Improvement in optical fiber bundle-based imaging using synchronized fiber motion.

Image quality in fiber bundle-based imaging systems is inherently limited by the size and spacing of the individual fiber cores. The fiber bundle limits the achievable spatial resolution and superimposes a fixed pattern of signal variability across the image. To overcome these limitations, piezoelectric tubes were used to synchronously dither the fiber bundle on both ends. Experimental results using the dithering approach with a commercial fiber bundle showed a substantial decrease in fixed pattern noise and an increase in spatial resolution.

Pilot Clinical Evaluation of a Confocal Microlaparoscope for Ovarian Cancer Detection.

OBJECTIVE: The aim of this study is to evaluate the performance of a confocal fluorescence microlaparoscope for in vivo detection of ovarian cancer. METHODS/MATERIALS: Seventy-one patients scheduled for open or laparoscopic oophorectomy were consented for the imaging study. High-resolution confocal microlaparoscopic images of the epithelial surface of the ovary were acquired in vivo or ex vivo after tissue staining using acridine orange. Standard histologic evaluation of extracted tissue samples was performed and used as the gold standard of disease diagnosis. Trained human observers from different specialties viewed the microlaparoscopic images, rating each image on a 6-point scale ranging from "definitely not cancer" to "definitely cancer." Receiver operating characteristic curves were generated using these scores and the gold standard histopathologic diagnosis. Area under the receiver operating characteristic curve (AUC) was calculated as a performance metric. RESULTS: Forty-five of the consented patients were used in the final evaluation study. From these 45 patients, 63 tissue locations or samples were identified and imaged with the confocal microlaparoscope. Twenty of the samples were high-grade cancers, and the remaining 43 samples were normal or noncancerous. Twenty-three of the samples were imaged in vivo, and the remaining 40 samples were imaged ex vivo. The average AUC score and standard error (SE) for detection of cancer in all images were 0.88 and 0.02, respectively. An independent-samples t test was conducted to compare AUC scores for in vivo and ex vivo conditions. No statistically significant difference in the AUC score for in vivo (AUC, 0.850; SE, 0.049) and ex vivo (AUC, 0.888; SE, 0.027) conditions was observed, t(6) = 1.318, P = 0.2355. CONCLUSIONS: Area under the receiver operating characteristic curve scores indicate that high-resolution in vivo images obtained by the confocal laparoscope can distinguish between normal and malignant ovarian surface epithelium. In addition, in vivo performance is similar to that which can be obtained from ex vivo tissue.

Analysis of multimode fiber bundles for endoscopic spectral-domain optical coherence tomography.

A theoretical analysis of the use of a fiber bundle in spectral-domain optical coherence tomography (OCT) systems is presented. The fiber bundle enables a flexible endoscopic design and provides fast, parallelized acquisition of the OCT data. However, the multimode characteristic of the fibers in the fiber bundle affects the depth sensitivity of the imaging system. A description of light interference in a multimode fiber is presented along with numerical simulations and experimental studies to illustrate the theoretical analysis.

Using FDA-approved drugs as off-label fluorescent dyes for optical biopsies: from in silico design toex vivoproof-of-concept.

Optical biopsies bring the microscope to the patient rather than the tissue to the microscope, and may complement or replace the tissue-harvesting component of the traditional biopsy process with its associated risks. In general, optical biopsies are limited by the lack of endogenous tissue contrast and the small number of clinically approvedin vivodyes. This study tests multiple FDA-approved drugs that have structural similarity to research dyes as off-labelin situfluorescent alternatives to standardex vivohematoxylin & eosin tissue stain. Numerous drug-dye combinations shown here may facilitate relatively safe and fastin situor possiblyin vivostaining of tissue, enabling real-time optical biopsies and other advanced microscopy technologies, which have implications for the speed and performance of tissue- and cellular-level diagnostics.

In vivo imaging of ovarian tissue using a novel confocal microlaparoscope.

OBJECTIVE: The objective of the study was to develop a clinical confocal microlaparoscope for imaging ovary epithelium in vivo with the long-term objective of diagnosing cancer in vivo. STUDY DESIGN: A confocal microlaparoscope was developed and used to image the ovaries of 21 patients in vivo using fluorescein sodium and acridine orange as the fluorescent contrast agents. RESULTS: The device was tested in vivo and demonstrated to be safe and function as designed. Real-time cellular visualization of ovary epithelium was demonstrated. CONCLUSION: The confocal microlaparoscope represents a new type of in vivo imaging device. With its ability to image cellular details in real time, it has the potential to aid in the early diagnosis of cancer. Initially the device may be used to locate unusual regions for guided biopsies. In the long term, the device may be able to supplant traditional biopsies and allow the surgeon to identify early-stage ovarian cancer.

