Abstract
Development of effective rescue countermeasures for toxic inhalational industrial chemicals, such as methyl isocyanate (MIC), has been an emerging interest. Nonetheless, current methods for studying toxin-induced airway injuries are limited by cost, labor time, or accuracy, and only provide indirect or localized information. Optical Coherence Tomography (OCT) endoscopic probes have previously been used to visualize the 3-D airway structure. However, gathering such information in small animal models, such as rat airways after toxic gas exposure, remains a challenge due to the required probe size necessary for accessing the small, narrow, and partially obstructed tracheas. In this study, we have designed a 0.4 mm miniature endoscopic probe and investigated the structural changes in rat trachea after MIC inhalation. An automated 3D segmentation algorithm was implemented so that anatomical changes, such as tracheal lumen volume and cross-sectional areas, could be quantified. The tracheal region of rats exposed to MIC by inhalation showed significant airway narrowing, especially within the upper trachea, as a result of epithelial detachment and extravascular coagulation within the airway. This imaging and automated reconstruction technique is capable of rapid and minimally-invasive identification of airway obstruction. This method can be applied to large-scale quantitative analysis of in vivo animal models.
Highlights
The development of effective countermeasures to inhalation poisoning by industrial chemicals has been of great interest for several decades
Airways of rats exposed in an methyl isocyanate (MIC) inhalation model were first visualized using an all-fiber miniature Optical Coherence Tomography (OCT) probe that was optimized for imaging within rat airways
The outer diameter of the fabricated probe was 0.4 mm, which was much smaller than the previously designed 1.2 mm endoscopic probe used for humans[16]
Summary
The development of effective countermeasures to inhalation poisoning by industrial chemicals has been of great interest for several decades. To translate our studies into the airways of rodent models requires a significantly more compact endoscopic probe than previous designs since the diameter of a typical rat trachea is about 6 times smaller than a human’s Another limitation in previous studies was the manual tracing utilized to reconstruct the 3D structure of the airway from OCT images. An automatic segmentation method based on edge detection and graph theory has been recently developed to delineate and quantify the interior airway lining[20,21] Those studies have been mostly limited to distinguishing tissue structure, such as thickness in 2D OCT images. We optimized the design of a previously developed all fiber optic endoscopic probe for use within rat trachea and applied an automated segmentation algorithm on OCT images to generate accurate 3D reconstructions. This paper details the fabrication process of an all-fiber probe, method of automated segmentation, and analytic results in an MIC-exposed rat model
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