Showing papers by "Brett E. Bouma published in 1998"

Methods and apparatus for forward-directed optical scanning instruments

Abstract: An imaging system for performing forward scanning imaging for application to therapeutic and diagnostic devises used in medical procedures. The imaging system includes forward directed optical coherence tomography (OCT), and non-retroreflected forward scanning OCT. Also interferometric imaging and ranging techniques and fluorescent, Raman, two-photon, and diffuse wave imaging can be used. The forward scanning mechanisms include a cam attached to a motor, pneumatic devices, a pivoting device, piezoelectric transducers, electrostatic driven slides for substantially transverse scanning; counter-rotating prisms, and offset lenses are used for arbitrary scanning. The imaging system of the invention is applied to hand held probes including probes integrated with surgical probes, scalpels, scissors, forceps and biopsy instruments. Hand held probes include forward scanning lasers. The imaging system is also applicable to laparoscopes and endoscopes for diagnostc and therapeutic intervention in body orifices, canals, tubes, ducts, vessels and cavities of the body. The imaging system includes application to surgical and high numerical aperture microscopes. An important application of the invention is implantation of the optical probe for periodic or continuous extraction of information from the tissue site where implanted.

Grating based phase control optical delay line

Abstract: An apparatus for performing high speed scanning of an optical delay and its application for performing optical interferometry, ranging, and imaging, including cross sectional imaging using optical coherence tomography, is disclosed. The apparatus achieves optical delay scanning by using diffractive optical elements in conjunction with imaging optics. In one embodiment a diffraction grating disperses an optical beam into different spectral frequency or wavelength components which are collimated by a lens. A mirror is placed one focal length away from the lens and the alteration of the grating groove density, the grating input angle, the grating output angle, and/or the mirror tilt produce a change in optical group and phase delay. This apparatus permits the optical group and phase delay to be scanned by scanning the angle of the mirror. In other embodiments, this device permits optical delay scanning without the use of moving parts.

Spectrally encoded confocal microscopy.

Abstract: An endoscope-compatible, submicrometer-resolution scanning confocal microscopy imaging system is presented. This approach, spectrally encoded confocal microscopy (SECM), uses a quasi-monochromatic light source and a transmission diffraction grating to detect the reflectivity simultaneously at multiple points along a transverse line within the sample. Since this method does not require fast spatial scanning within the probe, the equipment can be miniaturized and incorporated into a catheter or endoscope. Confocal images of an electron microscope grid were acquired with SECM to demonstrate the feasibility of this technique.

Intraoperative assessment of microsurgery with three-dimensional optical coherence tomography.

Abstract: PURPOSE: To evaluate three-dimensional optical coherence tomography (OCT) for use in the assessment of the microsurgical anastomoses of vessels and nerves. MATERIALS AND METHODS: OCT is an optical analogue of ultrasonography and is capable of imaging nontransparent biologic tissue by detecting backscattered infrared light. Cross-sectional in vitro images of rabbit and human vessels and nerves were obtained in as little as 125 msec at 10-micron resolution by using a solid-state laser as a light source. A surgical microscope was integrated with OCT to perform simultaneous imaging with en face visualization. Cross-sectional images were assembled to produce three-dimensional reconstructions of microsurgical specimens. RESULTS: Three-dimensional OCT reconstructions depicted the structure within an arterial anastomosis and helped identify sites of luminal obstruction. The longitudinal spatial orientation of individual nerve fascicles was tracked in three dimensions to identify changes in position. In vitro huma...

Optical Coherence Tomographic Imaging of Human Tissue at 1.55 μm and 1.81 μm Using Er- and Tm-Doped Fiber Sources.

Abstract: We demonstrate two short-coherence-length, rare-earth-doped fiber optical sources for performing optical coherence tomography (OCT) in human tissue. The first source is a stretched-pulse, mode-locked Er-doped fiber laser with a center wavelength of 1.55 μm, a power of 100 mW, and a bandwidth of 80 nm. The second is a Tm-doped silica fiber fluorescent source emitting up to 7 mW of power at 1.81 μm with a bandwidth of 80 nm. The OCT imaging depth of penetration in in vitro human aorta is compared using these sources and conventional 1.3-μm sources. © 1998 Society of Photo-Optical Instrumentation Engineers.

High resolution imaging of the upper respiratory tract with optical coherence tomography a feasibility study

Abstract: A need exists in respiratory medicine for a technology capable of identifying airway pathology on a micron scale. This study has demonstrated the feasibility of optical coherence tomography (OCT) for ultrahigh resolution imaging of the upper respiratory tract by in vitro studies of human tissue. OCT is a relatively new technique that can be used to noninvasively collect tomographic images of tissue microstructure with micron-scale resolution. OCT is analogous to ultrasound, measuring the intensity of infrared light rather than acoustical waves. Samples throughout the upper respiratory tract, from the epiglottis to the secondary bronchi, were imaged. The resulting images were compared with histopathology and verified the ability of OCT to delineate relevant structures such as the epithelium, mucosa, cartilage and its sublayers, and glands at a resolution higher than any clinical imaging technology. The ability of OCT to generate image resolution in the range close to that of histopathology in real time, as well as easy integration with small, relatively inexpensive endoscopes, low cost, and lack of a need for a transducing medium, supports the hypothesis that this optical technology could become a powerful modality in the diagnosis and management of a wide range of clinical respiratory pathology.

