title: Polarization second harmonic generation microscopy provides quantitative enhanced molecular specificity for tissue diagnostics.
abstract: Due to specific structural organization at the molecular level, several biomolecules (e.g., collagen, myosin etc.) which are strong generators of second harmonic generation (SHG) signals, exhibit unique responses depending on the polarization of the excitation light. By using the polarization second harmonic generation (p-SHG) technique, the values of the second order susceptibility components can be used to differentiate the types of molecule, which cannot be done by the use of a standard SHG intensity image. In this report we discuss how to implement p-SHG on a commercial multiphoton microscope and overcome potential artifacts in susceptibility (χ) image. Furthermore we explore the potential of p-SHG microscopy by applying the technique to different types of tissue in order to determine corresponding reference values of the ratio of second-order χ tensor elements. These values may be used as a bio-marker to detect any structural alterations in pathological tissue for diagnostic purposes. The SHG intensity image (red) in (a) shows the distribution of collagen fibers in ovary tissue but cannot determine the type of collagen fiber. However, the histogram distribution (b) for the values of the χ tensor element ratio can be used to quantitatively identify the types of collagen fibers.
authors.affiliation: Department of Physics, Norwegian University of Science and Technology (NTNU), N-7491, Trondheim, Norway. rajesh.kumar@ntnu.no, 101rajesh@gmail.com.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Kumar
authors.affiliation: Levanger Hospital, Norway.
authors.forename: Kirsten M
authors.initials: KM
authors.lastname: Grønhaug
authors.affiliation: Department of Physics, Norwegian University of Science and Technology (NTNU), N-7491, Trondheim, Norway.
authors.forename: Elisabeth I
authors.initials: EI
authors.lastname: Romijn
authors.affiliation: Department of Physics, Norwegian University of Science and Technology (NTNU), N-7491, Trondheim, Norway.
authors.forename: Andreas
authors.initials: A
authors.lastname: Finnøy
authors.affiliation: Department of Physics, Norwegian University of Science and Technology (NTNU), N-7491, Trondheim, Norway.
authors.forename: Catharina L
authors.initials: CL
authors.lastname: Davies
authors.affiliation: Trondheim University Hospital, Norway.
authors.forename: Jon O
authors.initials: JO
authors.lastname: Drogset
authors.affiliation: Department of Physics, Norwegian University of Science and Technology (NTNU), N-7491, Trondheim, Norway.
authors.forename: Magnus B
authors.initials: MB
authors.lastname: Lilledahl
mesh_terms: D016477:Artifacts; D002356:Cartilage / Q000473:pathology; D019937:Diagnostic Techniques and Procedures; D005260:Female; D006801:Humans; D008859:Microscopy, Polarization / Q000379:methods*; D009206:Myocardium / Q000166:cytology; D010003:Osteoarthritis / Q000473:pathology; D010053:Ovary / Q000166:cytology
keywords: biomedical optical diagnosis; collagen fiber; human knee articular cartilage; multiphoton microscopy; nonlinear optical imaging; osteoarthritis; polarization second harmonic generation (p-SHG) microscopy; susceptibility (χ) tensor imaging