With early detection, 5-year survival rates for ovarian cancer exceed 90%, yet no effective early screening method exists. Emerging consensus suggests over 50% of the most lethal form of the disease originates in the fallopian tube. Twenty-eight women undergoing oophorectomy or debulking surgery provided informed consent for the use of surgical discard tissue samples for multispectral fluorescence imaging. Using multiple ultraviolet and visible excitation wavelengths and emissions bands, 12 fluorescence and 6 reflectance images of 47 ovarian and 31 fallopian tube tissue samples were recorded. After imaging, each sample was fixed, sectioned, and stained for pathological evaluation. Univariate logistic regression showed cancerous tissue samples had significantly lower intensity than noncancerous tissue for 17 image types. The predictive power of multiple image types was evaluated using multivariate logistic regression (MLR) and quadratic discriminant analysis (QDA). Two MLR models each using two image types had receiver operating characteristic curves with area under the curve exceeding 0.9. QDA determined 56 image type combinations with perfect resubstituting using as few as five image types. Adaption of the system for future in vivo fallopian tube and ovary endoscopic imaging is possible, which may enable sensitive detection of ovarian cancer with no exogenous contrast agents.
Aberrant crypt foci (ACF) are abnormal epithelial lesions that precede development of colonic polyps. As the earliest morphological change in the development of colorectal cancer, ACF is a highly studied phenomenon. The most common method of imaging ACF is chromoendoscopy using methylene blue as a contrast agent. Narrow- band imaging is a contrast-agent-free modality for imaging the colonic crypts. Optical coherence tomography (OCT) is an attractive alternative to chromoendoscopy and narrow-band imaging because it can resolve the crypt structure at sufficiently high sampling while simultaneously providing depth-resolved data. We imaged in vivo the distal 15 mm of colon in the azoxymethane (AOM) mouse model of colorectal cancer using a commercial swept-source OCT system and a miniature endoscope designed and built in-house. We present en face images of the colonic crypts and demonstrate that different patterns in healthy and adenoma tissue can be seen. These patterns correspond to those reported in the literature. We have previously demonstrated early detection of colon adenoma using OCT by detecting minute thickening of the mucosa. By combining mucosal thickness measurement with imaging of the crypt structure, OCT can be used to correlate ACF and adenoma development in space and time. These results suggest that OCT may be a superior imaging modality for studying the connection between ACF and colorectal cancer.
Colorectal cancer remains the second deadliest cancer in the United States, despite the high sensitivity and specificity of colonoscopy and sigmoidoscopy. While these standard imaging procedures can accurately detect medium and large polyps, some studies have shown miss rates up to 25% for polyps less than 5 mm in diameter. An imaging modality capable of detecting small lesions could potentially improve patient outcomes.
Optical coherence tomography (OCT) has been shown to be a powerful imaging modality for adenoma detection in a mouse model of colorectal cancer. While previous work has focused on analyzing the structural OCT images based on thickening of the mucosa and changes in light attenuation in depth, imaging the microvasculature of the colon may enable earlier detection of polyps. The structure and function of vessels grown to support tumor growth are markedly different from healthy vessels. Doppler OCT is capable of imaging microvessels in vivo.
We developed a method of processing raw fringe data from a commercial swept-source OCT system using a lab-built miniature endoscope to extract microvessels. This method can be used to measure vessel count and density and to measure flow velocities. This may improve early detection and aid in the development of new chemopreventive and chemotherapeutic drugs. We present, to the best of our knowledge, the first endoscopic Doppler OCT images of in vivo mouse colon.
Optical coherence tomography/laser induced fluorescence (OCT/LIF) dual-modality imaging allows for minimally invasive, nondestructive endoscopic visualization of colorectal cancer in mice. This technology enables simultaneous longitudinal tracking of morphological (OCT) and biochemical (fluorescence) changes as colorectal cancer develops, compared to current methods of colorectal cancer screening in humans that rely on morphological changes alone. We have shown that QDot655 targeted to vascular endothelial growth factor receptor 2 (QD655-VEGFR2) can be applied to the colon of carcinogen-treated mice and provides significantly increased contrast between the diseased and undiseased tissue with high sensitivity and specificity ex vivo. QD655-VEGFR2 was used in a longitudinal in vivo study to investigate the ability to correlate fluorescence signal to tumor development. QD655-VEGFR2 was applied to the colon of azoxymethane (AOM-) or saline-treated control mice in vivo via lavage. OCT/LIF images of the distal colon were taken at five consecutive time points every three weeks after the final AOM injection. Difficulties in fully flushing unbound contrast agent from the colon led to variable background signal; however, a spatial correlation was found between tumors identified in OCT images, and high fluorescence intensity of the QD655 signal, demonstrating the ability to detect VEGFR2 expressing tumors in vivo.
With early detection, five year survival rates for ovarian cancer are over 90%, yet no effective early screening method
exists. Emerging consensus suggests that perhaps over 50% of the most lethal form of the disease, high grade serous
ovarian cancer, originates in the Fallopian tube. Cancer changes molecular concentrations of various endogenous
fluorophores. Using specific excitation wavelengths and emissions bands on a Multispectral Fluorescence Imaging (MFI)
system, spatial and spectral data over a wide field of view can be collected from endogenous fluorophores. Wavelength
specific reflectance images provide additional information to normalize for tissue geometry and blood absorption.
