and orientation independent measurement of birefringent fine structure

1993 ◽  
Vol 51 ◽  
pp. 82-83
Author(s):  
Rudolf Oldenbourg
Keyword(s):  
Light Microscope ◽  
Polarized Light ◽  
Video Camera ◽  
Limited Range ◽  
Image Point ◽  
Computer Assisted ◽  
Optical Modulators ◽  
Anisotropic Structures ◽  
Long Time ◽  
Computer Assisted Image

The polarized light microscope has the unique potential to measure submicroscopic molecular arrangements dynamically and non-destructively in living cells and other specimens. With the traditional pol-scope, however, single images display only those anisotropic structures that have a limited range of orientations with respect to the polarization axes of the microscope. Furthermore, rapid measurements are restricted to a single image point or single area that exhibits uniform birefringence or other form of optical anisotropy, while measurements comparing several image points take an inordinately long time.We are developing a new kind of polarized light microscope which combines speed and high resolution in its measurement of the specimen anisotropy, irrespective of its orientation. The design of the new pol-scope is based on the traditional polarized light microscope with two essential modifications: circular polarizers replace linear polarizers and two electro-optical modulators replace the traditional compensator. A video camera and computer assisted image analysis provide measurements of specimen anisotropy in rapid succession for all points of the image comprising the field of view.

Dynamical Scattering in Electron Diffraction of wet Protein Crystals

1980 ◽  
Vol 38 ◽  
pp. 42-43
Author(s):  
B. B. Chang ◽  
D. F. Parsons
Keyword(s):  
Electron Diffraction ◽  
Scattering Theory ◽  
Protein Crystals ◽  
Electron Diffraction Data ◽  
Specimen Thickness ◽  
Major Question ◽  
X Ray ◽  
Scattering Effects ◽  
Diffraction Patterns ◽  
Acceleration Voltage

The significance of dynamical scattering effects remains the major question in the structural analysis by electron diffraction of protein crystals preserved in the hydrated state. In the few cases (single layers of purple membrane and 400-600 Å thick catalase crystals examined at 100 kV acceleration voltage) where electron-diffraction patterns were used quantitatively, dynamical scattering effects were considered unimportant on the basis of a comparison with x-ray intensities. The kinematical treatment is usually justified by the thinness of the crystal. A theoretical investigation by Ho et al. using Cowley-Moodie multislice formulation of dynamical scattering theory and cytochrome b5as the test object2 suggests that kinematical analysis of electron diffraction data with 100-keV electrons would not likely be valid for specimen thickness of 300 Å or more. We have chosen to work with electron diffraction patterns obtained from actual wet protein crystals (rat hemoglobin crystals of thickness range 1000 to 2500 Å) at 200 and 1000 kV and to analyze these for dynamical effects.

Impairment Tutorial: Rating Tears of the Acetabular Labrum

2006 ◽  
Vol 11 (6) ◽  
pp. 4-7
Author(s):  
Charles N. Brooks ◽  
Richard E. Strain ◽  
James B. Talmage
Keyword(s):  
Magnetic Resonance ◽  
Hip Arthroscopy ◽  
Age Groups ◽  
Limited Range ◽  
Labral Repair ◽  
X Rays ◽  
Joint Stability ◽  
Acetabular Labrum ◽  
Complete Excision ◽  
Limited Range Of Motion

Abstract The primary function of the acetabular labrum, like that of the glenoid, is to deepen the socket and improve joint stability. Tears of the acetabular labrum are common in older adults but occur in all age groups and with equal frequency in males and females. The AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Fifth Edition, is silent about rating tears, partial or complete excision, or repair of the acetabular labrum. Provocative tests to detect acetabular labrum tears involve hip flexion and rotation; all rely on production of pain in the groin (typically), clicking, and/or locking with passive or active hip motions. Diagnostic tests or procedures rely on x-rays, conventional arthrography, computerized tomography, magnetic resonance imaging (MRI), magnetic resonance arthrography (MRA), and hip arthroscopy. Hip arthroscopy is the gold standard for diagnosis but is the most invasive and most likely to result in complications, and MRA is about three times more sensitive and accurate in detecting acetabular labral tears than MRI alone. Surgical treatment for acetabular labrum tears usually consists of arthroscopic debridement; results tend to be better in younger patients. In general, an acetabular labral tear, partial labrectomy, or labral repair warrants a rating of 2% lower extremity impairment. Evaluators should avoid double dipping (eg, using both a Diagnosis-related estimates and limited range-of-motion tests).

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