Investigation of confocal microscopy for differentiation of renal cell carcinoma versus benign tissue. Can an optical biopsy be performed?

OBJECTIVE: Novel optical imaging modalities are under development with the goal of obtaining an "optical biopsy" to efficiently provide pathologic details. One such modality is confocal microscopy which allows in situ visualization of cells within a layer of tissue and imaging of cellular-level structures. The goal of this study is to validate the ability of confocal microscopy to quickly and accurately differentiate between normal renal tissue and cancer. METHODS: Specimens were obtained from patients who underwent robotic partial nephrectomy for renal mass. Samples of suspected normal and tumor tissue were extracted from the excised portion of the kidney and stained with acridine orange. The stained samples were imaged on a Nikon E600 C1 Confocal Microscope. The samples were then submitted for hematoxylin and eosin processing and read by an expert pathologist to provide a gold-standard diagnosis that can later be compared to the confocal images. RESULTS: This study included 11 patients, 17 tissue samples, and 118 confocal images. Of the 17 tissue samples, 10 had a gold-standard diagnosis of cancer and seven were benign. Of 118 confocal images, 66 had a gold-standard diagnosis of cancer and 52 were benign. Six confocal images were used as a training set to train eight observers. The observers were asked to rate the test images on a six point scale and the results were analyzed using a web based receiver operating characteristic curve calculator. The average accuracy, sensitivity, specificity, and area under the empirical receiver operating characteristic curve for this study were 91%, 98%, 81%, and 0.94 respectively. CONCLUSION: This preliminary study suggest that confocal microscopy can be used to distinguish cancer from normal tissue with high sensitivity and specificity. The observers in this study were trained quickly and on only six images. We expect even higher performance as observers become more familiar with the confocal images.

Multispectral confocal microendoscope for in vivo and in situ imaging.

We describe the design and operation of a multispectral confocal microendoscope. This fiber-based fluorescence imaging system consists of a slit-scan confocal microscope coupled to an imaging catheter that is designed to be minimally invasive and allow for cellular level imaging in vivo. The system can operate in two imaging modes. The grayscale mode of operation provides high resolution real-time in vivo images showing the intensity of fluorescent signal from the specimen. The multispectral mode of operation uses a prism as a dispersive element to collect a full multispectral image of the fluorescence emission. The instrument can switch back and forth nearly instantaneously between the two imaging modes (less than half a second). In the current configuration, the multispectral confocal microendoscope achieves 3-microm lateral resolution and 30-microm axial resolution. The system records light from 500 to 750 nm, and the minimum resolvable wavelength difference varies from 2.9 to 8.3 nm over this spectral range. Grayscale and multispectral imaging results from ex-vivo human tissues and small animal tissues are presented.

Computer-aided identification of ovarian cancer in confocal microendoscope images.

The confocal microendoscope is an instrument for imaging the surface of the human ovary. Images taken with this instrument from normal and diseased tissue show significant differences in cellular distribution. A real-time computer-aided system to facilitate the identification of ovarian cancer is introduced. The cellular-level structure present in ex vivo confocal microendoscope images is modeled as texture. Features are extracted based on first-order statistics, spatial gray-level-dependence matrices, and spatial-frequency content. Selection of the features is performed using stepwise discriminant analysis, forward sequential search, a nonparametric method, principal component analysis, and a heuristic technique that combines the results of these other methods. The selected features are used for classification, and the performance of various machine classifiers is compared by analyzing areas under their receiver operating characteristic curves. The machine classifiers studied included linear discriminant analysis, quadratic discriminant analysis, and the k-nearest-neighbor algorithm. The results suggest it is possible to automatically identify pathology based on texture features extracted from confocal microendoscope images and that the machine performance is superior to that of a human observer.

Confocal microlaparoscope for imaging the fallopian tube.