Ratiometric combination of the images may create high contrast between neighboring normal and abnormal tissue.
Twenty-six women undergoing oophorectomy or debulking surgery consented the use of surgical discard tissue samples
for MFI imaging. Forty-nine pieces of ovarian tissue and thirty-two pieces of Fallopian tube tissue were collected and
imaged with excitation wavelengths between 280 nm and 550 nm. After imaging, each tissue sample was fixed, sectioned
and HE stained for pathological evaluation. Comparison of mean intensity values between normal, benign, and cancerous
tissue demonstrate a general trend of increased fluorescence of benign tissue and decreased fluorescence of cancerous
tissue when compared to normal tissue. The predictive capabilities of the mean intensity measurements are tested using
multinomial logistic regression and quadratic discriminant analysis. Adaption of the system for in vivo Fallopian tube and
ovary endoscopic imaging is possible and is briefly described.
Ovarian cancer is particularly deadly because it is usually diagnosed after it has metastasized. We have previously identified features of ovarian cancer using optical coherence tomography (OCT) and second-harmonic generation (SHG) microscopy (targeting collagen). OCT provides an image of the ovarian microstructure, while SHG provides a high-resolution map of collagen fiber bundle arrangement. Here, we investigated the diagnostic potential of dual-modality OCT and SHG imaging. We conducted a fully crossed, multireader, multicase study using seven human observers. Each observer classified 44 ex vivo mouse ovaries (16 normal and 28 abnormal) as normal or abnormal from OCT, SHG, and simultaneously viewed, coregistered OCT and SHG images and provided a confidence rating on a six-point scale. We determined the average receiver operating characteristic (ROC) curves, area under the ROC curves (AUC), and other quantitative figures of merit. The results show that OCT has diagnostic potential with an average AUC of 0.91±0.06. The average AUC for SHG was less promising at 0.71±0.13. The average AUC for simultaneous OCT and SHG was not significantly different from OCT alone, possibly due to the limited SHG field of view. The high performance of OCT and coregistered OCT and SHG warrants further investigation.
Ovarian cancer is particularly deadly because it is usually diagnosed after it has begun to spread. Transvaginal
sonography (TVS) is the most common imaging screening technique. However, routine use of TVS has not reduced
ovarian cancer mortality. The superior resolution of optical imaging techniques may make them attractive alternatives to
TVS. We have previously identified features of ovarian cancer using optical coherence tomography (OCT) and secondharmonic
generation (SHG) microscopy (with collagen as the targeted fluorophore). OCT provides a gross anatomical
image of the ovary while SHG provides a closer look at a particular region. Knowing these anatomical features, we
sought to investigate the diagnostic potential of OCT and SHG.
We conducted a fully crossed, multi-reader, multi-case study using seven human observers. Each observer classified 44
ex vivo mouse ovaries as normal or abnormal from OCT, SHG, and simultaneous, co-registered OCT and SHG images
and provided a confidence rating on a three-point ordinal scale. We determined the average receiver operating
characteristic (ROC) curves, area under the ROC curves (AUC), and other quantitative figures of merit. The results show
that OCT has diagnostic potential with an average AUC of 0.91 ± 0.03. The average AUC for SHG was less promising at
0.71 ± 0.06. Interestingly, the average AUC for simultaneous, co-registered OCT and SHG was not significantly
different from OCT alone. This suggests that collagen may not be a useful fluorophore for ovarian cancer screening. The
high performance of OCT warrants further investigation.
KEYWORDS: Endoscopes, Optical coherence tomography, Colon, In vivo imaging, 3D image processing, Endoscopy, Tissues, Imaging systems, Colorectal cancer, 3D scanning
We have previously developed side-viewing endoscopic OCT systems to detect colorectal cancer in the murine model, which longitudinally scans the mouse colon at 8-16 discrete angular positions. This small number of angles is chosen to keep imaging time and the amount of data to analyze reasonable, but this azimuthal undersampling of the tissue may result in missed or incorrectly characterized adenomas. A need exists for a spiral-scanning OCT endoscope capable of generating 3D, in vivo OCT data sets that satisfy the Nyquist criterion for adequate sampling of the tissue. Our new endoscopic system replaces the sample arm optics of a commercial OCT system with a spiral-scanning, gradient-index lens-based endoscope. The endoscope provides unit magnification at a working distance capable of producing a focal depth of 280 μm in tissue. The working distance accounts for a 41° rod prism that reflects the beam through the endoscopic window into the tissue while minimizing back reflection. A swept-source laser with a central wavelength of 1040 nm and spectral bandwidth of 80 nm provides an axial resolution of 12 μm in air and 9 μm in water. The endoscope has a theoretical diffraction-limited lateral resolution of 5.85 μm. We present fully sampled, 3D, in vivo images of the mouse colon.
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