101
|
Tian L, Wei H, Jin Y, Liu H, Guo Z, Deng X. Backward emission angle of microscopic second-harmonic generation from crystallized type I collagen fiber. JOURNAL OF BIOMEDICAL OPTICS 2011; 16:075001. [PMID: 21806258 DOI: 10.1117/1.3596174] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
A theoretical model that deals with SHG from crystallized type I collagen fiber formed by a bundle of fibrils is established. By introducing a density distribution function of dipoles within fibrils assembly into the dipole theory and combining with structural order (m,l) parameters revealed by quasi-phase-matching (QPM) theory, our established theoretical model comprehensively characterizes both biophysical features of collagen dipoles and the crystalline characteristics of collagen fiber. This new model quantitatively reveals the 3-D distribution of second-harmonic generation (SHG) emission angle (θ,ϕ) in accordance with the emission power. Results show that fibrils diameter d(1) and structural order m, which describes the structural characteristics of collagen fiber along the incident light propagation direction has significant influence on backward∕forward SHG emission. The decrease of fibrils diameter d(1) induces an increase of the peak SHG emission angle θ(max). As d(1) decreases to a threshold value, in our case it is around d(1) = 150 nm when (m,l) = (1,0), θ(max) > 90 deg, indicating that backward SHG emission appears. The SHG may have two symmetrical emission distribution lobes or may have only one or two unsymmetrical emission lobes with unequal emission power, depending on the functional area of (m,l) on d(1).
Collapse
Affiliation(s)
- Long Tian
- South China Normal University, MOE Key Laboratory of Laser Life Science, Tianhe Shipai, Guangzhou, Guangzhou 510631 China
| | | | | | | | | | | |
Collapse
|
102
|
Goulam Houssen Y, Gusachenko I, Schanne-Klein MC, Allain JM. Monitoring micrometer-scale collagen organization in rat-tail tendon upon mechanical strain using second harmonic microscopy. J Biomech 2011; 44:2047-52. [PMID: 21636086 DOI: 10.1016/j.jbiomech.2011.05.009] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Revised: 05/04/2011] [Accepted: 05/06/2011] [Indexed: 11/30/2022]
Abstract
We continuously monitored the microstructure of a rat-tail tendon during stretch/relaxation cycles. To that purpose, we implemented a new biomechanical device that combined SHG imaging and mechanical testing modalities. This multi-scale experimental device enabled simultaneous visualization of the collagen crimp morphology at the micrometer scale and measurement of macroscopic strain-stress response. We gradually increased the ultimate strain of the cycles and showed that preconditioning mostly occurs in the first stretching. This is accompanied by an increase of the crimp period in the SHG image. Our results indicate that preconditioning is due to a sliding of microstructures at the scale of a few fibrils and smaller, that changes the resting length of the fascicle. This sliding can reverse on long time scales. These results provide a proof of concept that continuous SHG imaging performed simultaneously with mechanical assay allows analysis of the relationship between macroscopic response and microscopic structure of tissues.
Collapse
Affiliation(s)
- Y Goulam Houssen
- Ecole Polytechnique, Laboratory for Optics and Biosciences, 91128 Palaiseau, France
| | | | | | | |
Collapse
|
103
|
Abstract
Second Harmonic Generation microscopy has emerged as a powerful new optical imaging modality. This Feature describes its chemical and physical principles and highlights current applications in disease diagnostics.
Collapse
|
104
|
Gualtieri EJ, Guo F, Kissick DJ, Jose J, Kuhn RJ, Jiang W, Simpson GJ. Detection of membrane protein two-dimensional crystals in living cells. Biophys J 2011; 100:207-14. [PMID: 21190673 DOI: 10.1016/j.bpj.2010.10.051] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2010] [Revised: 10/14/2010] [Accepted: 10/18/2010] [Indexed: 12/11/2022] Open
Abstract
It is notoriously difficult to grow membrane protein crystals and solve membrane protein structures. Improved detection and screening of membrane protein crystals are needed. We have shown here that second-order nonlinear optical imaging of chiral crystals based on second harmonic generation can provide sensitive and selective detection of two-dimensional protein crystalline arrays with sufficiently low background to enable crystal detection within the membranes of live cells. The method was validated using bacteriorhodopsin crystals generated in live Halobacterium halobium bacteria and confirmed by electron microscopy from the isolated crystals. Additional studies of alphavirus glycoproteins indicated the presence of localized crystalline domains associated with virus budding from mammalian cells. These results suggest that in vivo crystallization may provide a means for expediting membrane protein structure determination for proteins exhibiting propensities for two-dimensional crystal formation.
