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ABSTRACT: 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.
Journal of Biomedical Optics 01/2012; 17(1):016013. · 3.16 Impact Factor
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ABSTRACT: We report the diagnostic ability of ultraviolet (UV)-excited autofluorescence (AF) excitation-emission matrix (EEM) spectroscopy associated with parallel factor (PARAFAC) analysis for differentiating cancer from normal nasopharyngeal tissue. A bifurcated fiber-optic probe coupled with an EEM system was used to acquire tissue AF EEMs using excitation wavelengths between 260 and 400 nm, and emission collection between 280 and 500 nm. A total of 152 AF EEM landscapes were acquired from 13 normal and 16 nasopharyngeal carcinoma (NPC) thawed ex vivo tissue samples from 23 patients. PARAFAC was introduced for curve resolution of individual AF EEM landscapes associated with the endogenous tissue constituents. The significant factors were further fed to a support vector machine (SVM) and cross-validated to construct diagnostic algorithms. Both the EEM intensity landscapes and the PARAFAC model revealed tryptophan, collagen, and elastin to be the three major endogenous fluorophores responsible for the AF signal from normal and NPC tissues. The EEM intensity distribution and PARAFAC factors suggest an increase of tryptophan and a decrease of collagen and elastin in NPC tissues compared to the normal. The classification results obtained from the PARAFAC-SVM modeling yielded a diagnostic accuracy of 94.7% (sensitivity of 95.0% (76/80); specificity of 94.4% (68/72)) for normal and NPC tissue differentiation. This study suggests that UV-excited AF EEM spectroscopy integrated with PARAFAC algorithms has the potential to provide clinical diagnostics of early onset and progression of NPC.
The Analyst 08/2011; 136(19):3896-903. · 4.23 Impact Factor
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ABSTRACT: 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.
Journal of Biomedical Optics 04/2011; 16(4):046014. · 3.16 Impact Factor
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ABSTRACT: The autofluorescence under ultraviolet excitation arising from normal squamous and columnar esophageal mucosa is investigated using multispectral microscopy. The results suggest that the autofluorescence signal arises from the superficial tissue layer due to the short penetration depth of the ultraviolet excitation. As a result, visualization of esophageal epithelial cells and their organization can be attained using wide-field autofluorescence microscopy. Our results show tryptophan to be the dominant source of emission under 266 nm excitation, while emission from NADH and collagen are dominant under 355 nm excitation. The analysis of multispectral microscopy images reveals that tryptophan offers the highest image contrast due to its non-uniform distribution in the sub-cellular matrix. This technique can simultaneously provide functional and structural imaging of the microstructure using only the intrinsic tissue fluorophores.
Optics Express 09/2010; 18(20):21074-82. · 3.59 Impact Factor
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ABSTRACT: Detection of esophageal disease in current clinical practice is limited to visualization of macroscopic epithelial morphology. In this work, we investigate high resolution autofluorescence imaging under ultra violet excitation to visualize microscopic epithelial changes related to disease progression using a bench top prototype microscope. The approach is based on the hypothesis that UV excitation light can only penetrate the superficial layer of cells resulting in autofluorescence images of the epithelial layer without using an additional image sectioning approach. The experiments were performed using ex vivo human esophagus biopsy specimens. The results indicate that cellular morphology information related to disease progression is attainable without tissue preparation.
Optics Express 08/2009; 17(15):12502-9. · 3.59 Impact Factor
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ABSTRACT: The signal intensity in near infrared autofluorescence and polarization sensitive light scattering imaging is explored as a function of tissue thickness using homogeneous porcine cardiac tissue samples as a model system. Eight images are recorded from each tissue sample including two autofluorescence images obtained under 408 nm and 633 nm excitation and six light scattering images acquired with alternating linear polarization orientations (parallel or perpendicular) under 700 nm, 850 nm, and 1000 nm linearly polarized illumination. The mean image intensity of each sample for each imaging method is plotted as a function of tissue thickness. The experimental results indicate a strong dependence of the detected signal on tissue thickness up to approximately 2 mm. Furthermore, the intensity of the spectral ratio images also exhibit thickness-dependent changes up to about 3 mm. The behavior of the light scattering experimental data was reproduced using a mathematical model based on a modified version of the random walk theory of photon migration.
Optics Express 01/2008; 15(25):16581-95. · 3.59 Impact Factor
