Point-of-care depth resolved 3D imaging of the tympanic membrane and middle ear with OCT, combined with quantitative image analysis, could improve the diagnosis and management of patients in the clinical setting. We imaged the TMs and MEs of 55 patients in a neurotology clinic, using a custom-built hand-held OCT (HHOCT) device. Patients with a diagnosis of TM retraction pockets, perforations, cholesteatomas, and postoperative states were included in this study. Healthy volunteers were also imaged to provide a baseline for quantitative metrics. Images were post processed to perform segmentation of the TM and create thickness maps of the TM, derive mean TM thickness values, and conduct ear symmetry analysis. The normal mean TM thickness was found to be significantly different from every other condition explored. Ear symmetry of healthy subjects was found to be 80% between left and right ears. Quantitative metrics derived from OCT images can be used to characterize TM pathologies and potentially aid in diagnosis and management.
SignificancePathologies within the tympanic membrane (TM) and middle ear (ME) can lead to hearing loss. Imaging tools available in the hearing clinic for diagnosis and management are limited to visual inspection using the classic otoscope. The otoscopic view is limited to the surface of the TM, especially in diseased ears where the TM is opaque. An integrated optical coherence tomography (OCT) otoscope can provide images of the interior of the TM and ME space as well as an otoscope image. This enables the clinicians to correlate the standard otoscopic view with OCT and then use the new information to improve the diagnostic accuracy and management.AimWe aim to develop an OCT otoscope that can easily be used in the hearing clinic and demonstrate the system in the hearing clinic, identifying relevant image features of various pathologies not apparent in the standard otoscopic view.ApproachWe developed a portable OCT otoscope device featuring an improved field of view and form-factor that can be operated solely by the clinician using an integrated foot pedal to control image acquisition. The device was used to image patients at a hearing clinic.ResultsThe field of view of the imaging system was improved to a 7.4 mm diameter, with lateral and axial resolutions of 38 μm and 33.4 μm, respectively. We developed algorithms to resample the images in Cartesian coordinates after collection in spherical polar coordinates and correct the image aberration. We imaged over 100 patients in the hearing clinic at USC Keck Hospital. Here, we identify some of the pathological features evident in the OCT images and highlight cases in which the OCT image provided clinically relevant information that was not available from traditional otoscopic imaging.ConclusionsThe developed OCT otoscope can readily fit into the hearing clinic workflow and provide new relevant information for diagnosing and managing TM and ME disease.
We have been investigating Optical Coherence Tomography (OCT) as a tool to measure the tympanic membrane and middle ear morphology and vibrational response. The hand-held OCT ostoscope system, based on a 1.3 µm swept laser, is integrated into an endoscopy cart. It has an ~ 8 mm diameter field of view, 38 µm lateral resolution, 35 µm axial resolution, A-line rate of 200 kHz, and subnanometer sensitivity to vibration within the tympanic membrane and middle ear. The system has been used in the clinic at USC Keck Medical Center to image over 100 patients and healthy volunteers. Total imaging time is ~2 minutes, which allows it to easily fit into the clinic workflow, while providing high-resolution images and vibrometric assessment of the tympanic membrane and middle ear. The functional and morphological features visible within these image sets that allow us to readily differentiate among pathologies, will be discussed.
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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