Optical biopsy in human pancreatobiliary tissue using optical coherence tomography

Abstract: Optical coherence tomography (OCT) is a new technique for performing high-resolution, cross-sectional tomographic imaging in human tissue. OCT is analogous to ultrasound B mode imaging except that it uses light rather than acoustical waves. As a result, OCT has over 10 times the resolution of currently available clinical high-resolution cross-sectional imaging technologies. In this work, we investigate the capability of OCT to differentiate the architectural morphology of pancreatobiliary tissues. Normal pancreatobiliary tissues, including the gallbladder, common bile duct, pancreatic duct, and pancreas were taken postmortem and imaged using OCT. Images were compared to corresponding histology to confirm tissue identity. Microstructure was delineated in different tissues, including tissue layers, glands, submucosal microvasculature, and pancreatic islets of Langerhans. The ability of OCT to provide high-resolution imaging of pancreatobiliary architectural morphology suggests the feasibility of using OCT as a powerful diagnostic endoscopic imaging technology to image early stages of pancreatobiliary disease.

Optical Biopsy with Optical Coherence Tomographya

Abstract: A need exists in medicine for a technology capable of 'optical biopsy,' imaging at or near the resolution of histopathology without the need for excisional biopsy. Optical coherence tomography (OCT) is a recently developed imaging technology that uses infrared light to generate cross-sectional images on a micron scale. In this work, the feasibility of OCT for optical biopsy was confirmed with in vitro tissue from the skeletal and male reproductive systems. This work supports the hypothesis that OCT is an attractive technology for in vivo optical biopsy.

Optical Coherence Tomographic Imaging of In Vivo Cellular Dynamics

Abstract: Optical coherence tomography (OCT) is an optical imaging technology capable of cellular resolutions. OCT is based on the detection of backscattered near infrared laser radiation and is analogous to ultrasound B-mode imaging except reflections of light are detected rather than sound. Using the Xenopus laevis (African frog) developmental biology animal model, in vivo mitotic activity of differentiating mesenchymal cells was imaged throughout the cell cycle. Individual cell nuclei and membranes were identified with OCT free-space resolutions of 5 µm. Cell migration was observed by tracking neural crest melanocytes within nontransparent Xenopus specimens which may be relevant in developmental and molecular biology. Cell morphology was confirmed with corresponding histology. Optical coherence tomography may have the potential for imaging in vivo cellular morphology in humans for the early detection of neoplastic changes.

In-vivo catheter-based imaging with optical coherence tomography

Abstract: The high incidence and mortality rate associated with complications resulting from coronary artery atherosclerosis dictate an important and immediate need for a new, high resolution, diagnostic imaging technology that would allow characterization of artery microstructure with a micron scale resolution. OCT allows catheter based, cross-sectional imaging of blood vessels with a 10-20 µm resolution and is ideally suited for in vivo imaging of arterial structure. Recently, OCT imaging was extended to in vitro pathology, including multiple studies on atherosclerotic arteries. OCT has also been directly compared with a 30 MHz, IVUS transducer. In addition to qualitatively superior resolution with respect to imaging plaque, OCT was demonstrated to be quantitatively superior. In vivo imaging was performed on normal, New Zealand White rabbits using a novel rapid data acquisition system which allows imaging at 4 frames per second. This work, focusing on dynamic changes, demonstrates that high resolution intravascular imaging can be performed in vivo using optical coherence tomography. Images at 10 µm resolution were obtained, representing an improvement of over 10X that of 'state of the art' IVUS transducers.

Real time imaging of laser intervention with optical coherence tomography

Abstract: The ability to visualize changes within tissue during surgical procedures will improve feedback to the surgeon permitting intraoperative adjustments in protocol. Optical coherence tomography (OCT) is a biomedical imaging technology based on the detection of near-infrared optical backscatter from tissue. Fast scanning optical coherence tomography, capable of imaging at 8 frames per second, is introduced for real-time monitoring of surgical interventions with micron-scale resolution. Ablation and thermal effects of argon laser exposure are examined in different tissues, illustrating one example of an interventional procedure. Integration of high-speed OCT imaging with an incisional or ablative device suggests that this technology may be useful for assessing intraoperative dynamics of tissue ablation.

Optical coherence tomography using femtosecond lasers

Abstract: Optical coherence tomography (OCT) using femtosecond lasers enables subcellular resolutions of < 5 μm and real time imaging at several frames per second. Catheter-endoscope imaging and medical applications are discussed.