Early diagnosis of ear disorders is difficult in part because patients do not seek out an otologist until they have significant hearing loss. Early detection could happen in the primary care provider’s office, however the sensitivity of an otoscopic examination by a primary care provider during an annual physical is very low. On the other hand, Optical Coherence Tomography (OCT) imaging of the tympanic membrane and middle ear can provide detailed volumetric images of the structure and function. These detailed images can form the basis for an approach for finding early signs of ear disease. Our hypothesis is that asymmetry between the ears could be used for early diagnosis. In order to test this, we need to understand the naturally occurring asymmetry in healthy volunteers. We have collected volumetric OCT images from 8 healthy subjects using a hand-held otoscopic OCT system. As part of a registration algorithm, we crop and down sample the data before finding the transformation matrix that registers the volumes. This matrix is then used to register the original volumes. Then the quantitative analysis of the symmetry between the left and right ears was applied through the similarity coefficient and overall, the left and right ears similarity of 8 healthy subjects has a mean of 0.7892, and a standard deviation of 0.0186. From a scientific perspective, this is the first quantitative measure of how symmetric the right and left ears are in humans. From a diagnostic perspective, this approach could provide a simple method to find early signs of ear disease.
Optical coherence tomography (OCT) has been shown to provide detailed images of the morphology and vibratory response in the living cochlea. As a part of the cochlea, the organ of Corti (OC) has a complex tissue structure including three rows of outer hair cells which act to amplify sound, supporting cells and one row of inner hair cells which transduce sound-induced vibrations into electrical signals. Unfortunately, OCT images of the OC have relatively low contrast, in spite of the fact that the microstructures have very different function and morphology. That fact has led us to explore alternative approaches to extracting contrast from these OCT images. In this paper, we propose a contrast-enhanced method based on spatial frequency to identify structures within the cochlea, including the OC. In total, 15 mice have been imaged with our customed OCT system and analyzed. A two-dimension spatial frequency analysis was performed over subregions of the images, using a sliding window. Then the power spectral density was fit to a 2-D Gaussian. Finally, we extracted several Gaussian fitting coefficients and constructed a coefficients map to enhance the visualization of the cochlea and identify structures within the OC. This method improves our ability to identify specific microstructures within the cochlea and ultimately map the functional vibratory response to these microstructures. Application of this approach can elucidate the micromechanical function of the cochlea.
Significance: Optical coherence tomography (OCT) has proven useful for detecting various oral maxillofacial abnormalities. To apply it to clinical applications including biopsy guidance and routine screening, a handheld imaging probe is indispensable. OCT probes reported for oral maxillofacial imaging were either based on a bulky galvanometric mirror pair (not compact or long enough) or a distal-end microelectromechanical systems (MEMS) scanner (raised safety concerns), or adapted from fiber-optic catheters (ill-suited for oral cavity geometry).
Aim: To develop a handheld probe featuring great compactness and excellent maneuverability for oral maxillofacial tissue imaging.
Approach: A dual-axis MEMS scanner was deployed at the proximal end of the probe and the scanned beam was relayed to the distal end through a 4f configuration. Such design provides both a perfect dual-axis telecentric scan and excellent compactness.
Results: A handheld probe with a rigid part 70 mm in length and 7 mm in diameter and weighing 25 g in total was demonstrated through both ex vivo and in vivo experiments, including structural visualization of various oral maxillofacial tissues and monitoring the recovery process of an oral mucosa canker sore.
Conclusions: The proposed probe exhibits excellent maneuverability and imaging performance showing great potential in clinical applications.
Lymphatic metastasis is a main pathway of dissemination of malignancies. The diagnosis of metastasis in lymph nodes can help stage cancer or help the surgeons make intraoperative decisions. In addition, lymph nodes are more easily confused with other neck tissues during thyroid surgery. Therefore, identification of lymph nodes is very important. Up to now, the gold standard for identification of metastatic lymph nodes is still histological examination, which can only be performed ex vivo and needs a long time. Optical coherence tomography (OCT) is a non-invasive, high-resolution imaging technology that is capable of detecting microstructures in bio-tissues in real time. In this study, we demonstrated a method to identify metastatic lymph nodes automatically by intraoperative OCT imaging. With a home-made swept source OCT system, we obtained OCT images of different resected neck tissues, including lymph nodes with and without metastasis, thyroid, parathyroid, fat and muscle, from 28 patients undertaking thyroidectomy. The automatic identification algorithm was based on texture analysis and back-propagation artificial neural network (BP-ANN). 66 texture features of OCT images were extracted and 14 were selected and used for automatic identification experiments. The trained BP-ANN has an excellent performance in identifying OCT images of lymph nodes with the sensitivity of 98.9 % and specificity of 98.8 %. The accuracy of lymphatic metastasis diagnosis is 90.1 %.
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