Anthony A. Tanbakuchi

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.

Adaptive pixel defect correction

Although the number of pixels in image sensors is increasing exponentially, production techniques have only been able to linearly reduce the probability that a pixel will be defective. The result is a rapidly increasing probability that a sensor will contain one or more defective pixels. Sensors with defects are often discarded after fabrication because they may not produce aesthetically pleasing images. To reduce the cost of image sensor production, defect correction algorithms are needed that allow the utilization of sensors with bad pixels. We present a relatively simple defect correction algorithm, requiring only a small 7 by 7 kernel of raw color filter array data that effectively corrects a wide variety of defect types. Our adaptive edge algorithm is high quality, uses few image lines, is adaptable to a variety of defect types, and independent of other on-board DSP algorithms. Results show that the algorithm produces substantially better results in high-frequency image regions compared to conventional one-dimensional correction methods.

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.

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.

Surgical imaging catheter for confocal microendoscopy with advanced contrast delivery and focus systems

We present a laparoscope for fluorescence confocal microendoscopy specifically designed for microscopic imaging during diagnostic laparoscopic surgery. The catheter consists of a disposable rigid distal tip which houses a flexible microendoscope and dye channel. The laparoscopic tip is a small disposable polycarbonate sheath containing two inner lumens with a glass window on the distal end. The sheath outer diameter suitable for use in a 5mm trocar. The smaller inner lumen provides a channel for delivering fluorescent contrast agents to the tissue through a 200um hole in the glass window. On the proximal end, the smaller lumen is coupled to a computer controlled fluid delivery system that controls the amount of contrast agent dispensed onto the tissue down to a fraction of a micro liter. The main lumen houses the microendoscope. The microendoscope incorporates a computer-controlled focus mechanism that can quickly and accurately focus while correcting for hysteresis. This fluorescence confocal micro-laparoscope will be tested in a small-scale clinical trial on women undergoing oophorectomy in the near future.

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.

Clinical evaluation of a confocal microendoscope system for imaging the ovary

We have developed a mobile confocal microendoscope system that provides live cellular imaging during surgery to aid in diagnosing microscopic abnormalities including cancer. We present initial clinical trial results using the device to image ovaries in-vivo using fluorescein and ex-vivo results using acridine orange. The imaging catheter has improved depth control and localized dye delivery mechanisms than previously presented. A manual control now provides a simple way for the surgeon to adjust and optimize imaging depth during the procedure while a tiny piezo valve in the imaging catheter controls the dye delivery.

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.