Angelique Kano

Design and demonstration of a miniature catheter for a confocal microendoscope

The fluorescence confocal microendoscope provides high-resolution, in vivo imaging of cellular pathology during optical biopsy. The confocal microendoscope employs a flexible fiber-optic catheter coupled to a custom-built slit-scan confocal microscope. The catheter consists of a fiber-optic imaging bundle linked to a miniature objective and focus assembly. The 3-mm-diameter catheter may be used on its own or routed though the instrument channel of a commercial endoscope, adding microscopic imaging capability to conventional endoscopy. The design and performance of the miniature objective and focus assembly are discussed. Primary applications of the system include diagnosis of disease in the gastrointestinal tract and female reproductive system.

Spectral background and transmission characteristics of fiber optic imaging bundles

The emission and transmission properties of three commercially produced coherent fiber optic imaging bundles were evaluated. Full fluorescence excitation versus emission data were collected from 250 to 650 nm excitation for high-resolution Sumitomo, Fujikura, and Schott fiber bundles. The results generated show regions of autofluorescence and inelastic Raman scattering in the imaging bundles that represent a wavelength-dependent background signal when these fibers are used for imaging applications. The high-resolution fiber bundles also exhibit significant variation in transmission with the angle of illumination, which affects the overall coupling and transmission efficiency. Knowledge of these properties allows users of high-resolution imaging bundles to optimally design systems that utilize such bundles.

Development of a fiber-optic confocal microendoscope for clinical endoscopy

A confocal micro endoscope has been developed to examine cellular pathology during optical biopsy. The system employs a flexible fiber optic catheter coupled to a slit-scan confocal microscope to image tissue at remote locations in the body. The catheter of the confocal micro endoscope consists of a fiber-optic imaging bundle, a miniature objective, and a miniature focusing mechanism. The system has a lateral resolution of 1.8 micrometers and an axial resolution of 25 micrometers . The confocal micro endoscope can operate in a grayscale or multi-spectral imaging mode. Extensive work has been done to design a new miniature objective and focusing mechanism that will allow the catheter to be routed through the therapeutic channel of a clinical endoscope. We present the design for a miniature F/1 achromatic objective with nearly diffraction limited performance. The objective will be coupled to a pneumatic focusing mechanism to provide focus control to 200 micrometers below the surface of the tissue. The new catheter has an overall diameter of 3mm with a rigid tip of only 20mm in length.

In vivo fluorescence confocal microendoscopy

A catheter-based fluorescence confocal microendoscope has been developed for in vivo imaging. The catheter in this system consists of a coherent fiber-optic imaging bundle, a miniature objective, and a focus mechanism. The proximal end of the catheter is coupled to a slit-scan confocal microscope so that high-resolution fluorescence images of cells and tissue microstructure can be viewed in real-time. The performance of the microendoscope is limited by the characteristics of the fiber bundle. The lateral resolution of the system is 1.8 microns and the axial resolution is 25 microns. The field of view is 430 microns. The maximum imaging depth, is around 200 microns below the tissue surface, but this depends on the tissue properties and wavelength range of operation. The slit-scan confocal microscope allows both gray-scale imaging at 8 frames per second and multi-spectral imaging. The frame rate in the multi-spectral imaging mode is determined by the number of spectral channels. The system has been demonstrated using topically-administered exogenous fluorescence dyes in excised tissues and in vivo animal models. A new catheter is under development with a maximum diameter of 3 mm, which will allow it to be routed through the therapeutic instrument channel of a conventional clinical endoscope, making the device practical for routine clinical use.

Fiber optic confocal microendoscope as a daughter scope for clinical endoscopy

A fluorescence confocal microendoscope has been developed to provide high resolution, in-vivo imaging of cellular pathology. The microendoscope employs a fiber-optic imaging bundle, a miniature objective, and a miniature focusing mechanism to allow imaging in remote locations of the body. The system uses a 2mm diameter flexible catheter that is capped by a rigid opto-mechanical system measuring 3mm in diameter and 12mm in length. The small size of the confocal microendoscope was chosen so that it may be routed through the therapeutic channel of a clinical endoscope, adding microscopic functionality to conventional endoscopy procedures. The confocal nature of the microendoscope provides optical sectioning with 2 micron lateral resolution and 25 micron axial resolution. The pneumatic focusing mechanism located in the distal opto-mechanical assembly allows for imaging to a maximum depth of 200 micron in the tissue. The system is capable of providing conventional grayscale fluorescence images at 10 frames-per-second as well as spatially resolved multi-spectral fluorescence images at several seconds a frame. Preliminary in-vivo results are be presented.

