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 second-harmonic optical coherence tomography (SH-OCT) to 12 microm. The acquisition time was shortened by more than 2 orders of magnitude compared to the 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 the SH has been used to obtain polarization resolved images.

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.

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. © 2011 Copyright SPIE - The International Society for Optical Engineering.

Background

Intravascular optical coherence tomography (OCT) is a recently developed optical imaging technique that provides high-resolution cross-sectional in situ images from intact tissue based on tissue reflectance of near-infrared or infrared light.

Objective

To report on the feasibility of neuroendovascular OCT imaging and compare the neuroendovascular OCT findings with histology in nondiseased vessels in an animal, cadaveric, and clinical study.

Methods

Catheter-based in vivo endovascular OCT imaging was performed in the common carotid arteries of 2 pigs and in the intracranial carotid arteries of 3 patients. The endovascular OCT device was delivered to the desired location via groin access and using standard endovascular procedures. Images were obtained via rotational and translational scanning using external motors. In vivo findings were reproduced using ex vivo OCT imaging in corresponding animal and human (cadaveric) harvested tissue segments. These segments underwent histological examination for comparison.

Results

The structural compositions of the OCT-imaged segments of the common carotid arteries in pigs as well as the petrous and cavernous intracranial carotid arteries in patients were visualized at high resolution (8 μm). The in vivo images were identical to those obtained ex vivo, demonstrating the imaging capabilities of the endovascular OCT device. The OCT images correlated well with the images obtained after histological sectioning and visualized in vivo the laminar vascular structure.

Conclusion

Neuroendovascular OCT imaging is feasible for clinical use and can detect with high resolution the structure of arterial segments. Understanding OCT imaging in nondiseased arteries is important in establishing baseline findings necessary for interpreting pathological processes. This allows neuroendovascular optical biopsies of vascular tissue to be obtained without the need for excision and processing.

Objective

To demonstrate the feasibility of performing optical coherence tomography of the human larynx on the awake patient with a novel flexible fiberoptic delivery system.

Study design

Prospective clinical trial.

Subjects and methods

Imaging was performed in 17 awake patients. A flexible optical coherence tomography probe was inserted through the nose and placed in near or gentle contact with laryngeal tissues under direct endoscopic visualization.

Results

Images were successfully obtained from all laryngeal subsites and clearly identified laryngeal mucosal microanatomy. Several critical probe design modifications improved rotational and angular control of the distal tip while allowing linear translation of the probe and allowing more accurate apposition of the probe onto target tissues, which is critical for transnasal laryngeal imaging.

Conclusion

This study demonstrates the feasibility of awake transnasal laryngeal optical coherence tomography and identifies key instrumentation needed to obtain useful images.

We present multiphoton microendoscopy with a rotational probe and a 1 microm fiber-based femtosecond laser. The rotational probe is based on a double-clad photonic crystal fiber, a gradient index lens, a microprism, and a rotational microelectronicmechanical system (MEMS) motor. The MEMS motor has a diameter of 2.2 mm and can provide 360 degrees full-view rotation. The fiber laser provides ultrashort pulses with a central wavelength at 1.034 microm and a repetition rate of 50 MHz. Second-harmonic-generation images of rat-tail tendon and fish scale are demonstrated with the rotational probe-based multiphoton 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.

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.