Porcine Colon Research Articles

Macro-Scale Tread Patterns for Traction in the Intestine.

Tread patterns are widely used to increase traction on different substrates, with the tread scale, geometry and material being tailored to the application. This work explores the efficacy of using macro-scale tread patterns for a medical application involving a colon substrate - renowned for its low friction characteristics. Current literature was first summarized before an experimental approach was used, based on a custom test rig with ex vivo porcine colon, to assess different macro-scale tread patterns. Performance was based on increasing traction while avoiding significant trauma. Repeated testing (n = 16) was used to obtain robust results. A macro-scale tread pattern can increase the traction coefficient significantly, with a static traction coefficient of 0.74 ± 0.22 and a dynamic traction coefficient of 0.35 ± 0.04 compared to a smooth (on the macro-scale) Control (0.132 ± 0.055 and 0.054 ± 0.015, respectively). Decreasing the scale and spacing between the tread features reduced apparent trauma but also reduced the traction coefficient. Significant traction can be achieved on colon tissue using a macro-scale tread but a compromise between traction (large feature sizes) and trauma (small feature sizes) may have to be made. This work provides greater insight into the complex frictional mechanisms of the intestine and gives suggestions for developing functional tread surfaces for a wide range of clinical applications.

Zinc prevents intestinal epithelial barrier dysfunction induced by alpha-hemolysin-producing Escherichia coli 536 infection in porcine colon

Zinc treatment is beneficial for infectious diarrhea or colitis. This study aims to characterize the pathomechanisms of the epithelial barrier dysfunction caused by alpha-hemolysin (HlyA)-expressing Escherichia coli in the colon mucosa and the mitigating effects of zinc ions.We performed Ussing chamber experiments on porcine colon epithelium and infected the tissues with HlyA-producing E. coli. Colon mucosa from piglets was obtained from a feeding trial with defined normal or high dose zinc feeding (pre-conditioning). Additional to the zinc feeding, zinc was added to the luminal compartment of the Ussing chamber. Transepithelial electrical resistance (TER) was measured during the infection of the living tissue and subsequently the tissues were immuno-stained for confocal microscopy.Zinc applied to the luminal compartment was effective in preventing from E. coli-induced epithelial barrier dysfunction in Ussing chamber experiments. In contrast, zinc pre-conditioning of colon mucosae when zinc ions were missing subsequently in the luminal compartment was not sufficient to prevent epithelial barrier impairment during E. coli infection. The pathological changes caused by E. coli HlyA were alterations of tight junction proteins claudin-4 and claudin-5, focal leak formation, and cell exfoliation which reflected the paracellular barrier defect measured by a reduced TER. In microscopic analysis of luminal zinc-treated mucosae these changes were absent.In conclusion, continuous presence of unbound zinc ions in the luminal compartment is essential for the protective action of zinc against E. coli HlyA. This suggests the usage of zinc as therapeutic regimen, while prophylactic intervention by high dietary zinc loads may be less useful.

Quantification of glyphosate and aminomethylphosphonic acid from microbiome reactor fluids.

Glyphosate is one of the most widely used herbicides and it is suspected to affect the intestinal microbiota through inhibition of aromatic amino acid synthesis via the shikimate pathway. In vitro microbiome bioreactors are increasingly used as model systems to investigate effects on intestinal microbiota and consequently methods for the quantitation of glyphosate and its degradation product aminomethylphosphonic acid (AMPA) in microbiome model systems are required. An optimized protocol enables the analysis of both glyphosate and AMPA by simple extraction with methanol:acetonitrile:water (2:3:1) without further enrichment steps. Glyphosate and AMPA are separated by liquid chromatography on an amide column and identified and quantified with a targeted tandem mass spectrometry method using a QTRAP 5500 system (AB Sciex). Our method has a limit of detection (LOD) in extracted water samples of <2 ng/mL for both glyphosate and AMPA. In complex intestinal medium, the LOD is 2 and 5 ng/mL for glyphosate and AMPA, respectively. These LODs allow for measurement at exposure-relevant concentrations. Glyphosate levels in a bioreactor model of porcine colon were determined and consequently it was verified whether AMPA was produced by porcine gut microbiota. The method presented here allows quantitation of glyphosate and AMPA in complex bioreactor fluids and thus enables studies of the impact of glyphosate and its metabolism on intestinal microbiota. In addition, the extraction protocol is compatible with an untargeted metabolomics analysis, thus allowing one to look for other perturbations caused by glyphosate in the same sample.

