| Part 1 To explore the feasibility of EB-OCT in detecting the structural level of rabbit tracheaBackground and Objective:The normal trachea structures include mucosa layer,submucosa layer,smooth muscle layer and cartilage layer.At present,CT and endoscopic ultrasonography are used for the detection of trachea structure,and the images cannot accurately analyze the structure level of trachea wall.Optical coherence tomography imaging(optical coherence tomography,OCT)is a novel imaging technique with a principle similar to ultrasound,which constitutes two-dimensional and three-dimensional images by detecting the light and echo delay reflected back from biological tissues to obtain cross-sectional images of biological tissues,except that OCT uses light waves instead of sound waves and is applied in ophthalmology in the early stage,and then-it is gradually applied to the vascular system,digestive system,etc.,while there are few reports on the application of OCT in the respiratory system.Endo-bronchial optical coherence tomography(EB-OCT),which combines endoscopy and OCT,can enter the human body structure and detect the lumen wall and its surrounding tissues,In recent years,domestic EB-OCT has been successfully developed,but there is few clinical application data about respiratory diseases.In this study,we used domestic EB-OCT to detect the structural level of rabbit tracheal wall,compared its images with pathological images,explored the feasibility and image characteristics of EB-OCT in detecting the structural level of rabbit normal trachea,and provided a new means for EB-OCT in detecting the structural level of human tracheal wall in the futureMethods:We used EB-OCT to scan the same area of the trachea of 10 adult rabbits three times at a time.Then,these rabbits were sacrificed and a complete trachea specimen was collected.The specimens were fixed with formalin and stained with HE,the EB-OCT images were centered on the catheter,and the layers were inside-out labeled as O1(1-10),O2(1-10),O3(1-10),O4(1-10)....On(m),and measure its specific value;B1(1-10),B2(1-10),B3(1-10)and B4(1-10)were used to record the mucosal layer,submucosal layer,smooth muscle layer and cartilage layer of the histopathological images,and the thickness of each layer was measured by measuring software.We statistically analyzed the correlation between EB-OCT images and pathological images.Results:(1)EB-OCT shows the characteristics of rabbit tracheal structure images:hierarchical gray scale maps are presented according to the intensity of the signal.The tissue density presents different reflection intensities.The low signal appears black,the medium signal appears gray,and the high signal appears white.O1 is gray,O2 is white with strong reflection,O3 is grayish white,and O4 is black with weak reflection.(2)There is a linear trend between O1 and B1,and the linear regression equation is Y=5.5984+0.7629X(P<0.0001),with a positive linear correlation between the two.(3)There is a linear trend between O2 and B2,and the linear regression equation is Y=3.1050+0.9716X(P<0.0001),with a positive linear correlation between the two(4)There is a linear trend between O3 and B3,and the linear regression equation is Y=5.2229+0.9832x(P<0.0001),with a positive linear correlation between the two(5)There was a linear trend between O4 and B4,and the linear regression equation was Y=1.9805+0.9398X(P<0.0001),with a positive linear correlation between the two.(6)EB-OCT showed a high correlation between the thickness of all layers of the rabbit trachea and pathological findings,with correlation coefficients of 0.9923,0.9987,0.9998,and 0.9999,respectively.Conclusions:(1)EB-OCT images can clearly show the structure of the mucosal layer,submucosal layer,smooth muscle layer and cartilage layer of rabbit trachea.(2)The structure of each layer of rabbit tracheal wall reflected by EB-OCT images coincided with the actual histopathology.Part 2 To observe the formation of benign airway stenosis in injuredrabbits by EB-OCTBackground and objective:According to our previous study,we discovered that the main reason for the formation of post-traumatic stenosis was cartilage destruction,from which the type of stenosis is divided into mucosal destruction and cartilage destruction.At present,the main diagnostic methods of benign airway stenosis are CT and bronchoscopy,and the judgment of stenosis type depends on histopathological judgment.The existing treatment methods for benign airway stenosis are empirical treatment,such as cryotherapy,balloon dilatation,etc.The treatment options for different stenosis types should be different.If it is possible to accurately determine whether it is mucosal destruction or cartilage destruction,the problem of treatment strategy can be further solved.Optical coherence tomography(OCT)is a novel technique that uses interference imaging techniques and is able to provide cross-sectional maps of the microstructure under the surface of biological tissues.In the first part,through the comparative study of EB-OCT images and