Used with permission. To achieve high-resolution confocal imaging, exogenous fluorescence agents were applied. By using these exogenous fluorescence techniques, confocal images were acquired simultaneously with endoscopic images, making it possible to identify typical histological structures in the human gastrointestinal tract, shown in Figure 2 [ 20 ]. This confocal microendoscope was further applied to detect cellular and vascular changes and distinguish different types of epithelial cell [ 30 ].
Upper row: optical possibilities of confocal endomicroscopy. A Normal endoscopic view. B High-resolution or magnifying endoscopy image. C Confocal endomicroscopy image. Lower row: normal crypt architecture. D Confocal endomicroscopy with fluorescein intravenously given. E Conventional histology in horizontal sectioning of normal crypt architecture. F Confocal endomicroscopy after topical application of acriflavine.
Wide-field fluorescence imaging allows rapid visualization of large surface areas in hollow organs, leading to disease localization and optical biopsy guidance [ 12 ]. With the advances in miniaturization of video charge-coupled device CCD chip, wide-field fluorescence imaging by microendoscope is involving rapidly [ 31 ].
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By scanning a SMF in a spiral pattern through a tubular piezoelectric actuator, a scanning fiber endoscopy SFE was proposed to create an image with a large field of view FOV and high resolution [ 21 , 32 ]. The distal tip had an outer diameter of 3. C White light endoscopic system image under reflectance mode.
D Reflectance and laser-induced green fluorescence. E Reflectance and laser-induced blue fluorescence. This technique was initially proposed to detect fluorescence to visualize overexpressed molecular targets [ 33 ].
Recently, it was demonstrated as a multimodal laser-based angioscopy which is potentially a powerful platform for research, diagnosis, prognosis, and image-guided local therapy in atherosclerosis and cardiovascular disease [ 21 ]. The small size of the SFE allowed for collecting high-resolution images from the esophagus, stomach, and colon in the mouse models to perform in-depth imaging for study of molecular mechanisms of disease [ 34 , 35 ]. The compact probe design based on spiral scanning of fiber instrument enabled a miniature package compatible with standard medical endoscopes.
Multiphoton fluorescence and second-harmonic generation SHG are nonlinear imaging techniques for noninvasive, high-resolution, real-time diagnostics of tissues at subcellular resolution. They are based on exciting and detecting nonlinear optical signals from biological tissues [ 13 , 14 , 15 ]. Consequently, depth-resolved imaging is enabled because the excitation of nonlinear signals happens only within the focal volume of the laser beam. It is a functional imaging technique in which the contrasts from nicotinamide adenine dinucleotide hydrogen NADH , flavin adenine dinucleotide FAD , elastin, and collagen are biochemically specific.
Therefore, they allow label-free imaging without any exogenous contrast agent. Currently, multiphoton fluorescence and SHG microscopy have mainly been carried out on a microscope stage on the laboratory bench [ 13 , 14 , 15 ]. They achieved imaging at approximately a speed of 4. GRIN lens has a small diameter and cylindrical geometry. System components and setup. A Mechanical assembly of the microendoscope. B Photograph of the prototype. C Imaging setup. Ex vivo images of mouse tissue was acquired as shown in Figure 5 [ 37 ].
In tissue, SHG contrast mainly comes from collagen, and thus it is especially useful for imaging cartilage, bone, tendon, the skin, and cornea where collagen is the most abundant extracellular matrix protein in the tissues [ 39 ]. The intrinsic TPEF signal can be observed from cells, collagen, and elastin fibers.
The rigid probe based on a GRIN lens is more desirable in laparoscopic applications or in interfacing with a biopsy probe. Currently, the Xingde Li group developed a handheld rigid probe with multiphoton fluorescence and SHG techniques for optical biopsy Figure 6A—C [ 22 ]. The probe could fit within a gauge biopsy needle.
A SMF was used for delivery of femtosecond pulses, and a multimode fiber MMF with a large core diameter was used at the proximal end of the rigid probe to deliver the signal to a detector. Handheld rigid probe and TPEF images.
A Handheld probe design schematic. B Photo of the handheld rigid probe. C Photo of the rigid probe inside a gauge biopsy needle. Photoacoustic tomography PAT is a relatively new technique that overcomes the limitations of existing pure optical imaging by detecting optical absorption contrast via the photoacoustic PA effect [ 16 ].
In PAT, a laser excites photoacoustic waves generated by rapid thermoelastic expansion through optical absorption of short laser pulse PA effect , and ultrasound transducers detect the photoacoustic waves [ 40 ]. Additionally, PAT allows label-free imaging with endogenous contrast. Thus, the PAT technique has been evolving rapidly with applications in various biological processes over the past decade. A rotating mirror acting as a scanner reflected the ultrasonic waves and laser pulses, and it was statically mounted with the associated illumination and ultrasonic pulse-generation detection units.
The reflected ultrasonic and photoacoustic waves were detected and converted into electric signals via the ultrasonic transducer to a computer. By inserting the side-scanning 3. However, only photoacoustic images showed their adjacent vasculatures. These experimental results demonstrated the deep imaging ability of the dual-mode microendoscope and the complementary contrast production.
Illustration of simultaneous, multiwavelength PA and ultrasonic endoscopy. A The endoscope design. B A photo shows the side-scanning 3. C Definition of Cartesian and cylindrical coordinate systems. D A volumetric image. E A representative cross section of d along the x-y plane. F Three-dimensionally rendered PA structural image.
A review of imaging techniques for systems biology | BMC Systems Biology | Full Text
G Co-registered US structural image for the same volume of F. H An overlaid image of F and G. J Corresponding US cross-sectional image of I. K A combined image of I and J. Surface-enhanced Raman scattering SERS is a plasmonic effect resulting enhanced Raman signals from molecules which have been attached to nanometer-sized metallic structures [ 17 , 18 , 19 ]. SERS nanoparticle-based Raman spectroscopy is a spectrally molecular imaging technique allowing for ultrahigh sensitivity and the unique ability to multiplex readouts from a variety of molecular targets using a single wavelength of excitation [ 42 ].
In the Raman imaging system, the gold-based nanoparticles S, S, S, and S as shown in Figure 8 can dramatically increase the Raman scattered light emitted by small molecules adsorbed onto the surface [ 45 , 46 ]. The advantage of multiplexing is that it simultaneously detects multiple biomarkers if each type of nanoparticles binds to a different protein target. Consequently, verity types of conjugated SERS nanoparticles with the tumor-targeting capabilities in preclinical animal models have been investigated [ 47 , 48 , 49 , 50 ].
click A Gold nanoparticles are covered with a layer of Raman active material and then a silica coating. The background spectrum is acquired in the same experimental arrangement without nanoparticles. Students, technicians, and researchers will find it useful whether they are intending to use the techniques, have been using the techniques for some time, or are merely curious to know more about what the techniques can offer the cell biologist. We provide complimentary e-inspection copies of primary textbooks to instructors considering our books for course adoption.
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Stay on CRCPress. Preview this Book. Add to Wish List. Close Preview. Toggle navigation Additional Book Information. Summary Optical Imaging Techniques in Cell Biology, Second Edition covers the field of biological microscopy, from the optics of the microscope to the latest advances in imaging below the traditional resolution limit.