Photon migration in upscaled tissue models: measurements and Monte Carlo simulations

1993 ◽  
Author(s):  
Frits F. M. de Mul ◽  
Marco H. Koelink ◽  
M. Kok ◽  
Jan Greve ◽  
Reindert Graaff ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Photon Migration ◽  
Tissue Models

Sampling of time- and frequency-domain signals in Monte Carlo simulations of photon migration

1999 ◽  
Vol 38 (1) ◽  
pp. 236 ◽  
Author(s):  
Markus Testorf ◽  
Ulf Österberg ◽  
Brian Pogue ◽  
Keith Paulsen
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Frequency Domain ◽  
Photon Migration

Visible-light photon migration through myocardium in vivo

1999 ◽  
Vol 277 (2) ◽  
pp. H698-H704 ◽  
Author(s):  
Amir H. Gandjbakhche ◽  
Robert F. Bonner ◽  
Andrew E. Arai ◽  
Robert S. Balaban
Keyword(s):  
Monte Carlo ◽  
Cytochrome C ◽  
Monte Carlo Simulations ◽  
Heart Tissue ◽  
Integrating Sphere ◽  
Photon Migration ◽  
Spectral Features ◽  
Absorption Coefficients ◽  
Reflected Light

Empirical data between 510 and 590 nm of diffuse reflected light from the pig heart in vivo have shown that myoglobin and cytochrome c absorption peaks with little apparent contribution of red blood cell (RBC) Hb. Monte Carlo simulations of photon migration in tissue were performed to compare the effects of myoglobin and cytochromes with those of blood Hb on photon pathlengths and diffuse reflectance of visible wavelengths (450–600 nm) from the pig heart in vivo. Wavelength dependence of the input parameters, including the transport-corrected scattering coefficients (1.1–1.2 mm−1) and the absorption coefficients of blood-free solubilized heart tissue (0.43–1.47 mm−1), as well as the absorption coefficients of Hb, were determined by an integrating sphere method and standard spectrophotometry, respectively. The Monte Carlo simulations indicate that in the 510- to 590-nm range the mean path length within the myocardium for diffusely reflected light varies from 1.4 to 1.2 mm, whereas their mean penetration depth within the epicardium is only 330–400 μm for blood-free heart tissue. Analysis shows that the blood Hb absorption extrema are only observable between 510 and 590 nm when RBC concentration in tissue is >0.5%. Blood within vessels much larger than capillaries does not contribute significantly to the spectral features, because virtually all light in this spectral range is absorbed during transit through large vessels (>100 μm). This analysis suggests that diffuse reflected light in the 510- to 590-nm region will show spectral features uniquely associated with myoglobin and cytochrome c oxygenation states within 400 μm of the surface of the heart in situ as long as the capillary RBC concentration remains <0.5%.

Low-voltage EDS of magnesium ferrite Dendrites in a FEG-SEM

1996 ◽  
Vol 54 ◽  
pp. 478-479
Author(s):  
Matthew T. Johnson ◽  
Ian M. Anderson ◽  
Jim Bentley ◽  
C. Barry Carter
Keyword(s):  
Monte Carlo ◽  
Quantitative Analysis ◽  
Monte Carlo Simulations ◽  
Cross Section ◽  
Spatial Resolution ◽  
Low Voltage ◽  
Magnesium Ferrite ◽  
X Ray ◽  
Interaction Volume ◽  
Ferrite Spinel

Energy-dispersive X-ray spectrometry (EDS) performed at low (≤ 5 kV) accelerating voltages in the SEM has the potential for providing quantitative microanalytical information with a spatial resolution of ∼100 nm. In the present work, EDS analyses were performed on magnesium ferrite spinel [(MgxFe1−x)Fe2O4] dendrites embedded in a MgO matrix, as shown in Fig. 1. spatial resolution of X-ray microanalysis at conventional accelerating voltages is insufficient for the quantitative analysis of these dendrites, which have widths of the order of a few hundred nanometers, without deconvolution of contributions from the MgO matrix. However, Monte Carlo simulations indicate that the interaction volume for MgFe2O4 is ∼150 nm at 3 kV accelerating voltage and therefore sufficient to analyze the dendrites without matrix contributions.Single-crystal {001}-oriented MgO was reacted with hematite (Fe2O3) powder for 6 h at 1450°C in air and furnace cooled. The specimen was then cleaved to expose a clean cross-section suitable for microanalysis.

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