Collapse
Affiliation(s)
- E J Gualtieri
- Department of Chemistry, Department of Biological Sciences, Purdue University, West Lafayette, Indiana, USA
| | | | | | | | | | | | | |
Collapse
|
105
|
Kissick DJ, Wanapun D, Simpson GJ. Second-order nonlinear optical imaging of chiral crystals. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2011; 4:419-37. [PMID: 21469954 PMCID: PMC3345893 DOI: 10.1146/annurev.anchem.111808.073722] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Second-order nonlinear optical imaging of chiral crystals (SONICC) is an emerging technique for crystal imaging and characterization. We provide a brief overview of the origin of second harmonic generation signals in SONICC and discuss recent studies using SONICC for biological applications. Given that they provide near-complete suppression of any background, SONICC images can be used to determine the presence or absence of protein crystals through both manual inspection and automated analysis. Because SONICC creates high-resolution images, nucleation and growth kinetics can also be observed. SONICC can detect metastable, homochiral crystalline forms of amino acids crystallizing from racemic solutions, which confirms Ostwald's rule of stages for crystal growth. SONICC's selectivity, based on order, and sensitivity, based on background suppression, make it a promising technique for numerous fields concerned with chiral crystal formation.
Collapse
Affiliation(s)
- David J Kissick
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA.
| | | | | |
Collapse
|
106
|
Rivard M, Laliberté M, Bertrand-Grenier A, Harnagea C, Pfeffer CP, Vallières M, St-Pierre Y, Pignolet A, El Khakani MA, Légaré F. The structural origin of second harmonic generation in fascia. BIOMEDICAL OPTICS EXPRESS 2010; 2:26-36. [PMID: 21326632 PMCID: PMC3028495 DOI: 10.1364/boe.2.000026] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2010] [Revised: 11/16/2010] [Accepted: 11/29/2010] [Indexed: 05/18/2023]
Abstract
Fascia tissue is rich in collagen type I proteins and can be imaged by second harmonic generation (SHG) microscopy. While identifying the overall alignment of the collagen fibrils is evident from those images, the tridimensional structural origin for the observation of SHG signal is more complex than it apparently seems. Those images reveal that the noncentrosymmetric (piezoelectric) structures are distributed heterogeneously on spatial dimensions inferior to the resolution provided by the nonlinear optical microscope (sub-micron). Using piezoresponse force microscopy (PFM), we show that an individual collagen fibril has a noncentrosymmetric structural organization. Fibrils are found to be arranged in nano-domains where the anisotropic axis is preserved along the fibrillar axis, while across the collagen sheets, the phase of the second order nonlinear susceptibility is changing by 180 degrees between adjacent nano-domains. This complex architecture of noncentrosymmetric nano-domains governs the coherent addition of 2ω light within the focal volume and the observed features in the SHG images taken in fascia.
Collapse
Affiliation(s)
- Maxime Rivard
- Institut National de la Recherche Scientifique, Centre Énergie Matériaux et Télécommunications, 1650 Boulevard Lionel-Boulet, Varennes, Qc Canada J3X1S2
| | - Mathieu Laliberté
- Institut National de la Recherche Scientifique, Centre Énergie Matériaux et Télécommunications, 1650 Boulevard Lionel-Boulet, Varennes, Qc Canada J3X1S2
| | - Antony Bertrand-Grenier
- Institut National de la Recherche Scientifique, Centre Énergie Matériaux et Télécommunications, 1650 Boulevard Lionel-Boulet, Varennes, Qc Canada J3X1S2
| | - Catalin Harnagea
- Institut National de la Recherche Scientifique, Centre Énergie Matériaux et Télécommunications, 1650 Boulevard Lionel-Boulet, Varennes, Qc Canada J3X1S2
| | | | - Martin Vallières
- Institut National de la Recherche Scientifique, Centre Énergie Matériaux et Télécommunications, 1650 Boulevard Lionel-Boulet, Varennes, Qc Canada J3X1S2
| | - Yves St-Pierre
- Institut National de la Recherche Scientifique, Institut Armand-Frappier, 531 boul. des Prairies, Laval, Qc Canada H7V 1B7
| | - Alain Pignolet
- Institut National de la Recherche Scientifique, Centre Énergie Matériaux et Télécommunications, 1650 Boulevard Lionel-Boulet, Varennes, Qc Canada J3X1S2
| | - My Ali El Khakani
- Institut National de la Recherche Scientifique, Centre Énergie Matériaux et Télécommunications, 1650 Boulevard Lionel-Boulet, Varennes, Qc Canada J3X1S2
| | - François Légaré
- Institut National de la Recherche Scientifique, Centre Énergie Matériaux et Télécommunications, 1650 Boulevard Lionel-Boulet, Varennes, Qc Canada J3X1S2
| |
Collapse
|
107
|
Wanapun D, Kestur US, Kissick DJ, Simpson GJ, Taylor LS. Selective Detection and Quantitation of Organic Molecule Crystallization by Second Harmonic Generation Microscopy. Anal Chem 2010; 82:5425-32. [PMID: 20515064 DOI: 10.1021/ac100564f] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Duangporn Wanapun
