Biomedical Engineering Reference
In-Depth Information
13
Multiphoton Excitation
Imaging of the Arterial
Vascular Bed
13.1 Introduction ......................................................................................289
13.2 Methodology and Preparations ......................................................290
Nonlinear Optical Applications in the Vessel Wall
13.3 Arterial Sample Preparations .........................................................294
In Vitro • In Vivo
13.4 Investigation of Macromolecular Structure .................................296
Elastin
•
Collagen
•
Macromolecular Exogenous Probes
13.5 Investigations of Vessel Mechanics................................................298
Residual Strain
•
Deformation
13.6 Investigations of LDL Interactions with
the Vascular Wall..............................................................................299
13.7 Investigations of the Diseased Vascular Wall ..............................301
Atherosclerosis
•
Other Diseases
13.8 Summary and Future Directions ...................................................304
References......................................................................................................305
Edward B. Neufeld
National Institutes of
Health
Bertrand M. Lucotte
National Institutes of
Health
Robert S. Balaban
National Institutes of
Health
13.1 introduction
Multiphoton excitation microscopy provides a powerful means to study the macromolecular micro-
structure of the arterial vascular bed. The multiphoton effect restricts excited light to the focal spot,
allowing optical sectioning without the need for a confocal pinhole. This provides greatly improved
photon collection efficiency (compared with single-photon confocal imaging), while maintaining three-
dimensional submicrometric spatial resolution. Moreover, owing to the reduced tissue scattering of
near-infrared excitation beams, deeper tissue penetration with minimal tissue damage can be attained.
hough second- and higher-order harmonic generation (HG) is the major focus of this topic, other
nonlinear optical contrast mechanisms are simultaneously generated such as multiphoton excitation
fluorescence (MEF), and with a second excitation laser, coherent anti-Stokes Raman scattering (CARS).
These nonlinear optical microscopy techniques can be used to record three-dimensional, fully regis-
tered images of the major macromolecular elements of the arterial wall without stains or dyes. These
three readout mechanisms, together with appropriate exogenous probes, can provide a wealth of infor-
mation concerning the three major elements of the diseased vascular wall, collagen (HG), elastin (MEF),
and fat (CARS). These imaging technologies provide
en face
imaging of wall structures relative to the
blood, allowing for improved evaluation of interactions of wall structures with the vascular space, and,
in specialized cases, can provide information
in vivo
.
289