Polarimetric glucose sensing is a promising method for noninvasive estimation of blood glucose concentration.
Published methods of polarimetric glucose sensing generally rely on measuring the rotation of light as it traverses
the aqueous humor of the eye. In this article, an interferometer is described that can detect polarization changes
due to glucose without the use of polarization control or polarization analyzing elements. Without polarizers,
this system is sensitive to optical activity, inherent to glucose, but minimally sensitive to linear retardance,
inherent to the cornea. The underlying principle of the system was experimentally verified using spectral domain
optical coherence tomography. A detection scheme involving amplitude modulation was simulated, demonstrating
sensitivity to clinically relevant glucose concentrations and an acceptable error due to time varying linear
birefringence of the cornea using Clarke Error Grid Analysis.
A new focused OCT-LIF endoscope has been constructed for high resolution imaging between 325 nm and 1300 nm.
This endoscope is 2 mm in diameter for non-destructive imaging in vivo. A reflective design ball lens is employed that
eliminates the difficulty of operating achromatically over a large range, while taking advantage of TIR at two faces and
coating a third mirror face internally to focus the beams downwards. It is a 1:1 imaging system that obtains a theoretical
diffraction-limited resolution for both the OCT (800-1300 nm) and LIF (greater than 325 nm) channels.
Ovarian cancer is the fourth leading cause of cancer-related death among women. If diagnosed at early stages, 5-year survival rate is 94%, but drops to 68% for regional disease and 29% for distant metastasis; only 19% of cases are diagnosed at early, localized stages. Optical coherence tomography is a recently emerging non-destructive imaging technology, achieving high axial resolutions (10-20 µm) at imaging depths up to 2 mm. Previously, we studied OCT in normal and diseased human ovary ex vivo. Changes in collagen were suggested with several images that correlated with changes in collagen seen in malignancy. Areas of necrosis and blood vessels were also visualized using OCT, indicative of an underlying tissue abnormality. We recently developed a custom side-firing laparoscopic OCT (LOCT) probe fabricated for in vivo imaging. The LOCT probe, consisting of a 38 mm diameter handpiece terminated in a 280 mm long, 4.6 mm diameter tip for insertion into the laparoscopic trocar, is capable of obtaining up to 9.5 mm image lengths at 10 µm axial resolution. In this pilot study, we utilize the LOCT probe to image one or both ovaries of 17 patients undergoing laparotomy or transabdominal endoscopy and oophorectomy to determine if OCT is capable of differentiating normal and neoplastic ovary. We have laparoscopically imaged the ovaries of seventeen patients with no known complications. Initial data evaluation reveals qualitative distinguishability between the features of undiseased post-menopausal ovary and the cystic, non-homogenous appearance of neoplastic ovary such as serous cystadenoma and endometroid adenocarcinoma.
Ovarian cancer is the fourth leading cause of cancer-related death among women in the United States. If diagnosed at an
early stage, the 5-year survival rate is 94%, but drops to 68% for regional disease and 29% for distant metastasis; only
19% of all cases are diagnosed at the early, localized stage. Optical coherence tomography is a recently emerging non-destructive
imaging technology, achieving high axial resolutions (10-20 microns) at imaging depths up to 2 mm.
Previously, we studied OCT imaging in normal and diseased human ovary ex vivo to determine the features OCT is
capable of resolving. Changes in collagen were suggested with several of the images that correlated with changes in
collagen seen in malignancy. Areas of necrosis and blood vessels were also visualized using OCT, indicative of an
underlying tissue abnormality. We recently developed a custom side-firing laparoscopic OCT (LOCT) probe fabricated
specifically for in vivo laparoscopic imaging. The LOCT probe consists of a 38 mm diameter handpiece terminated in an
280 mm long, 4.6 mm diameter tip for insertion into the laparoscopic trocar and is capable of obtaining up to 9.5 mm
image lengths at 10 micron axial resolution. In this study, we utilize the LOCT probe to image one or both ovaries of 20
patients undergoing laparotomy or transabdominal endoscopy and oophorectomy to determine if OCT is capable of
identifying and/or differentiating normal and neoplastic ovary. To date, we have laparoscopically imaged the ovaries of
ten patients successfully with no known complications.
An ideal vascular stent design promotes a thin anti-thrombogenic cellular lining while avoiding restenosis. To assess the utility of their designs, stent manufactures often use destructive techniques such as scanning electron microscopy to measure the percentage of the stent covered with a cellular lining. In this study, we use a custom-built longitudinal/rotational scanning endoscope and determine the ability of optical coherence tomography (OCT) to quantify the percent cellular coverage of stented tissue engineered blood vessel mimics. Stents were deployed within twelve mimics after 14-days of development in bioreactors. OCT images were acquired within the bioreactor at several time points after the stent deployment. At 20-days post deployment, the mimics were fixed and imaged volumetrically with OCT. Matlab software was developed to automatically calculate the percent cellular coverage from the OCT images. Algorithm results were compared to similar measurements performed with bis-benzimide (BBI) fluorescence imaging and manually calculated percent coverage from three different observers of the OCT images. Progressive accumulation of cellular material on the stents could be visualized with OCT. For the volumetric images, the algorithm calculated percent cellular coverages ranging from 11 to 76%. Good agreement was found between the OCT-based measurements and the other techniques. On average, the algorithm differed less than 5% from the manual percent coverage calculations. OCT together with automated software can provide an accurate, non-destructive measurement of the percent cellular coverage of vascular stents.
Optical coherence tomography (OCT) is an imaging modality that enables assessment of tissue structural characteristics. Studies have indicated that OCT is a useful method to assess both blood vessel morphology and the response of a vessel to a deployed stent. We evaluated the ability of OCT to visualize the cellular lining of a tissue-engineered blood vessel mimic (BVM) and the response of this lining to a bare metal stent. We develop a side-firing endoscope that obtains intraluminal, longitudinal scans within the sterile bioreactor environment, enabling time-serial assessment. Seventeen BVMs are imaged with the endoscopic OCT system. The BVMs are then evaluated via fluorescence microscopy and/or standard histologic techniques. We determine that (1) the OCT endoscope can be repeatedly inserted without visible damage to the BVM cellular lining, (2) OCT provides a precise measure of cellular lining thickness with good correlation to measurements obtained from histological sections, and (3) OCT is capable of monitoring the accumulation of cellular material in response to a metallic stent. Our studies indicate that OCT is a useful technique for monitoring the BVM cellular lining, and that OCT may facilitate the use of BVMs for early stage device assessment.
Optical Coherence Microscopy (OCM) enables the acquisition of high resolution, en face images. Most current OCM systems are based on slow analog or high speed digital demodulation schemes. In this paper we demonstrate a low-cost, high speed analog fringe generation and demodulation method. A high power operational amplifier drives a mirrored piezoelectric stack mounted in the reference arm of the interferometer. The drive signal is synchronized with the demodulation frequency of two analog lock-in amplifiers, which extract the first and second harmonic power of the coherence fringes. Tenth order Bessel low-pass filters (LPFs) allow fast system response and reduce carrier frequency noise. Four outputs (X and Y components of first and second harmonic) are acquired with a low-cost data acquisition board and combined to eliminate the slow phase drift in the interferometer. C# software processes and displays the image, and performs automatic interferometer pathlength matching and adjustment. We present images of Arabidopsis leaf in situ, sections of carrot, and ex vivo rat ovary. Excellent image quality is achieved at acquisition speeds up to 40,000 samples/second.