Optical coherence microscopy (OCM) combines coherence gating, high numerical aperture optics, and a fiber-core pinhole to provide high axial and lateral resolution with relatively large depth of imaging. We present a handheld rigid OCM endoscope designed for small animal surgical imaging, with a 6-mm diam tip, 1-mm scan width, and 1-mm imaging depth. X-Y scanning is performed distally with mirrors mounted to micro galvonometer scanners incorporated into the endoscope handle. The endoscope optical design consists of scanning doublets, an afocal Hopkins relay lens system, a 0.4 numerical aperture water immersion objective, and a cover glass. This endoscope can resolve laterally a 1.4-μm line pair feature and has an axial resolution (full width half maximum) of 5.4 μm. Images taken with this endoscope of fresh ex-vivo mouse ovaries show structural features, such as corpus luteum, primary follicles, growing follicles, and fallopian tubes. This rigid handheld OCM endoscope can be useful for a variety of minimally invasive and surgical imaging applications.
Optical Coherence Microscopy (OCM) combines coherence gating, high numerical aperture optics, and a fiber core pinhole to provide high axial and lateral resolution with relatively large depth of imaging. We present a handheld rigid OCM endoscope with a 6 mm diameter tip, 1 mm scan width, and 1 mm imaging depth. This probe will allow noninvasive imaging of fine structural detail in vivo.
X-Y scanning is performed distally with mirrors mounted to micro galvonometer scanners incorporated into the endoscope handle. Two scanning doublet lenses relay the stop from the galvonometers to the afocal relay stop. The endoscope optical design consists of an afocal Hopkins relay lens system and a 0.4 NA objective. To allow focusing at
various depths in the tissue, the endoscope housing is designed in two pieces screwed together with a fine pitch threads.
A small rotation of the outer housing moves the lenses proximal and distal relative to the window, causing the focal
location in the tissue to change. The space between the final objective lens and the window is filled with distilled water
to avoid misalignment of the focus and coherence gate.
A knife edge test was performed and the line spread function FWHM was measured to be 2.25 μm. The MTF has at least 0.3 contrast at a 5 μm line pair. This rigid handheld OCM endoscope will be useful for application ranging from minimally invasive surgical imaging to assessing dysplasia and sun damage in skin.
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.
Objective: To automatically segment cell nuclei in histology images of bladder and skin tissue for karyometric analysis.
Materials/Methods: The four main steps in the program were as follows: 1) median filtering and thresholding, 2)
segmentation, 3) categorizing, and 4) cusp correction. This robust segmentation technique used properties of the image
histogram to optimally select a threshold and create closed four-way chain code nuclei segmentations. Each cell nucleus
segmentation was treated as an individual object with properties of segmentation quality. A segmentation was placed in
one of the following three categories based on its properties: throw away, salvageable, or good. Erosion/dilation and rethresholding
were performed on salvageable nuclei to correct cusps.
Results: Ten bladder histology images were segmented both by hand and using this automatic segmention algorithm.
The automatic segmentation resulted in a sensitivity of 76.4%. The average difference between hand and automatic
segmentations over 42 nuclei, calculated for each of the 95 features used in karyometric analysis, ranged between 0 and
48.3%, with an average of 2.8%. The same procedure was performed on 10 skin histology images with a sensitivity of
83.0%. Average differences over 44 nuclei ranged between 0 and 200%, with an average of 10.0%.
Conclusion: The close agreement in karyometric features with hand segmentation shows that automated segmentation
can be used for analysis of bladder and skin histology images. Average differences between hand and automatic
segmentations were smaller in bladder histology images because these images contained less contrast, and therefore the
range of the karyometric feature values was smaller.