scholarly journals Virtual Breast Quasi-static Elastography (VBQE)

2016 ◽  
Vol 39 (2) ◽  
pp. 108-125 ◽  
Author(s):  
David Rosen ◽  
Yu Wang ◽  
Jingfeng Jiang
Keyword(s):  
Relaxation Time ◽  
Three Dimensional ◽  
Primary Objective ◽  
Transfer Efficiency ◽  
External Compression ◽  
Time Resolved ◽  
Time Constants ◽  
Strain Measurements ◽  
Relaxation Time Constants

Viscoelasticity Imaging (VEI) has been proposed to measure relaxation time constants for characterization of in vivo breast lesions. In this technique, an external compression force on the tissue being imaged is maintained for a fixed period of time to induce strain creep. A sequence of ultrasound echo signals is then utilized to generate time-resolved strain measurements. Relaxation time constants can be obtained by fitting local time-resolved strain measurements to a viscoelastic tissue model (e.g., a modified Kevin-Voigt model). In this study, our primary objective is to quantitatively evaluate the contrast transfer efficiency (CTE) of VEI, which contains useful information regarding image interpretations. Using an open-source simulator for virtual breast quasi-static elastography (VBQE), we conducted a case study of contrast transfer efficiency of VEI. In multiple three-dimensional (3D) numerical breast phantoms containing various degrees of heterogeneity, finite element (FE) simulations in conjunction with quasi-linear viscoelastic constitutive tissue models were performed to mimic data acquisition of VEI under freehand scanning. Our results suggested that there were losses in CTE, and the losses could be as high as −18 dB. FE results also qualitatively corroborated clinical observations, for example, artifacts around tissue interfaces.

scholarly journals Transverse relaxation time constants of the five major metabolites in human brain measured in vivo using LASER and PRESS at 3 T

2017 ◽  
Vol 79 (3) ◽  
pp. 1260-1265 ◽  
Author(s):  
Dinesh K. Deelchand ◽  
Edward J. Auerbach ◽  
Naoharu Kobayashi ◽  
Małgorzata Marjańska
Keyword(s):  
Relaxation Time ◽  
Human Brain ◽  
Transverse Relaxation Time ◽  
Transverse Relaxation ◽  
Time Constants ◽  
Relaxation Time Constants

Local, Three-Dimensional Strain Measurements Within Largely Deformed Extracellular Matrix Constructs

2004 ◽  
Vol 126 (6) ◽  
pp. 699-708 ◽  
Author(s):  
Blayne A. Roeder ◽  
Klod Kokini ◽  
J. Paul Robinson ◽  
Sherry L. Voytik-Harbin
Keyword(s):  
Extracellular Matrix ◽  
Local Level ◽  
Three Dimensional ◽  
Collagen Matrices ◽  
Mechanical Loads ◽  
Strain Measurements ◽  
3D Collagen ◽  
Vitro Model

The ability to create extracellular matrix (ECM) constructs that are mechanically and biochemically similar to those found in vivo and to understand how their properties affect cellular responses will drive the next generation of tissue engineering strategies. To date, many mechanisms by which cells biochemically communicate with the ECM are known. However, the mechanisms by which mechanical information is transmitted between cells and their ECM remain to be elucidated. “Self-assembled” collagen matrices provide an in vitro-model system to study the mechanical behavior of ECM. To begin to understand how the ECM and the cells interact mechanically, the three-dimensional (3D) mechanical properties of the ECM must be quantified at the micro-(local) level in addition to information measured at the macro-(global) level. Here we describe an incremental digital volume correlation (IDVC) algorithm to quantify large (>0.05) 3D mechanical strains in the microstructure of 3D collagen matrices in response to applied mechanical loads. Strain measurements from the IDVC algorithm rely on 3D confocal images acquired from collagen matrices under applied mechanical loads. The accuracy and the precision of the IDVC algorithm was verified by comparing both image volumes collected in succession when no deformation was applied to the ECM (zero strain) and image volumes to which simulated deformations were applied in both 1D and 3D (simulated strains). Results indicate that the IDVC algorithm can accurately and precisely determine the 3D strain state inside largely deformed collagen ECMs. Finally, the usefulness of the algorithm was demonstrated by measuring the microlevel 3D strain response of a collagen ECM loaded in tension.

Thermal equilibration of samples for neutron scattering

2013 ◽  
Vol 46 (1) ◽  
pp. 279-285 ◽  
Author(s):  
Tobias K. Herman ◽  
Sarah C. Parks ◽  
Julia Scherschligt
Keyword(s):  
Relaxation Time ◽  
Neutron Scattering ◽  
Material Properties ◽  
Thermal Relaxation ◽  
Sample Cell ◽  
Time Constants ◽  
Thermal Equilibration ◽  
Temperature Relaxation ◽  
Relaxation Time Constants ◽  
Selection Of

Temperature relaxation and equilibration of samples for neutron scattering was investigated in a selection of samples and sample cells within the range of 5–300 K. A simple model was developed that relates thermal relaxation time constants to material properties of the sample and sample cell. This model should facilitate extension of this study to prediction of thermal behavior in other systems.

In vivo and in vitro validation of aortic flow quantification by time-resolved three-dimensional velocity-encoded MRI

2012 ◽  
Vol 28 (8) ◽  
pp. 1999-2008 ◽  
Author(s):  
Fabian Rengier ◽  
Michael Delles ◽  
Roland Unterhinninghofen ◽  
Sebastian Ley ◽  
Matthias Müller-Eschner ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Aortic Flow ◽  
Flow Quantification ◽  
Time Resolved

scholarly journals Time-resolved analyses of elemental distribution and concentration in living plants: An example using manganese toxicity in cowpea leaves

2017 ◽  
Author(s):  
F. Pax C. Blamey ◽  
David J. Paterson ◽  
Adam Walsh ◽  
Nader Afshar ◽  
Brigid A. McKenna ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Plant Tissues ◽  
Elemental Distribution ◽  
List Type ◽  
Time Resolved ◽  
Living Plant ◽  
Xrf Scanning ◽  
Leaf Tissues ◽  
Changes Over Time

SummaryKnowledge of elemental distribution and concentration within plant tissues is crucial in the understanding of almost every process that occurs within plants. However, analytical limitations have hindered the microscopic determination of changes over time in the location and concentration of nutrients and contaminants in living plant tissues.We developed a novel method using synchrotron-based micro X-ray fluorescence (μ-XRF) that allows for laterally-resolved, multi-element, kinetic analyses of plant leaf tissues in vivo. To test the utility of this approach, we examined changes in the accumulation of Mn in unifoliate leaves of 7-d-old cowpea (Vigna unguiculata) plants grown for 48 h at 0.2 and 30 μM Mn in solution.Repeated μ-XRF scanning did not damage leaf tissues demonstrating the validity of the method. Exposure to 30 μM Mn for 48 h increased the initial number of small spots of localized high Mn and their concentration rose from 40 to 670 mg Mn kg-1 fresh mass. Extension of the two-dimensional μ-XRF scans to a three-dimensional geometry provided further assessment of Mn localization and concentration.This method shows the value of synchrotron-based μ-XRF analyses for time-resolved in vivo analysis of elemental dynamics in plant sciences.

Interpretation of relaxation time constants for amorphous pharmaceutical systems

2000 ◽  
Vol 89 (3) ◽  
pp. 417 ◽  
Author(s):  
Sheri L. Shamblin ◽  
Bruno C. Hancock ◽  
Yves Dupuis ◽  
Michael J. Pikal
Keyword(s):  
Relaxation Time ◽  
Time Constants ◽  
Relaxation Time Constants
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