histopathological images of normal rabbit trachea,the OCT images of normal rabbit tracheal structure were obtained,and it was concluded that EB-OCT is a feasible method to detect the structural level of tracheal wall In this part,we established a rabbit model of tracheal stenosis by tracheal mucosal injury combined with cartilage injury,obtained the images and characteristics of benign airway stenosis observed by EB-OCT at different times in traumatized rabbits,and provided a new diagnostic method for further study of the formation mechanism and treatment of benign airway stenosis.Methods:The characteristics of bronchoscopic and EB-OCT images at 2 weeks,4 weeks,6 weeks and 8 weeks after operation in 12 rabbits with post-traumatic airway stenosis were observed and studied.At the same time,tracheal samples of 3 rabbits were obtained each time to collect histopathological images after HE staining;The EB-OCT image of the surgical site with the same direction of hours under tracheal mirror was taken as the matched image with the histopathological image,the thickness of the cartilage and non-cartilage layers in the matched part of the EB-OCT images was measured and labeled as C(O)and NC(O),and the thickness of the cartilage and non-cartilage layers in the histopathological images was measured using the measurement software and labeled as C(B)and NC(B).We statistically analyzed and compared the tracheal manifestations under bronchoscopy and the interaction between EB-OCT images and histopathological images in rabbits with traumatic airway stenosis.Results:(1)Granulation in the main tracheal lumen was observed in the trachea of traumatized rabbits two weeks after surgery,with significant stenosis;scar contracture and granulation hyperplasia coexisted at the four weeks after surgery,with further aggravation of stenosis;significant scar contracture was observed six weeks after surgery,with alleviation of stenosis;repaired scar contracture was observed eight weeks after surgery,with alleviation of stenosis(2)Pathological characteristics:2 weeks after operation,rabbit pathological tissue image showed submucosal granulation tissue hyperplasia,partial cilia hyperplasia and shedding,chondrocyte destruction;4 weeks after operation,pathological tissue image still showed a large amount of granulation tissue,partial fibrous connective tissue hyperplasia formed scar tissue,cilia shedding,cartilage destruction was obvious,some were accompanied by perichondrium destruction;6 weeks after operation,pathological tissue image showed fibrous connective tissue hyperplasia,scar tissue was the main,chondrocyte repair;8 weeks after operation,pathological tissue image showed obvious scar repair,loose connective tissue was close to normal,cartilage was further repaired.(3)EB-OCT features:Two weeks after surgery,the structure in the image was disordered,the mucosal layer and submucosal layer of the strong signal reflection band were widened,some of them were elevated inward,and the structure of the cartilage layer with low signal intensity was discontinuous.At 4 weeks after operation,the structure in the image was disordered,the strong and weak signals were mixed,some of them were elevated inward,and the hypointense cartilage layer was discontinuous.Six weeks after surgery,the strong signal band was clearly demarcated from the weak signal band,without bulging,the signal intensity of the strong signal band was enhanced,and the cartilage layer of the low signal band was partially discontinuous.At 8 weeks after operation,the image layer was clear,without bulge,the strong and weak signal bands were clearly demarcated,the white strong signal band signal was enhanced,and the cartilage layer of the weak signal band was continuous without destruction(4)There is a linear trend between NC(B)and NC(O),and the linear regression equation is Y=-9.4328+0.9935X,(P<0.0001),there was a linear positive correlation between the two;the correlation coefficient between the two was r=0.9999.There is a linear trend between C(B)and C(O),and the linear regression equation is Y=3.7498+0.9717X,(P<0.0001),there was a linear positive correlation between the two;the correlation coefficient between the two was r=0.9992.(5)There was no significant difference in the formation rate(100%)and type of stenosis(granulation hyperplasia,scar contracture)between EB-OCT and tracheal follow-up(P>0.05).There was no significant difference in the type of airway stenosis between EB-OCT and histopathology(mucosal destruction,cartilage destruction)(P>0.05)Conclusion:(1)Tracheal mucosal and cartilage injury is the key factor of benign airway stenosis in rabbits,and the main types of stenosis are granulation formation and scar contracture.(2)The dynamic acquired EB-OCT images of post-traumatic tracheal stenosis in rabbits were consistent with the histopathological images(3)EB-OCT can well distinguish the degree of tracheal mucosal destruction or/and cartilage destruction as well as the degree of destruction of both. |
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