Significance: While spectral-domain optical coherence tomography (SD-OCT) is a preferred form of OCT imaging, sensitivity roll-off limits its applicability for certain biomedical imaging applications.
Aim: The aim of this work is to extend the imaging range of conventional SD-OCT systems for imaging large luminal organs such as the gastrointestinal tract.
Approach: We present an SD-OCT system operating at a center wavelength of 1300 nm that uses two delayed reference arms to reduce sensitivity roll-off and an optical switch and a fiber optic delay line to ensure that the interference spectra are acquired from the same sample time window.
Result: The proposed system was used to image swine colon ex vivo and duodenum in vivo, demonstrating improved image quality due to a ∼14 dB increase in sensitivity at the edges of the ranging depth.
Conclusion: The proposed system requires modest hardware implementation and is compatible with catheter-based endoscopic helical scanning with enhanced sensitivity for the samples at a distance of ∼6 mm from the zero delay point.
Upper endoscopy is a standard technique for imaging, sampling, and treating gastrointestinal tissue. Endoscopy is frequently requiring the subjects who undergo the procedure be consciously sedated. Sedation necessitates that the endoscopy procedure be conducted in a specialized setting to mitigate complications should they arise. Endoscopy is further problematic for infants and young children (aged 0-24 months) who sometimes need to be anesthetized. These issues motivate alternative methods for upper gastrointestinal tract visualization and biopsy that do not require conscious sedation/anesthesia. To address this need, we have developed a double lumen 6.5 Fr transnasal introduction catheter (TNIC). During transnasal insertion, real-time OCT imaging provides confirmation of the anatomical location of the device. Once in the stomach, a safe and high-density liquid metal fills a balloon at the distal tip of the TNIC, allowing it to passively transit through stomach into the small intestine. Once properly positioned, OCT-guided instruments for imaging and biopsy can be inserted through main lumen of the TNIC, performing many of the functions of conventional endoscopy and advanced endomicroscopy. To test the feasibility of the TNIC, we conducted a clinical study using the first version of the device in 4 unsedated normal volunteers. Results showed detailed OCT endomicroscopy images of the esophagi and duodena. These results suggest that TNIC may be an effective, less invasive method for the diagnosis of upper GI tract conditions.
Environmental enteric dysfunction (EED) is a poorly understood condition of the small intestine prevalent in low and middle income countries. This disease is believed to cause nutrient malabsorption and poor oral vaccine uptake, resulting in arrested neurological development and growth stunting in children that persists as they grow into adulthood. Optical coherence tomography (OCT) imaging of the small intestine can potentially capture some of the microstructural changes, such as villous blunting, in the small gut that accompany EED, and hence could potentially improve the understanding of EED and help in determining and monitoring the effectiveness of EED interventions. Notably, EED must be studied and diagnosed in infants, aged 0-24 months as this is the only window in which interventional strategies can reverse the disease. In order to address this need, we propose a trans-nasal OCT imaging technique for imaging the small intestine that may be suitable for low-resource settings owing to its simplicity, ease of administration, and implementation in unsedated infants. To demonstrate the potential of transnasal OCT intestinal imaging, we have created a 10 Fr transnasal OCT imaging probe and have submitted an IRB application for a first-in-human study using this probe to image the adult small intestine. We anticipate that the results from this pilot study will justify the development of a transnasal OCT intestinal imaging device for infants.
Environmental enteric dysfunction (EED) is a poorly understood disease of the small intestine that causes nutrient malabsorption in children, predominantly from low and middle income countries. The clinical importance of EED is neurological and growth stunting that remains as the child grows into adulthood. Tethered capsule endomicroscopy (TCE) has the potential to improve the understanding of EED and could be used to determine the effectiveness of EED interventions. TCE in the adult esophagus and the duodenum has been demonstrated for Barrett`s esophagus and celiac disease diagnosis, respectively. While adult subjects can independently swallow these capsules, it is likely that infants will not, and, as a result, new strategies for introducing these devices in young children aged 0.5-2 years need to be investigated. Our first approach will be to introduce the TCE devices in infants under the aid of endoscopic guidance. To determine the most effective method, we have tested endoscopic approaches for introducing TCE devices into the small intestine of living swine. These methods will be compared and contrasted to discuss the most effective means for endoscopic tethered capsule introduction into the small intestine.
A reflection type white light diffraction phase microscope for full field surface profiling of opaque samples is proposed. The system can extract surface profile from one recorded interferogram without any mechanical movement and the use of white light makes it free from speckle noise. We validated the performance of our system by measuring a known step sample and a high-quality plane sample. The step height of the step sample is found to be 88.5 nm with a standard deviation of 1.4 nm, and the surface peak to valley value of the plane sample is found to be 28.6 nm with a standard deviation of 3 nm.
KEYWORDS: Optical coherence tomography, Brain, Refractive index, Neuroimaging, In vivo imaging, Crystals, 3D modeling, Systems modeling, Cornea, Imaging systems
Zebrafish (Danio rerio), a vertebrate, is a good model system in medical research to understand a variety of
human biological processes. These studies often require measurements of the morphological and physiological
parameters of Zebrafish. Therefore, development of noninvasive imaging techniques for this purpose is of considerable
interest. In this article, we present a brief overview of the use of OCT for noninvasive in-vivo imaging of adult Zebrafish.
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