Biomedical Engineering Reference
In-Depth Information
a 12-fs Ti:sapphire laser with a wavelength of 800 nm and a spectral bandwidth
of 100 nm to provide short pulses necessary for efficient multiphoton excitation
and the wide bandwidth for high-resolution OCT [ 26 ]. Vinegoni et al. combined
optical coherence microscopy (OCM), MPM, and second harmonic generation
(SHG) microscopy using a frequency-doubled Nd:YVO4-pumped Ti:sapphire laser
with a center wavelength of 800 nm, a bandwidth of 60 nm, and an 80-MHz pulse
repetition rate [ 27 ]. It was demonstrated that this system allows for the simultaneous
acquisition of both anatomical (structural) and functional imaging information for
applications in the fields of tissue engineering and cell biology.
9.2.6
System Combining Optical and X-Ray Imaging
Techniques
Animal models are commonly used to study morphological changes of the diseased
tissues in traditional research on disease mechanisms. This requires the excision
and pathological study of the tissue of interest. Usually, it takes a long time period
for measurable changes to occur and requires a large number of animal subjects
because a number of animals are often sacrificed at each time point for histological
evaluation.
Optical molecular imaging has been developed to study the disease process
at the molecular level within living animals using fluorescence imaging contrast
agents. This method has the potential in detecting specific molecular and metabolic
changes within target tissues long before morphological changes can be detected.
One advantage of fluorescence optical imaging is that the molecular changes can
be monitored in vivo without sacrificing the animal. It has been routinely used in
preclinical research and drug development.
While optical molecular imaging provides good sensitivity and specificity to
molecular targets, it does not provide the appropriate contextual anatomical data
for accurate localization of the molecular imaging signals within the animal. On the
other hand, as a nonoptical imaging technique, X-ray imaging can provide accurate
anatomical information and even 3-D anatomical information through computed
tomography (CT).
Combining optical molecular imaging with X-ray imaging can provide both
anatomical and functional information, with X-ray images providing the detailed
penetrating anatomical guideposts to enhance the localization of the optical molec-
ular imaging agent [ 28 ]. This approach can enhance the localization of molecular
signals in live animals, with the anatomical information from X-ray imaging and
the molecular signals from optical imaging. X-ray images are typically overlaid
with optical images, allowing functional quantitative fluorescence data to be
spatially/anatomically defined against the skeletal structure.
To combine an optical molecular imaging system and an X-ray imaging system,
usually one high-sensitivity cooled CCD camera is needed to take both the
fluorescence image and X-ray image through the scintillator plate, as shown in
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