Brillouin Scattering Microscopy for Mechanical Imaging
File(s)
Author(s)
Antonacci, Giuseppe
Type
Thesis
Abstract
In a world where science is constantly challenged to solve problems of increasing
complexity, light is paving new ways to gather information about the physical
properties of matter. Among these properties, elasticity is becoming fundamental in
the understanding and the diagnosis of several diseases. Current solutions to gather
mechanical information, however, measure the response of a material to an applied
excitation, which makes them invasive and limited by a low spatial resolution. In
contrast with these techniques, Brillouin spectroscopy offers the unique solution to
retrieve stiffness information from the spectrum of the light scattered by inherent
thermal acoustic waves.
The combination of Brillouin spectroscopy with confocal microscopy has yielded
a confocal Brillouin microscope able to perform mechanical imaging in a non-invasive
manner. This was used to investigate two different biological problems: on the
one hand the stiffness variations in specific endothelium cells of the eye, aiming
at a better understanding of the mechanisms responsible for glaucoma, and on the
other the characterisation of the mechanical structures of blood vessels, which could
provide fundamental information regarding the formation of atherosclerotic plaques.
Following an investigation on the optimal geometry that minimises the spectral
broadening caused by the collection of photons over a range of scattering angles, high
resolution Brillouin imaging was obtained in a confocal backscattering arrangement.
To the best of our knowledge this thesis presents, for the first time, sub-cellular
Brillouin images. In particular, in vitro Brillouin images of single HUVEC cells
were acquired to investigate the cell’s mechanical response to the application of the
Latrunculin-A drug. This analysis, together with the finding of a linear correlation
between the Brillouin modulus and the standard Young’s modulus, validates the
technique as a feasible means of measuring stiffness. Following this assessment,
Brillouin images of normal and diseased vessels were acquired showing that the
atherosclerotic plaques had a lower stiffness compared to both diseased and healthy
vessel walls. These results might encourage the application of confocal Brillouin
microscopy as the tool of choice for the investigation of the arterial biomechanics.
complexity, light is paving new ways to gather information about the physical
properties of matter. Among these properties, elasticity is becoming fundamental in
the understanding and the diagnosis of several diseases. Current solutions to gather
mechanical information, however, measure the response of a material to an applied
excitation, which makes them invasive and limited by a low spatial resolution. In
contrast with these techniques, Brillouin spectroscopy offers the unique solution to
retrieve stiffness information from the spectrum of the light scattered by inherent
thermal acoustic waves.
The combination of Brillouin spectroscopy with confocal microscopy has yielded
a confocal Brillouin microscope able to perform mechanical imaging in a non-invasive
manner. This was used to investigate two different biological problems: on the
one hand the stiffness variations in specific endothelium cells of the eye, aiming
at a better understanding of the mechanisms responsible for glaucoma, and on the
other the characterisation of the mechanical structures of blood vessels, which could
provide fundamental information regarding the formation of atherosclerotic plaques.
Following an investigation on the optimal geometry that minimises the spectral
broadening caused by the collection of photons over a range of scattering angles, high
resolution Brillouin imaging was obtained in a confocal backscattering arrangement.
To the best of our knowledge this thesis presents, for the first time, sub-cellular
Brillouin images. In particular, in vitro Brillouin images of single HUVEC cells
were acquired to investigate the cell’s mechanical response to the application of the
Latrunculin-A drug. This analysis, together with the finding of a linear correlation
between the Brillouin modulus and the standard Young’s modulus, validates the
technique as a feasible means of measuring stiffness. Following this assessment,
Brillouin images of normal and diseased vessels were acquired showing that the
atherosclerotic plaques had a lower stiffness compared to both diseased and healthy
vessel walls. These results might encourage the application of confocal Brillouin
microscopy as the tool of choice for the investigation of the arterial biomechanics.
Version
Open Access
Date Issued
2015-02
Date Awarded
2015-05
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Török, Peter
Paterson, Carl
Sponsor
Engineering and Physical Sciences Research Council
Grant Number
PHPT PSA340
Publisher Department
Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)