An advanced RFID-based system to localize gastric and colon cancers during laparoscopic surgery.

We aimed to improve the tumor localization system using radiofrequency identification (RFID) technology used during laparoscopic surgery for gastric and colorectal cancer. To this end, we developed a detection algorithm and designed improvement for the RFID clip. To evaluate the proposed system, a swine-based animal study was conducted, followed by experiments on porcine stomachs and colons using the EASIE-R simulator. The success rates of endoscopic clipping, detection time, and detection accuracy, which is the distance between the detection point and RFID tag, were measured. Results of the in vivo swine animal study showed success in all three clippings and detections of the RFID clips. Results of the 60 RFID endoclip attempts using the EASIE-R simulator showed a total clipping success rate of 85.0% (n = 51/60; stomach, 83.3%, n = 25/30; colon, 86.7%, n = 26/30). The median detection times were 29.2s for the stomach and 25.5s for the colon. The median detection accuracy was 4.0 mm for the stomach and 4.5 mm for the colon. We confirmed that the proposed RFID-based system showed improvements over the system of a previous study. This RFID-based system is effective at localizing gastric and colorectal tumors.

Compression injury of the circular stapler for gastrointestinal end-to-end anastomosis: preliminary in-vitro study.

PurposeThis preliminary in-vitro study was designed to evaluate the risk factors of compression injury from use of a circular stapler for end-to-end anastomosis.MethodsTransparent collagen plates were prepared in dry and wet conditions. Physical properties of collagen plates and porcine colon tissue were examined using a rheometer. Adjustable and fixed-type circular staplers were applied on the collagen plates and the gap distance and compressive pressure were measured during anvil approximation. Tissue injury was evaluated using a compression injury scale. Compression properties were accessed to optimal or overcompression based on gap distance.ResultsUnacceptable injuries were rarely observed on the dry collagens, regardless of compression device. In the adjustable compression, the compressibility ratio was similar between dry and wet collagen. Overcompression and unacceptable injury increased on the wet collagens. In the fixed compression, the compressibility ratio increased significantly and unacceptable injuries were observed in more than 50% of wet collagens. Peak pressure was significantly higher in the fixed-compression types than those of adjustable type. On bivariate correlation analysis, fixed-compression type and wet collagens were respectively associated with overcompression. On multivariate analysis, edematous collagen condition was the most important risk factor and proximal anvil side, fixed compression type, and overcompression were also independent risk factors for unacceptable compression injury.ConclusionIn the edematous tissue condition, unintentional overcompression could be increased and result in tissue injury on the compression line of the circular stapler.

Design of an Impedance-Controlled Hot Snare Polypectomy Device.

This paper goes through the process of first designing a feedback system that allows for the measuring of impedance while using the hot snare polypectomy method. The electrosurgical unit used in this study was the Olympus PSD-30. After the impedance-controlled feedback system was completed, the device was tested under a range of power settings from 10 W–50 W. The test was performed ex vivo using porcine colon samples. Using the information gathered from these tests, a technique of determining the threshold of perforation and implementing a system to automatically stop the applied current from the PSD-30 was developed. The data showed that after an increase in impedance of 25% from that of the initially measured impedance, perforation ensued in the tissue samples. Using this information, the device was programmed to interrupt the PSD-30 at this threshold point. This final design was tested and proved able to automatically prevent the event of perforation from occurring, resulting in the ability to prevent serious complications.

Impairment of electroneutral Na+transport and associated downregulation of NHE3 contributes to the development of diarrhea following in vivo challenge withBrachyspiraspp.

