Joshua A. Udovich

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.

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.

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.

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.

Intraoperative fluorescent imaging of intracranial tumors: A review

A review of fluorescent imaging for intracranial neoplasms is presented. Complete resection of brain cancer is seldom possible because of the goal to preserve brain tissue and the inability to visualize individual infiltrative tumor cells. Verification of histology and identification of tumor invasion in macroscopically normal-appearing brain tissue determine prognosis after resection of malignant gliomas. Therefore, imaging modalities aim to facilitate intraoperative decision-making. Intraoperative fluorescent imaging techniques have the potential to enable precise histopathologic diagnosis and to detect tumor remnants in the operative field. Macroscopic fluorescence imaging is effective for gross tumor detection. Microscopic imaging techniques enhance the sensitivity of the macroscopic observations and provide real-time histological information. Further development of clinical grade fluorescent agents specifically targeting tumor cells could improve the diagnostic and prognostic yield of intraoperative imaging.

Assessment of Acridine Orange and SYTO 16 for in vivo imaging of the peritoneal tissues in mice

The effect of peritoneal injection of acridine orange and SYTO 16 in mice was investigated. Images of peritoneal tissues stained with these dyes and obtained through a confocal micro‐endoscope are presented. Seventy‐five Balb/c mice were split into five groups and given peritoneal injections of dye or saline. The proportions of negative outcomes in each group were compared using confidence intervals and the Fishers exact statistical test. A statistically significant increase in adverse events due to dye injection was not observed. These data provide an initial investigation into the safety of acridine orange and SYTO 16 for in vivo imaging.

Design of an in vivo multi-spectral confocal microendoscope for clinical trials

We previously reported on the development and testing of a multi-spectral confocal microendoscope. Here we present a new system that will be used during an early stage clinical trial. The new microendoscope is significantly smaller, uses fewer optical elements, and is structurally more robust. The slit-scanning confocal system employs two synchronized single-axes scan mirrors and an externally coupled imaging catheter with automated focus control and dye delivery systems. In grayscale collection mode the confocal microendoscope operates at 30 frames-per-second with 3μm lateral resolution and 25μm axial resolution. The multi-spectral collection mode operates at 0.5 frames-per-second when acquiring 32 spectral channels with an average minimum resolvable wavelength difference of 12nm. The system will be used, in grayscale mode, to image ovaries during a small scale clinical trial on women undergoing oophorectomy. Recent grayscale and multi-spectral imaging results from ex-vivo human tissues are presented.

In-vivo multi-spectral confocal microscopy

A multi-spectral confocal microendoscope (MCME) for in-vivo imaging has been developed. The MCME employs a flexible fiber-optic catheter coupled to a slit-scan confocal microscope with an imaging spectrometer. The catheter consists of a fiber-optic imaging bundle linked to a miniature objective and focus assembly. The focus mechanism allows for imaging to a maximum tissue depth of 200 microns. The 3mm diameter catheter may be used on its own or routed though the instrument channel of a commercial endoscope. The confocal nature of the system provides optical sectioning with 3 micron lateral resolution and 30 micron axial resolution. The system incorporates two laser sources and is therefore capable of simultaneous acquisition of spectra from multiple dyes using dual excitation. The prism based multi-spectral detection assembly is typically configured to collect 30 spectral samples over the visible range. The spectral sampling rate varies from 4nm/pixel at 490nm to 8nm/pixel at 660nm and the minimum resolvable wavelength difference varies from 8nm to 16nm over the same spectral range. Each of these characteristics are primarily dictated by the dispersion characteristics of the prism. The MCME is designed to examine cellular structures during optical biopsy and to exploit the diagnostic information contained within the spectral domain. The primary applications for the system include diagnosis of disease in the gastro-intestinal tract and female reproductive system. In-vitro, and ex-vivo multi-spectral results are presented.

Confocal microendoscope for use in a clinical setting

A mobile confocal microendoscope for use in a clinical setting has been developed. This system employs an endoscope consisting of a custom designed objective lens with a fiber optic imaging bundle to collect in-vivo images of patients. Some highlights and features of this mobile system include frame rates of up to 30 frames per second, an automated focus mechanism, automated dye delivery, clinician control, and the ability to be used in an area where there is a single 110V outlet. All optics are self-contained and the entire enclosure and catheter can be moved between surgical suites, sterilized and brought online in under 15 minutes. At this time, all data have been collected with a 488 nm laser, but the system is able to have a second laser line added to provide additional imaging capability. Preliminary in vivo results of images from the ovaries using topical fluorescein as a contrast agent are shown. Future plans for the system include use of acridine orange (AO) or SYTO-16 as a nucleic acid stain.

Confocal Microendoscopy: An Emerging Tool for in situ Disease Diagnosis

The confocal microendoscope is an instrument for optical biopsy that allows in situ imaging of tissue at the cellular level. Several promising clinical applications are emerging for this type of novel instrumentation.