- Departments of Chemistry and Industrial and Physical Pharmacy, Purdue University, West Lafayette, Indiana 47907
| | - Umesh S. Kestur
- Departments of Chemistry and Industrial and Physical Pharmacy, Purdue University, West Lafayette, Indiana 47907
| | - David J. Kissick
- Departments of Chemistry and Industrial and Physical Pharmacy, Purdue University, West Lafayette, Indiana 47907
| | - Garth J. Simpson
- Departments of Chemistry and Industrial and Physical Pharmacy, Purdue University, West Lafayette, Indiana 47907
| | - Lynne S. Taylor
- Departments of Chemistry and Industrial and Physical Pharmacy, Purdue University, West Lafayette, Indiana 47907
| |
Collapse
|
108
|
Nadiarnykh O, LaComb RB, Brewer MA, Campagnola PJ. Alterations of the extracellular matrix in ovarian cancer studied by Second Harmonic Generation imaging microscopy. BMC Cancer 2010; 10:94. [PMID: 20222963 PMCID: PMC2841668 DOI: 10.1186/1471-2407-10-94] [Citation(s) in RCA: 176] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2009] [Accepted: 03/11/2010] [Indexed: 11/13/2022] Open
Abstract
Background Remodeling of the extracellular matrix (ECM) has been implicated in ovarian cancer, and we hypothesize that these alterations may provide a better optical marker of early disease than currently available imaging/screening methods and that understanding their physical manifestations will provide insight into invasion. Methods For this investigation we use Second Harmonic Generation (SHG) imaging microcopy to study changes in the structure of the ovarian ECM in human normal and malignant ex vivo biopsies. This method directly visualizes the type I collagen in the ECM and provides quantitative metrics of the fibrillar assembly. To quantify these changes in collagen morphology we utilized an integrated approach combining 3D SHG imaging measurements and bulk optical parameter measurements in conjunction with Monte Carlo simulations of the experimental data to extract tissue structural properties. Results We find the SHG emission attributes (directionality and relative intensity) and bulk optical parameters, both of which are related to the tissue structure, are significantly different in the tumors in a manner that is consistent with the change in collagen assembly. The normal and malignant tissues have highly different collagen fiber assemblies, where collectively, our findings show that the malignant ovaries are characterized by lower cell density, denser collagen, as well as higher regularity at both the fibril and fiber levels. This further suggests that the assembly in cancer may be comprised of newly synthesized collagen as opposed to modification of existing collagen. Conclusions Due to the large structural changes in tissue assembly and the SHG sensitivity to these collagen alterations, quantitative discrimination is achieved using small patient data sets. Ultimately these measurements may be developed as intrinsic biomarkers for use in clinical applications.
Collapse
Affiliation(s)
- Oleg Nadiarnykh
- Center for Cell Analysis and Modeling, Department of Cell Biology, University of Connecticut Health Center, Farmington, CT 06030, USA
| | | | | | | |
Collapse
|
109
|
Akins ML, Luby-Phelps K, Mahendroo M. Second harmonic generation imaging as a potential tool for staging pregnancy and predicting preterm birth. JOURNAL OF BIOMEDICAL OPTICS 2010; 15:026020. [PMID: 20459265 PMCID: PMC2874049 DOI: 10.1117/1.3381184] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
We use second harmonic generation (SHG) microscopy to assess changes in collagen structure of murine cervix during cervical remodeling of normal pregnancy and in a preterm birth model. Visual inspection of SHG images revealed substantial changes in collagen morphology throughout normal gestation. SHG images collected in both the forward and backward directions were analyzed quantitatively for changes in overall mean intensity, forward to backward intensity ratio, collagen fiber size, and porosity. Changes in mean SHG intensity and intensity ratio take place in early pregnancy, suggesting that submicroscopic changes in collagen fibril size and arrangement occur before macroscopic changes become evident. Fiber size progressively increased from early to late pregnancy, while pores between collagen fibers became larger and farther apart. Analysis of collagen features in premature cervical remodeling show that changes in collagen structure are dissimilar from normal remodeling. The ability to quantify multiple morphological features of collagen that characterize normal cervical remodeling and distinguish abnormal remodeling in preterm birth models supports future studies aimed at development of SHG endoscopic devices for clinical assessment of collagen changes during pregnancy in women and for predicting risk of preterm labor which occurs in 12.5% of all pregnancies.
