The diagnostic potential of autofluorescence (AF) microscopy under ultraviolet (UV) excitation is explored using ex vivo human specimens. The aim is to establish optical patterns (the rules for interpretation) that correspond to normal and abnormal histologies of the esophagus, spanning from early benign modifications (Barrett's esophagus) to subsequent dysplastic change and progression toward carcinoma. This was achieved by developing an image library categorized by disease progression. We considered morphological changes of disease as they are compared with histological diagnosis of the pathological specimen, as well as control samples of normal esophagus, proximal stomach, and small intestine tissue. Our experimental results indicate that UV AF microscopy could provide real-time histological information for visualizing changes in tissue microstructure that are currently undetectable using conventional endoscopic methods.
We explore autofluorescence endomicroscopy as a potential tool for real-time visualization of epithelial tissue microstructure and organization in a clinical setting. The design parameters are explored using two experimental systems-an Olympus Medical Systems Corp. stand-alone clinical prototype probe, and a custom built bench-top rigid fiber conduit prototype. Both systems entail ultraviolet excitation at 266 nm and/or 325 nm using compact laser sources. Preliminary results using ex vivo animal and human tissue specimens suggest that this technology can be translated toward in vivo application to address the need for real-time histology.
The potential of autofluorescence microscopy under ultraviolet excitation is investigated as a method to visualize
superficial epithelial microstructures and their modification with progression of disease. This method does not require
the use of contrast agents, sectioning methods, or tissue preparation. Imaging of esophagus tissue is the focus of this
study and deals with three main issues: a) What is the origin of the signal; b) How the gradual microstructure
modification associated with various stages of esophageal disease is visualized; c) What are the designing parameters
for in vivo implementation.
The non-invasiveness of autofluorescence technology may reduce sampling error and time delay for histopathology
diagnosis. We establish biophotonic methods and guidelines to visualize and interpret early epithelial tissue changes that
signify disease. Flexible and rigid fiber endomicroscopy instrumentation design parameters feasible for translation
towards clinical use are in development.
Epithelial microstructures related to early stage carcinoma are currently invisible to traditional white light endoscopy.
We recently demonstrated that autofluorescence microscopy under ultraviolet excitation can visualize superficial
microstructures without the use of contrast agents, sectioning methods, or tissue preparation. Spectroscopic analysis
allowed a better understanding of autofluorescence signal characteristics at the microscopic level and the mechanism for
achieving high quality imaging of the superficial epithelial layer with conventional wide-field microscopy. The
designing parameters for the adaptation of this technology into an endoscope probe for real-time in vivo microscopy are
tested using a bench-top prototype system. This approach may provide a powerful tool for the detection and staging of
carcinomas.
NIR light scattering from ex vivo porcine cardiac tissue was investigated to understand how imaging or point
measurement approaches may assist development of methods for tissue depth assessment. Our results indicate an
increase of average image intensity as thickness increases up to approximately 2 mm. In a dual fiber spectroscopy
configuration, sensitivity up to approximately 3 mm with an increase to 6 mm when spectral ratio between selected
wavelengths was obtained. Preliminary Monte Carlo results provided reasonable fit to the experimental data.
We explore imaging of tissue microstructures using autofluorescence and light scattering methods implemented through a hyperspectral microscope design. This system utilizes long working distance objectives that enable off-axis illumination of tissue thereby allowing for excitation at any optical wavelength without requiring change of optical elements within the microscope. Spectral and polarization elements are easily and rapidly incorporated to take
advantage of spectral variations of spectroscopic optical signatures for enhanced contrast. The collection efficiency has been maximized such that image acquisition may be acquired within very short exposure times, a key feature for transferring this technology to a clinical setting. Preliminary studies using human and animal tissues demonstrate the feasibility of this approach for real-time imaging of intact tissues as they would appear in the operating room.
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