The authors report on the feasibility of clinical neuroendovascular optical coherence tomography (OCT)
imaging as well as its efficacy and safety by comparing findings with histology in animal, cadaveric and
clinical studies. Catheter-based in vivo endovascular OCT imaging was carried out intracranially in four
patients, three in the anterior circulation and one in the posterior circulation (vertebral artery). The
neuroendovascular OCT device was delivered to the desired location using groin access and standard
endovascular procedures. In vivo findings were reproduced using ex vivo OCT imaging in corresponding
animal and human (cadaveric) harvested tissue segments with findings matched by histology. OCT images
correlated well with the images obtained after histologic sectioning, and visualized in vivo the laminar
vascular structure. Satisfactory imaging findings were obtained with no complications. Neuroendovascular
OCT imaging is thus feasible for clinical use and can detect with high resolution the structure of arterial
segments. Understanding OCT imaging in non-diseased arteries is important in establishing baseline
findings necessary for interpreting pathologic processes. This allows neuroendovascular optical biopsies of
vascular tissue to be obtained without the need for excision and processing, and potentially allows
prophylactic interventions against stroke and other cerebrovascular disease before they become
symptomatic.
Optical coherence tomography (OCT) is a noninvasive, high-resolution imaging technology capable of delivering real-time, near-histologic images of tissues. Mustard gas is a vesicant-blistering agent that can cause severe and lethal damage to airway and lungs. The ability to detect and assess airway injury in the clinical setting of mustard exposure is currently limited. The purpose of this study is to assess the ability to detect and monitor progression of half-mustard [2-chloroethylethylsulfide (CEES)] airway injuries with OCT techniques. A ventilated rabbit mustard exposure airway injury model is developed. A flexible fiber optic OCT probe is introduced into the distal trachea to image airway epithelium and mucosa in vivo. Progression of airway injury is observed over eight hours with OCT using a prototype time-domain superluminescent diode OCT system. OCT tracheal images from CEES exposed animals are compared to control rabbits for airway mucosal thickening and other changes. OCT detects the early occurrence and progression of dramatic changes in the experimental group after exposure to CEES. Histology and immunofluorescence staining confirms this finding. OCT has the potential to be a high resolution imaging modality capable of detecting, assessing, and monitoring treatment for airway injury following mustard vesicant agent exposures.
Optical coherence tomography (OCT) is a catheter-based imaging technology with powerful resolution capable of identifying vulnerable plaques and guiding coronary intervention. However, a significant limitation of intravascular OCT imaging is its attenuation by blood. We propose that the use of an oxygen-carrying blood substitute could potentially optimize OCT image quality. Surgical isolation of the descending thoracic aorta of six rabbits is performed, followed by intravascular OCT imaging of the abdominal aorta. Perfluorodecalin (PFD) is oxygenated using a bubble-through technique with 100% oxygen. OCT imaging is performed and compared using three different flushing modalities: PFD; saline; and blood. OCT imaging of the rabbit abdominal aorta is successful in all of the subjects. In each of the six studied subjects, flushing with PFD consistently provides dramatically better imaging of the vessel wall tissue structures. OCT image quality is highly dependent on the ability of the flushing modality to remove blood from the imaging field. From this proof-of-concept study, we demonstrate that endovascular flushing with an oxygen-carrying blood substitute (PFD) is optically superior to saline flushing for intravascular imaging.
A multiphoton endoscopy system has been developed using a two-axis microelectromechanical systems (MEMS) mirror and double-cladding photonic crystal fiber (DCPCF). The MEMS mirror has a 2-mm-diam, 20-deg optical scanning angle, and 1.26-kHz and 780-Hz resonance frequencies on the x and y axes. The maximum number of resolvable focal spots of the MEMS scanner is 720×720 on the x and y axes, which indicates that the MEMS scanner can potentially support high-resolution multiphoton imaging. The DCPCF is compared with standard single-mode fiber and hollow-core photonic bandgap fiber on the basis of dispersion, attenuation, and coupling efficiency properties. The DCPCF has high collection efficiency, and its dispersion can be compensated by grating pairs. Three configurations of probe design are investigated, and their imaging quality and field of view are compared. A two-lens configuration with a collimation and a focusing lens provides the optimum imaging performance and packaging flexibility. The endoscope is applied to image fluorescent microspheres and bovine knee joint cartilage.