Collapse
Affiliation(s)
- Meredith L Akins
- University of Texas Southwestern Medical Center, Department of Obstetrics and Gynecology, 5323 Harry Hines Boulevard, Dallas, Texas 75390, USA
| | | | | |
Collapse
|
110
|
Zimmerley M, McClure RA, Choi B, Potma EO. Following dimethyl sulfoxide skin optical clearing dynamics with quantitative nonlinear multimodal microscopy. APPLIED OPTICS 2009; 48:D79-87. [PMID: 19340127 PMCID: PMC2803712 DOI: 10.1364/ao.48.000d79] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Second-harmonic generation (SHG) imaging is combined with coherent anti-Stokes Raman scattering (CARS) microscopy to follow the process of optical clearing in human skin ex vivo using dimethyl sulfoxide (DMSO) as the optical clearing agent. SHG imaging revealed that DMSO introduces morphological changes to the collagen I matrix. By carefully measuring the dynamic tissue attenuation of the coherent nonlinear signal, using CARS reference signals during the clearing process, it is found that DMSO reduces the overall SHG response from dermal collagen. Evidence is provided for a role of DMSO in compromising the structure of collagen fibers, associated with a reduction of the tissue's scattering properties.
Collapse
Affiliation(s)
- Maxwell Zimmerley
- Department of Chemistry, University of California, Irvine, California 92697, USA
| | - R. Anthony McClure
- Department of Neurobiology, University of California, Irvine, California 92697, USA
| | - Bernard Choi
- Department of Biomedical Engineering, University of California, California 92697, USA
- Beckman Laser Institute, University of California, Irvine, California 92697, USA
| | - Eric Olaf Potma
- Department of Chemistry, University of California, Irvine, California 92697, USA
- Beckman Laser Institute, University of California, Irvine, California 92697, USA
- Corresponding author:
| |
Collapse
|
111
|
Nadiarnykh O, Campagnola PJ. Retention of polarization signatures in SHG microscopy of scattering tissues through optical clearing. OPTICS EXPRESS 2009; 17:5794-806. [PMID: 19333348 PMCID: PMC4487673 DOI: 10.1364/oe.17.005794] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Polarization responses in Second Harmonic Generation (SHG) imaging microscopy are a valuable method to quantify aspects of tissue structure, and may be a means to differentiate normal and diseased tissues. Due to multiple scattering, the polarization data is lost in turbid tissues. Here we investigate if this information can be retained through the use of optical clearing which greatly reduces the scattering coefficient and increases the corresponding mean free path. To this end, we have measured the SHG intensity as a function of laser polarization and the SHG signal anisotropy in murine tendon and striated muscle over a depth range of 200 microns. We find that the laser polarization is highly randomized in the uncleared tissues at depths corresponding to only 2-3 scattering collisions (50- 10 microns). This depolarization of the laser is also reflected in the randomized anisotropy of the SHG signal as it is created over a range of polarization states. In strong contrast, both polarization signatures are significantly retained through ~200 microns of tissue thickness following treatment with 50% glycerol. Moreover, the measured polarization responses for both tendon and striated muscle are consistent with the extent of reduction of the respective scattering coefficients upon clearing. We suggest the method will be applicable to SHG imaging of connective disorders as well as cancer through several hundred microns of extracellular matrix.