Recent evidence suggests that ovarian cancer can originate in the fallopian tube. Unlike many other cancers, poor access to the ovary and fallopian tubes has limited the ability to study the progression of this deadly disease and to diagnosis it during the early stage when it is most amenable to therapy. A rigid confocal microlaparoscope system designed to image the epithelial surface of the ovary in vivo was previously reported. A new confocal microlaparoscope with an articulating distal tip has been developed to enable in vivo access to human fallopian tubes. The new microlaparoscope is compatible with 5-mm trocars and includes a 2.2-mm-diameter articulating distal tip consisting of a bare fiber bundle and an automated dye delivery system for fluorescence confocal imaging. This small articulating device should enable the confocal microlaparoscope to image early stage ovarian cancer arising inside the fallopian tube. Ex vivo images of animal tissue and human fallopian tube using the new articulating device are presented along with in vivo imaging results using the rigid confocal microlaparoscope system.

Design and Performance of a Multi-Point Scan Confocal Microendoscope.

Confocal fluorescence microendoscopy provides high-resolution cellular-level imaging via a minimally invasive procedure, but requires fast scanning to achieve real-time imaging in vivo. Ideal confocal imaging performance is obtained with a point scanning system, but the scan rates required for in vivo biomedical imaging can be difficult to achieve. By scanning a line of illumination in one direction in conjunction with a stationary confocal slit aperture, very high image acquisition speeds can be achieved, but at the cost of a reduction in image quality. Here, the design, implementation, and experimental verification of a custom multi-point aperture modification to a line-scanning multi-spectral confocal microendoscope is presented. This new design improves the axial resolution of a line-scan system while maintaining high imaging rates. In addition, compared to the line-scanning configuration, previously reported simulations predicted that the multi-point aperture geometry greatly reduces the effects of tissue scatter on image quality. Experimental results confirming this prediction are presented.

Ultrathin single-channel fiberscopes for biomedical imaging.

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.

Dual modality fluorescence confocal and spectral-domain optical coherence tomography microendoscope.

Optical biopsy facilitates in vivo disease diagnoses by providing a real-time in situ view of tissue in a clinical setting. Fluorescence confocal microendoscopy and optical coherence tomography (OCT) are two methods that have demonstrated significant potential in this context. These techniques provide complementary viewpoints. The high resolution and contrast associated with confocal systems allow en face visualization of sub-cellular details and cellular organization within a thin layer of biological tissue. OCT provides cross-sectional images showing the tissue micro-architecture to a depth beyond the reach of confocal systems. We present a novel design for a bench-top imaging system that incorporates both confocal and OCT modalities in the same optical train allowing the potential for rapid switching between the two imaging techniques. Preliminary results using simple phantoms show that it is possible to realize both confocal microendoscopy and OCT through a fiber bundle based imaging system.

Monte Carlo characterization of parallelized fluorescence confocal systems imaging in turbid media.

We characterize and compare the axial and lateral performance of fluorescence confocal systems imaging in turbid media. The aperture configurations studied are a single pinhole, a slit, a Nipkow disk, and a linear array of pinholes. Systems with parallelized apertures are used clinically because they enable high-speed and real-time imaging. Understanding how they perform in highly scattering tissue is important. A Monte Carlo model was developed to characterize parallelized system performance in a scattering media representative of human tissues. The results indicate that a slit aperture has degraded performance, both laterally and axially. In contrast, the analysis reveals that multipinhole apertures such as a Nipkow disk or a linear pinhole array can achieve performance nearly equivalent to a single pinhole aperture. The optimal aperture spacing for the multipinhole apertures was determined for a specific tissue model. In addition to comparing aperture configurations, the effects of tissue nonradiative absorption, scattering anisotropy, and fluorophore concentration on lateral and axial performance of confocal systems were studied.

Clinical confocal microlaparoscope for real-time in vivo optical biopsies.

Successful treatment of cancer is highly dependent on the stage at which it is diagnosed. Early diagnosis, when the disease is still localized at its origin, results in very high cure rates-even for cancers that typically have poor prognosis. Biopsies are often used for diagnosis of disease. However, because biopsies are destructive, only a limited number can be taken. This leads to reduced sensitivity for detection due to sampling error. A real-time fluorescence confocal microlaparoscope has been developed that provides instant in vivo cellular images, comparable to those provided by histology, through a nondestructive procedure. The device includes an integrated contrast agent delivery mechanism and a computerized depth scan system. The instrument uses a fiber bundle to relay the image plane of a slit-scan confocal microlaparoscope into tissue. It has a 3-mum lateral resolution and a 25-mum axial resolution. Initial in vivo clinical testing using the device to image human ovaries has been done in 21 patients. Results indicate that the device can successfully image organs in vivo without complications. Results with excised tissue demonstrate that the instrument can resolve sufficient cellular detail to visualize the cellular changes associated with the onset of cancer.

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.