The effect of Brachyspira hyodysenteriae and Brachyspira hampsonii spirochetosis on Na+ transport was assessed in the colon to determine its contribution to diarrheal disease in pigs following experimental infection. Electrogenic and electroneutral Na+ absorption was assessed in Ussing chambers by radiolabeled 22Na flux and pharmacological inhibitory studies. Basal radiolabeled 22Na flux experiments revealed that mucosal-to-serosal flux (Jms) was significantly impaired in B. hyodysenteriae and B. hampsonii-diseased pigs. Inhibition of epithelial sodium channel via amiloride did not significantly reduce electrogenic short-circuit current (Isc) in the proximal, apex, and distal colonic segments of diseased pigs over control pigs, suggesting that a loss of electroneutral Na+ absorption is responsible for diarrheal development. These findings were further supported by significant downregulation of Na+/H+ exchanger (NHE1, NHE2, and NHE3) mRNA expression in the proximal, apex, and distal colonic segments paired with decreased protein expression of the critical NHE3 isoform. The decrease in NHE3 mRNA expression appears not to be attributed to the host's cytokine response as human IL-1α did not modify NHE3 mRNA expression in Caco-2 cells. However, a whole cell B. hampsonii lysate significantly downregulated NHE3 mRNA expression and significantly increased p38 phosphorylation in Caco-2 cells. Together these findings provide a likely mechanism for the spirochete-induced malabsorptive diarrhea, indicated by a decrease in electroneutral Na+ absorption in the porcine colon due to Brachyspira's ability to inhibit NHE3 transcription, resulting in diarrheal disease.NEW & NOTEWORTHY This research demonstrates that diarrheal disease caused by two infectious spirochete spp. is a result of impaired electroneutral Na+ absorption via Na+/H+ exchanger 3 (NHE3) in the porcine colon. Our findings suggest that the decrease in NHE3 mRNA and protein is not likely a result of the host's cytokine response. Rather, it appears that these two Brachyspira spp. directly inhibit the transcription and translation of NHE3, resulting in the development of diarrhea.

A comparative study of hyperelastic constitutive models for colonic tissue fitted to multiaxial experimental testing

For colonic stents design, the interaction with colonic tissue is essential in order to characterize the appropriate radial stiffness which provides a minimum lumen for intestinal transit to be maintained. It is therefore important to develop suitable constitutive models allowing the mechanical behavior of the colon tissue to be characterized.The present work investigates the biomechanical behavior of colonic tissue by means of biaxial tests carried out on different parts of the colonic tract taken from several porcine specimens. Samples from the colonic tract were quasi-statically tensioned using a load-controlled protocol with different tension ratios between the circumferential and the axial directions. Fitting techniques were then used to adjust specific hyperelastic models accounting for the multilayered conformation of the colonic wall and the fiber-reinforced configuration of the corresponding tissues.It was found that the porcine colon changed from a more isotropic to a more anisotropic tissue and became progressively more flexible and compliant in circumferential direction depending on the position along the duct as it approaches the rectum. The best predictive capability of mechanical behavior corresponds to the Four Fiber Family model showing mean values of coefficient of determination R2=0.97, and a normalized root mean square error of εNRMS=0.0814 for proximal spiral samples, and R2=0.89 , εNRMS=0.1600 and R2=0.94 , εNRMS=0.1227 for distal spiral and descending colon samples, respectively. The other analyzed models provide good results for proximal spiral colon specimens, which have a lower degree of anisotropy.The analyzed models with the fitted elastic parameters can be used for more realistic and reliable FE simulations, providing the appropriate framework for the design of optimal devices for the treatment of colonic diseases.