Ultrathin single-channel fiberscopes for biomedical imaging.

Abstract. Ultrathin flexible fiberscopes typically have separate illumination and imaging channels and are available in diameters ranging from 0.5 to 2.5 mm. Diameters can potentially be reduced by combining the illumination and imaging paths into a single fiberoptic channel. Single-channel fiberscopes must incorporate a system to minimize Fresnel reflections from air–glass interfaces within the common illumination and detection path. The Fresnel reflection at the proximal surface of the fiber bundle is particularly problematic. This paper describes and compares methods to reduce the background signal from the proximal surface of the fiber bundle. Three techniques are evaluated: (1) antireflective (AR)-coating the proximal face of the fiber, (2) incorporating crossed polarizers into the light path, and (3) a novel technique called numerical aperture sharing, whereby a portion of the image numerical aperture is devoted to illumination and a portion to detection.

Microendoscopes for imaging of the pancreas

Patients diagnosed with pancreatic cancer have a 5-year survival rate of only 3%. Endoscopic imaging of the pancreas is limited by the small size of the pancreatic duct, which has an average size of 3 mm. To improve imaging capabilities for the pancreatic duct, two small catheter-based imaging systems have been developed that will fit through the therapeutic channel of a clinical endoscope and into the pancreatic duct. One is a miniature endoscope designed to provide macro-imaging of tissue with both white light reflectance and fluorescence imaging modes. The 1.75 mm diameter catheter consists of separate illumination and imaging channels. At a nominal focal distance of 10 mm, the field of view of the system is ~ 10 mm, and the corresponding in-plane resolution is 60 microns. To complement the broadfield view of the tissue, a confocal microendoscope with 2 micron lateral resolution over a field of view of 450 microns and 25 micron axial resolution has been developed. With an outer diameter of 3 mm, the catheter in this system will also fit through the therapeutic channel and into the pancreatic duct. Images of tissue with both the miniature endoscope and confocal microendoscope are presented.

Broadband endoscopic imaging through a single fiberoptic channel

An ultrathin fiberscope that incorporates illumination and detection into a single channel is presented for broadband diffuse reflectance imaging. It consists of a 0.5 mm diameter imaging catheter (coherent fiber bundle cemented to a grin lens), illumination and collection optics, and a ccd camera. To obtain reasonable image contrast, surface scatter and the specular reflections at interfaces of differing refractive index must be reduced. In this paper, the prototype system is modeled end-to-end in a non-sequential ray tracing program with the aim of locating sources of residual backscatter and backreflections. Analysis of results from two test objects, text and tissue, are presented.

Confocal microendoscope for use in OB/GYN applications

A 3 mm catheter-based fluorescence confocal microscope has been developed for in vivo use. The catheter in this system fits through the therapeutic channel of a commercial endoscope. The catheter consists of a coherent fiber-optic imaging bundle, a miniature objective, and a focusing mechanism. The proximal end of the catheter is coupled to a slit-scan confocal microscope. Real-time images can be obtained of fluorescing tissue microstructures. The optical performance of the microendoscope is limited by the characteristics of the fiber bundle. The lateral resolution is 1.8 /spl mu/m and the axial resolution is 25 /spl mu/m. The field of view is 430 /spl mu/m. The maximum imaging depth is 200 /spl mu/m. The confocal microscope operates in both grayscale and multispectral modes. Images have been obtained of in vivo animal models and ex vivo human models. A portable confocal microscope system is under development for in vivo clinical evaluation.

Fluorescence endoscopic imaging of the pancreas

Current endoscopic instrumentation for imaging the pancreas is limited by the small size of the pancreatic duct. A small catheter-based system for imaging the inside of the pancreatic duct has been developed. The endoscopic system combines both fluorescence and white-light reflectance imaging modes.