We present a kind of rotational two photon mciroendoscopy for 1μm fiber
femtosecond laser. The fiber laser provide ultrashort femto-second pulses with center
wavelength at 1.034μm and repetition rate of 50MH. The rotational probe is based on
double cladding photonic crystal fiber (CD PCF) fiber, Grin lens, microprism and
rotational MEMS motor. The MEMS motor has diameter of 2.2mm and can provide
360 degree full view rotation. We experimentally show that the DC PCF fiber works
for 1μm fiber laser two photon system. Second harmonic generation (SHG) singnal
line profile of rat tail tendon and fish scale was taken with the endoscopy system.
Optical coherence tomography (OCT) is an evolving noninvasive imaging modality that has been used to image the human larynx during surgical endoscopy. The design of a long gradient-index lens-based probe capable of capturing images of the human larynx by use of spectral domain OCT during a typical office-based laryngoscopy examination is presented. An optical-ballast-based 4f optical relay system is proposed to realize variable working distance with a constant optical delay. In-vivo OCT imaging of the human larynx is demonstrated. Office-based OCT is a promising imaging modality for early laryngeal cancer diagnosis.
KEYWORDS: Digital signal processing, Optical coherence tomography, Endoscopes, Signal processing, Microelectromechanical systems, 3D image processing, Image processing, Coherence imaging, 3D acquisition, Signal detection
A fast-scan-rate swept laser for optical coherence tomography (OCT) is suitable to record and analyze a 3-D image volume. However, the whole OCT system speed is limited by data streaming, processing, and storage. In this case, postprocessing is a common technique. Endoscopic clinical applications prefer onsite diagnosis, which requires a real-time technique. Parallel digital signal processors were applied to stream and process data directly from a data digitizer. A real-time system with 20-kHz axial line speed, which was limited only by our swept laser scan rate, was implemented. To couple with the system speed, an endoscope based on an improved 3-D microelectromechanical motor (diameter 1.5 mm, length 9.4 mm) was developed. In vivo 3-D imaging of the human airway was demonstrated.
Smoke inhalation injury causes acute airway injury that may result in airway compromise with significant morbidity and mortality. We investigate the ability of high resolution endobronchial optical coherence tomography (OCT) to obtain real-time images for quantitatively assessing regional differences between upper tracheal versus lower tracheal and bronchial airway injury responses to smoke inhalation in vivo using a prototype spectral domain (SLD)-OCT system we constructed, and flexible fiber optic probes. 33 New Zealand White rabbits are intubated and mechanically ventilated. The treatment groups are exposed to inhaled smoke. The OCT probe is introduced through the endotracheal tube and maintained in place for 5 to 6 h. Images of airway mucosa and submucosa are obtained at baseline and at specified intervals postexposure. Starting within less than 15 min after smoke inhalation, there is significant airway thickening in the smoke-exposed animals. This is maintained over 5 h of imaging studies. The lower tracheal airway changes, correlating closely with carboxyhemoglobin levels, are much greater than upper tracheal changes. Significant differences are seen in lower trachea and bronchi after acute smoke inhalation compared to upper trachea as measured in vivo by minimally invasive OCT. OCT is capable of quantitatively detecting regional changes in airway swelling following inhalation injury.
Angiography is currently used to assess post-treatment human brain aneurysm
healing, which can reveal vessel shape only. Optical coherence tomography (OCT) can reveal
the vessel wall structure with high resolution, which has the advantage to assess vessel healing
progress. An OCT endovascular catheter was designed and in vivo patients' studies were
performed. Flush effect of saline and perfluorodecalin (PFC) were studies in rabbit aorta. The
initial results show that OCT is a promising technology to assess post-treatment cerebrovascular
diseases.
In vivo three dimensional endoscopic imaging of rabbit and human gastrointestinal tracts was demonstrated based on an endoscopic swept source optical coherence tomography (SSOCT) system. The endoscopic SSOCT system is composed of a high speed SSOCT, a fast scanning rotational microelectromechanical system (MEMS) probe and real time data acquisition and imaging processing. The 2.2 mm rotational MEMS probe was miniature enough to be able to fit into the 2.8 mm biopsy channel of a standard endoscope. The gastrointestinal tracts of patients were imaged together with normal endoscopic examination. The epithelial, mucosal, lamina propria, and submucosal layers can be clearly seen on the OCT images.