A micro-tattooing device for capsule endoscope using a Wood's metal triggering mechanism

The endoscopic tattooing procedure is essential before surgery in the gastroenterology practice. Because conventional tattooing is conducted by injecting biocompatible ink from outside the human body, a conventional tattooing device is not appropriate for use in the Capsule Endoscope (CE). A compact micro-tattooing device with an optimal triggering mechanism which can be enclosed in the CE is required. Therefore, A micro-tattooing device operated by two conical springs with a Wood's metal-based triggering module is proposed. Needle insertion and ink injection to the submucosal layer of the colon is actuated by triggering mechanism #1. When triggering mechanism #2 is activated, the needle is withdrawn to avoid scratching the internal lumen. Each triggering module is activated by the Joule heating of a Ni-Cr wire with low power consumption to accommodate the CE battery's small capacity. The in-vitro and ex-vivo tests were conducted to confirm the feasibility of the tattooing module. In the in-vitro test, the needle displacement was confirmed to be 3.3 mm. Using extracted porcine colon, the total tattooing procedure was conducted, and the injected ink in the submucosal layer was observed by hemisecting the specimen. Conclusively, the device achieved competitive results, both in terms of power consumption and space constraints.

Endoscopic closure of large colonic perforations with a novel endoscopic clip device: An animal study (with videos).

An endoscopic clip device was newly designed to accomplish the closure of large gastrointestinal defects. The aim of this study was to determine the feasibility and efficacy of this device in an ex vivo experimental setting. This prospective study was conducted in porcine colons (n = 5). A large (3-4 cm) linear full-thickness incision was created using a scalpel externally. The device was used for endoscopic closure. The procedure time, number of clips, and success rate of closure were determined. Ten defects were created in five porcine colons (two incisions in each specimen). Successful closure was achieved in all defects. The mean procedure time was 24.30 ± 4.42 min, the mean leak pressure is 28.30 ± 9.49 mmHg, and the mean number of additional conventional hemostatic clips used was 5.10 ± 0.99. The results indicated that this clip achieved the convenient and reliable closure of large defects in the colon wall in an ex vivo porcine model and seems to be a promising option for closing large gastrointestinal perforations.

Preclinical evaluation of porcine colon resection using hollow core negative curvature fibre delivered ultrafast laser pulses.

Ultrashort pulse lasers offer great promise for tissue resection with exceptional precision and minimal thermal damage. Surgery in the bowel requires high precision and minimal necrotic tissue to avoid severe complications such as perforation. The deployment of ultrashort lasers in minimally invasive or endoscopic procedures has been hindered by the lack of suitable optical fibres for high peak powers. However, recent developments of hollow core microstructured fibres provide potential for delivery of such pulses throughout the body. In this study, analysis of laser ablation via a scanning galvanometer on a porcine colon tissue model is presented. A thermally damaged region (<85 μm) and fine depth control of ablation using the pulse energies 46 and 33 μJ are demonstrated. It is further demonstrated that such pulses suitable for precision porcine colon resection can be flexibly delivered via a hollow core negative curvature fibre (HC-NCF) and again ablation depth can be controlled with a thermally damaged region <85 μm. Ablation volumes are comparable to that of early stage lesions in the inner lining of the colon. This study concludes that the combination of ultrashort pulses and flexible fibre delivery via HC-NCF present a viable route to new minimally invasive surgical procedures.

Enhancement of the safety and efficacy of colorectal endoscopic submucosal dissection using a CO2 laser.

Endoscopic submucosal dissection (ESD) has been at the forefront of international attention as a less invasive treatment for early gastrointestinal cancer. Currently, ESD involves the use of an electrosurgical knife for mucosal incision and subsequent submucosal dissection. However, it has been reported that perforation occurs in approximately 5% of cases. To enhance tissue selectivity with this modality, we focused on applying a laser to ESD (laser ESD). A CO2 laser was chosen as the surgical knife because the saline or sodium hyaluronate solution injected into the submucosal layer during the current ESD procedure has a high absorption coefficient at the wavelength of the CO2 laser. Thus, the purpose of this study is to quantitatively clarify the safety and efficacy of laser ESD for the colon. First, we validated a porcine colon as a model of the human colon in terms of optical and thermal properties. Next, ex vivo experiments on the safety and efficacy of laser ESD were performed. In ex vivo experiments using extracted porcine colon tissue, an incision depth of 0.5-1.0mm was obtained without thermal damage to the muscle layer when the power density was set at 17, 22, or 28W/mm2. In addition, less thermal damage was observed in tissue incised with this method compared with electrosurgical knives. These results might be explained by the strong absorption of the CO2 laser by the saline injected into the submucosa. Therefore, laser ESD is expected to be a safer method for the treatment of early colon cancer.