Collapse
|
112
|
Changes in the biochemical constituents and morphologic appearance of the human cervical stroma during pregnancy. Eur J Obstet Gynecol Reprod Biol 2009; 144 Suppl 1:S82-9. [PMID: 19303693 DOI: 10.1016/j.ejogrb.2009.02.008] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE The cervix is the lower portion of the uterus. It is composed of fibrous tissue and its mechanical integrity is crucial for maintaining a healthy gestation. During normal pregnancy, the cervical extracellular matrix (ECM) remodels in preparation for labor. The objective of this study was to investigate the biochemical and morphological changes in cervical stroma associated with physiological remodeling during normal pregnancy. STUDY DESIGN Using human cervical tissue obtained from pregnant and non-pregnant patients, the ECM was analyzed for its biochemical constituents and histologic morphology. The ECM was assayed for hydration, collagen concentration, collagen solubility, total sulfated glycosaminoglycan concentration, and individual disaccharide concentration. The ECM morphology was visualized using conventional histological techniques (Masson's trichrome stain, polarized light microscopy) as well as second harmonic generation (SHG) imaging. RESULTS When comparing pregnant to non-pregnant tissue, significant increases were measured for total sulfated glycosaminoglycans, hyaluronic acid, and collagen solubility. The microscopy studies confirmed that the collagenous network of the cervical stroma was anisotropic and pregnancy was associated with a discernable decrease in collagen organization. CONCLUSION Significant changes were seen in the concentration and organization of cervical ECM constituents during normal pregnancy.
Collapse
|
113
|
LaComb R, Nadiarnykh O, Carey S, Campagnola PJ. Quantitative second harmonic generation imaging and modeling of the optical clearing mechanism in striated muscle and tendon. JOURNAL OF BIOMEDICAL OPTICS 2008; 13:021109. [PMID: 18465958 DOI: 10.1117/1.2907207] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
We have investigated the mechanisms and capabilities of optical clearing in conjunction with second harmonic generation (SHG) imaging in tendon and striated muscle. Our approach combines three-dimensional (3-D) SHG imaging of the axial attenuation and directional response with Monte Carlo simulation (based on measured bulk optical properties) of the creation intensity and propagation through the tissues. Through these experiments and simulations, we show that reduction of the primary filter following glycerol treatment dominates the axial attenuation response in both muscle and tendon. However, these disparate tissue types are shown to clear through different mechanisms of the glycerol-tissue interaction. In the acellular tendon, glycerol application reduces scattering by both index matching as well as increasing the interfibril separation. This results in an overall enhancement of the 3-D SHG intensity, where good agreement is found between experiment and simulation. Through analysis of the axial response as a function of glycerol concentration in striated muscle, we conclude that the mechanism in this tissue arises from matching of the refractive index of the cytoplasm of the muscle cells with that of the surrounding higher-index collagenous perimysium. We further show that the proportional decrease in the scattering coefficient mu(s) with increasing glycerol fraction can be well-approximated by Mie theory.
Collapse
Affiliation(s)
- Ronald LaComb
- University of Connecticut Health Center, Department of Cell Biology, Center for Cell Analysis and Modeling, Farmington, Connecticut 06030, USA
| | | | | | | |
Collapse
|
114
|
Quantitative second harmonic generation imaging of the diseased state osteogenesis imperfecta: experiment and simulation. Biophys J 2008; 94:4504-14. [PMID: 18281387 DOI: 10.1529/biophysj.107.114405] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We report the integrated use of 3D second harmonic generation (SHG) imaging microscopy and Monte Carlo simulation as a combined metric to quantifiably differentiate normal and diseased tissues based on the physical properties of the respective extracellular matrix. To achieve this, we have identified a set of parameters comprised of the SHG creation attributes and the bulk optical parameters, which are used collectively via comparative analysis. Monte Carlo simulations of the SHG axial directional and attenuation responses allow their decomposition into the underlying factors that are not readily obtainable through experimental techniques. Specifically, this approach allows for estimation of the SHG creation attributes (directionality and relative conversion efficiency) and separation of primary and secondary filter effects, collectively that form the observed SHG contrast. The quantitative metric is shown for the connective tissue disorder Osteogenesis Imperfecta (characterized by abnormal assembly of type I collagen) using a murine model that expresses the disease in the dermis layer of skin. Structural dissimilarities between the osteogenesis imperfecta mouse and wild-type tissues lead to significant differences in the SHG depth-dependent directionality and signal attenuation. The Monte Carlo simulations of these responses using measured bulk optical parameters reproduce the experimental data trends, and the extracted emission directionality and conversion efficiencies are consistent with independent determinations. The simulations also illustrate the dominance of primary filter affects on overall SHG generation and attenuation. Thus, the combined method of 3D SHG imaging and modeling forms an essential foundation for parametric description of the matrix properties that are not distinguishable by sole consideration of either bulk optical parameters or SHG alone. Moreover, due to the quasi-coherence of the SHG process in tissues, we submit that this approach contains unique information not possible by purely scattering based methods and that these methods will be applicable in the general case where the complex fibrillar structure is difficult to fully quantify via morphological analysis.
Collapse
|