The practical limitation of in vivo multiphoton excitation microscopy (MPM) is the lack of a compact and flexible probe.
Most MPM depends on the bench-top microscope, which prohibits expansion of in vivo application. In this study, we
introduced a miniaturized MPM probe using a microelectromechanical system (MEMS) scanning mirror and a doubleclad
photonic crystal fiber (DCPCF). Benefits from both a MEMS mirror and a DCPCF overcome current obstacles for
probe development, such as size reduction, rapid scanning, efficient delivery of short pulses, and high collection rate of
fluorescent signals. In this study, the completed probe was 1 cm in outer diameter and 14 cm in length. The probe was
then integrated to the MPM system and used to image fluorescent beads, paper and biological specimens.
KEYWORDS: Optical coherence tomography, Injuries, Control systems, Fiber optics, Blood, In vivo imaging, Animal model studies, Cartilage, Scanning electron microscopy, GRIN lenses
Optical coherence tomography (OCT) is a micron scale high-resolution optical technology that can provide real-time in vivo images noninvasively. The ability to detect airway mucosal and submucosal injury rapidly will be valuable for a range of pulmonary applications including assessment of acute inhalation smoke and burn injury. OCT has the potential ability to monitor the progression of airway injury changes including edema, hyperemia, and swelling, which are critical clinical components of smoke-inhalation injury. New Zealand white male rabbits exposed to cold smoke from standardized unbleached burned cotton administered during ventilation were monitored for 6 h using a 1.8-mm diameter flexible fiberoptic longitudinal probe that was inserted through the endotracheal tube. The thickness of the epithelial, mucosal, and submucosal layers of the rabbit trachea to the tracheal cartilage was measured using a prototype superluminescent diode OCT system we constructed. OCT was able to detect significant smoke-injury-induced increases in the thickness of the tracheal walls of the rabbit beginning very shortly after smoke administration. Airway wall thickness increased to an average of 120% (±33%) of baseline values by 5 h following exposure. OCT is capable of providing real-time, noninvasive images of airway injury changes following smoke exposure. These studies suggest that OCT may have the ability to provide information on potential early indicators of impending smoke-inhalation-induced airway compromise.
Photodisruption of femtosecond laser at 1700nm wavelength has been demonstrated
as a potential subsurface surgical method that can be used in trabeculectomy for
glaucoma treatment without causing failure due to scarring at the level of conjunctiva
and underlying tissue [1, 2]. In this study, Fourier domain optical coherence
tomography (FD-OCT) technology is used to demonstrate high speed non-invasive
imaging of high precision photodisruption in human sclera. Photodisruption cavities
of different size in human sclera can reveal itself in its 3D FDOCT image. Transclera
channel cut from back to surface and partial transclera channel are easily identified in
3D OCT image. The whole 3D data set acquired with high speed frequency domain
OCT system permits further quantitative analysis of subsurface phtodisruption
incisions. The preliminary results indicate that high speed frequency domain OCT
system is a good candidate for imaging subsurface photodisruption with femtosecond
laser and its 3D image may provide good guidance during surgical procedures when it
is integrated with laser ablation system.
We used continuum generated in an 8.5 cm long fiber by a femtosecond Yb fiber laser to improve threefold the axial resolution of frequency domain SH-OCT to 12&mgr;m. The acquisition time was shortened by more than two orders of magnitude compared to time domain SH-OCT. The system was applied to image biological tissue of fish scales, pig leg tendon and rabbit eye sclera. Highly organized collagen fibrils can be visualized in the recorded images. Polarization dependence on second harmonic has been used to obtain polarization resolved images.
We report the development of a frequency domain second harmonic OCT system. The system uses a 170 fs pulses from Yb fiber laser and second harmonic spectrum is recorded by a 0.17 nm resolution spectrometer and thermoelectric cooled CCD detector. The system is applied to image biological tissue of the fish scales. Highly organized collagen fibrils can be visualized in the recorded images. The axial resolution of the frequency domain SH-OCT is 30 μm.
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