Quantitative Analysis of 4 × 4 Mueller Matrix Transformation Parameters for Biomedical Imaging

Mueller matrix polarimetry is a potentially powerful technique for obtaining microstructural information of biomedical specimens. Thus, it has found increasing application in both backscattering imaging of bulk tissue samples and transmission microscopic imaging of thin tissue slices. Recently, we proposed a technique to transform the 4 × 4 Mueller matrix elements into a group of parameters, which have explicit associations with specific microstructural features of samples. In this paper, we thoroughly analyze the relationships between the Mueller matrix transformation parameters and the characteristic microstructures of tissues by using experimental phantoms and Monte Carlo simulations based on different tissue mimicking models. We also adopt quantitative evaluation indicators to compare the Mueller matrix transformation parameters with the Mueller matrix polar decomposition parameters. The preliminary imaging results of bulk porcine colon tissues and thin human pathological tissue slices demonstrate the potential of Mueller matrix transformation parameters as biomedical diagnostic indicators. Also, this study provides quantitative criteria for parameter selection in biomedical Mueller matrix imaging.

메시의 부피변화를 이용한 해머링 방식의 대장내시경 로봇 개발

Conventional colonoscopy can cause critical damage such as bleeding and perforation and its safe execution depends on the skill of the operator. Therefore, robotic colonoscopes with efficient locomotion have been investigated for overcoming the limitations of conventional colonoscopy. We present a hammering-based robotic colonoscope utilizing an expandable braided mesh. The robot moves along the colon lumen with a hammering procedure using a piston and secures the proper route using a soft braided mesh. The braided mesh expands through a triggering mechanism with one-directional rotation of a DC motor located outside of the body. To evaluate the locomotion performance, theoretical analysis is conducted taking into account the weight of the robot components. Based on the results, an in-vitro test with a urethane tube and an ex-vivo test using an extracted porcine colon were carried out. In the ex-vivo test, the robot achieves high mobile performance reaching the speed of 3.105 mm/sec in a straight path. Additionally, the locomotion test for the paths with the incline angles of 30° and 45° considering the real colon conditions was carried out and it was found that the proposed robot showed proper locomotion using a soft braided mesh. Thus, the hammering-based locomotion mechanism with an expandable mesh achieves promising mobile performance without any damage of the porcine colon.

Decreased electrogenic anionic secretory response in the porcine colon following in vivo challenge with Brachyspira spp. supports an altered mucin environment.

Brachyspira spp. cause diarrheal disease in multiple animal species by colonization of the colon, resulting in colitis, mucus induction, and disrupted ion transport. Unique to spirochete pathogenesis is the immense production of mucus, resulting in a niche mucin environment likely favoring spirochete colonization. Mucin rheological properties are heavily influenced by anionic secretion, and loss of secretory function has been implicated in diseases such as cystic fibrosis. Here, the effects on the agonist-induced electrogenic anionic secretory response by infectious colonic spirochete bacteria Brachyspira hyodysenteriae and Brachyspira hampsonii were assessed in the proximal, apex, and distal sections of colon in Ussing chambers. Activation of secretion via isoproterenol, carbachol, and forskolin/3-isobutyl-1-methylxanthine demonstrated a significantly decreased change in short-circuit current ( Isc) in Brachyspira-infected pigs in all sections. Tissue resistances did not account for this difference, rather, it was attributed to a decrease in anionic secretion as indicated by a decrease in bumetanide inhibitable Isc. Quantitative RT-PCR and Western blot analyses determined that the major anionic channels of the epithelium were downregulated in diarrheic pigs paired with altered mucin gene expression. The investigated cytokines were not responsible for the downregulation of anion channel gene transcripts. Although IL-1α was upregulated in all segments, it did not alter cystic fibrosis transmembrane conductance regulator (CFTR) mRNA expression in Caco-2 monolayers. However, a whole cell Brachyspira hampsonii lysate significantly reduced CFTR mRNA expression in Caco-2 monolayers. Together, these findings indicate that these two Brachyspira spp. may directly cause a decreased anionic secretory response in the porcine colon, supporting an altered mucin environment likely favoring spirochete colonization. NEW & NOTEWORTHY This research demonstrates for the first time that the niche mucin environment produced by two infectious spirochete spp. is supported by a decrease in the electrogenic anionic secretory response throughout the porcine colon. Our findings suggest that the host's cytokine response is not likely responsible for the decrease in anionic secretory function. Rather, it appears that Brachyspira spp. directly impede ion channel transcription and translation, potentially altering colonic mucin rheological properties, which may favor spirochete colonization.

A Novel 450 nm Semiconductor Blue Laser System for Application in Colon Endoscopic Surgery: An Ex Vivo Study of Laser-Tissue Interactions.

Objective: Our study aimed to detect whether 450 nm blue laser can be applied effectively and safely in endosocopic submucosal dissection (ESD) system for surgery in colonic tissue. Background data: Semiconductor blue laser has been applied in surgery due to its excellent cutting property, however, whether blue laser can be applied in colonic surgery has not been reported. Materials and methods: Porcine colon tissues were vaporized by 450 nm blue semiconductor laser at 10-25 W and at working distances from 0.5 to 3 mm, with a three-dimensional scanning system. Moreover, we designed an ESD model and applied blue laser at 10 W on porcine colonic tissues with this system. Dimensions of the vaporized tissues and coagulation zones were assessed under microscopy. Results: Since the thickness of colonic wall is no more than 1 mm, first we determined the cutting property and safety of blue laser on porcine colon tissue and found that blue laser at 10 W made lesions shallower than 1 mm and the depth of vaporization can be controlled effectively within muscularis mucosa and submucosa. Moreover, a large scale of porcine colonic tissue was vaporized precisely by blue laser at power of 10 W with the ESD system ex vivo. Conclusions: Our results indicate that 450 nm blue laser at 10 W can be well controlled for laser-tissue interaction with excellent cutting efficiency and less thermal damage in adjacent tissues especially side of the submucosa. Therefore, 450 nm semiconductor blue laser could be a safe alternative approach for colonic surgery.

How much force is required to perforate a colon during colonoscopy? An experimental study

IntroductionColonoscopy is a commonly-performed procedure to diagnose pathology of the large intestine. Perforation of the colon is a rare but feared complication. It is currently unclear how much force is actually required to cause such injury nor how this is altered in certain diseases. Our aim was to analyze the forces required to perforate the colon in experiments using porcine tissues. MethodsUsing 3D printing technology, models of two commercially available colonoscope heads were printed under three configurations: straight (I), 90°- bent (L) and fully bent (U). Samples of porcine colon were assessed with the models and configurations under perpendicular and angular load application and these data compared to the maximum force typically exerted by experienced colonoscopists. ResultsThe force required for perforation was significantly lower for the I compared to the L of the larger colonoscope head configuration under angular loading (14.1 vs. 46.5 N). Similar differences were found for linear stiffness when loaded (I vs. L small when loaded perpendicular: 0.8 vs. 2.4 N/mm, I vs. L large when loaded angled 0.7 vs. 2.1 N/mm). The mode and site of failure varied significantly between the scopes, with delamination of the mucosa/submucosa below the sample (96%) for the I, blunt mucosa/submucosa/muscularis failure adjacent to the loading site (77%) for the L, and failure of all colon layers lateral to the loading site (59%) for the U configuration, respectively. Perpendicular and angulated loading resulted in similar load-deformation values. Maximum forces typically exerted by colonoscopists averaged 13.9–27.9 N, depending on the colonoscope model and head configuration. DiscussionThe force required for colon perforation varies depending on the type mode of loading and is likely lower than the force an experienced colonoscopist would exert in daily practice. There is a real risk of perforation, especially when the end of the scope is advancing directly into the colonic wall. The given experimental setup allowed to obtain reliable data of the colon in a standardized scenario, forming the basis for further experiments.

Colorectal endoscopic submucosal dissection using novel articulating devices: a comparative study in a live porcine model.

Colonic endoscopic submucosal dissection (ESD) is time-consuming and bears a high risk of perforation. The aim of the present study was to compare the safety and efficacy between novel articulating devices and conventional ESD in live porcine colon models. Thirty ESDs in ten pigs were carried out at three different locations (15, 25, and 35cm from the anus) by the conventional method (n = 15) and by the new method (n = 15). Procedure times, adverse events (perforation, bleeding), and damage to the muscular layer were recorded, and the ESD time per unit area of the specimens was calculated. The perforation rate using the conventional method was 6.7% (1/15), whereas that using the new method was 0.0%. The number of sites of muscular damage was significantly lower in the new than conventional method (6 vs. 37, respectively; P = 0.024). The mean procedure time was significantly shorter in the new than conventional method (4.6 ± 2.0 vs. 7.0 ± 4.1min/cm2, respectively; P = 0.042). Use of the new ESD method allows for reduced adverse events and a shortened resection time.

Deep learning with cinematic rendering: fine-tuning deep neural networks using photorealistic medical images

Deep learning has emerged as a powerful artificial intelligence tool to interpret medical images for a growing variety of applications. However, the paucity of medical imaging data with high-quality annotations that is necessary for training such methods ultimately limits their performance. Medical data is challenging to acquire due to privacy issues, shortage of experts available for annotation, limited representation of rare conditions and cost. This problem has previously been addressed by using synthetically generated data. However, networks trained on synthetic data often fail to generalize to real data. Cinematic rendering simulates the propagation and interaction of light passing through tissue models reconstructed from CT data, enabling the generation of photorealistic images. In this paper, we present one of the first applications of cinematic rendering in deep learning, in which we propose to fine-tune synthetic data-driven networks using cinematically rendered CT data for the task of monocular depth estimation in endoscopy. Our experiments demonstrate that: (a) convolutional neural networks (CNNs) trained on synthetic data and fine-tuned on photorealistic cinematically rendered data adapt better to real medical images and demonstrate more robust performance when compared to networks with no fine-tuning, (b) these fine-tuned networks require less training data to converge to an optimal solution, and (c) fine-tuning with data from a variety of photorealistic rendering conditions of the same scene prevents the network from learning patient-specific information and aids in generalizability of the model. Our empirical evaluation demonstrates that networks fine-tuned with cinematically rendered data predict depth with 56.87% less error for rendered endoscopy images and 27.49% less error for real porcine colon endoscopy images.

A reel mechanism-based robotic colonoscope with high safety and maneuverability.

At present, the colonoscopy is the most common method of screening for colorectal cancer. However, endoscopists still encounter difficulties with intubation, primarily due to the structural diversity (e.g., path, shape, and size) and viscoelasticity of the colon. Therefore, well-trained, skillful operators are required to overcome these factors and operate colonoscopes without harming patients. In our previous work, we presented a reel mechanism-based robotic colonoscope designed to mitigate the difficulties of conventional colonoscopies. Although we reported excellent mobile performance with respect to the robot, we did not provide an in-depth discussion concerning patient safety. Therefore, in this article, we propose a method of improving robot safety, and this is verified by investigating the static and dynamic forces acting on the colon. In addition, the maneuverability and safety of the robot in the in vitro condition are evaluated. The safety solution is provided by covering the robot's legs with silicone. To evaluate the results, the reaction force according to leg deformation is measured. Then, the force transmitted to the colon is also measured when the robot moves through various environments. Finally, a mobility test on an excised porcine colon is performed to simultaneously verify the robot's maneuverability and safety. We verify that the static and dynamic force acting on the colon is less than the burst force of a human colon. In addition, the maneuverability of the robotic colonoscope shows reliable locomotion performance even with the soft material covering the legs; it has forward velocities of 9.552 ± 1.940mm/s on a flat path. Owing to the reliable locomotion mechanism with the safety-securing silicone, the robot achieves high and reliable maneuverability without any scratches or perforations to the porcine colon.