Philip Mewes

Semantic and topological classification of images in magnetically guided capsule endoscopy

Magnetically-guided capsule endoscopy (MGCE) is a nascent technology with the goal to allow the steering of a capsule endoscope inside a water filled stomach through an external magnetic field. We developed a classification cascade for MGCE images with groups images in semantic and topological categories. Results can be used in a post-procedure review or as a starting point for algorithms classifying pathologies. The first semantic classification step discards over-/under-exposed images as well as images with a large amount of debris. The second topological classification step groups images with respect to their position in the upper gastrointestinal tract (mouth, esophagus, stomach, duodenum). In the third stage two parallel classifications steps distinguish topologically different regions inside the stomach (cardia, fundus, pylorus, antrum, peristaltic view). For image classification, global image features and local texture features were applied and their performance was evaluated. We show that the third classification step can be improved by a bubble and debris segmentation because it limits feature extraction to discriminative areas only. We also investigated the impact of segmenting intestinal folds on the identification of different semantic camera positions. The results of classifications with a support-vector-machine show the significance of color histogram features for the classification of corrupted images (97%). Features extracted from intestinal fold segmentation lead only to a minor improvement (3%) in discriminating different camera positions.

Chromoendoscopy in magnetically guided capsule endoscopy

BackgroundDiagnosis of intestinal metaplasia and dysplasia via conventional endoscopy is characterized by low interobserver agreement and poor correlation with histopathologic findings. Chromoendoscopy significantly enhances the visibility of mucosa irregularities, like metaplasia and dysplasia mucosa. Magnetically guided capsule endoscopy (MGCE) offers an alternative technology for upper GI examination. We expect the difficulties of diagnosis of neoplasm in conventional endoscopy to transfer to MGCE. Thus, we aim to chart a path for the application of chromoendoscopy on MGCE via an ex-vivo animal study.MethodsWe propose a modified preparation protocol which adds a staining step to the existing MGCE preparation protocol. An optimal staining concentration is quantitatively determined for different stain types and pathologies. To that end 190 pig stomach tissue samples with and without lesion imitations were stained with different dye concentrations. Quantitative visual criteria are introduced to measure the quality of the staining with respect to mucosa and lesion visibility. Thusly determined optimal concentrations are tested in an ex-vivo pig stomach experiment under magnetic guidance of an endoscopic capsule with the modified protocol.ResultsWe found that the proposed protocol modification does not impact the visibility in the stomach or steerability of the endoscopy capsule. An average optimal staining concentration for the proposed protocol was found at 0.4% for Methylene blue and Indigo carmine. The lesion visibility is improved using the previously obtained optimal dye concentration.ConclusionsWe conclude that chromoendoscopy may be applied in MGCE and improves mucosa and lesion visibility. Systematic evaluation provides important information on appropriate staining concentration. However, further animal and human in-vivo studies are necessary.

On-the-fly Detection of Images with Gastritis Aspects in Magnetically-Guided Capsule Endoscopy

Capsule Endoscopy (CE) was introduced in 2000 and has since become an established diagnostic procedure for the small bowel, colon and esophagus. For the CE examination the patient swallows the capsule, which then travels through the gastrointestinal tract under the influence of the peristaltic movements. CE is not indicated for stomach examination, as the capsule movements can not be controlled from the outside and the entire surface of the stomach can not be reliably covered. Magnetically-guided capsule endoscopy (MGCE) was introduced in 2010. For the MGCE procedure the stomach is filled with water and the capsule is navigated from the outside using an external magnetic field. During the examination the operator can control the motion of the capsule in order to obtain a sufficient number of stomach-surface images with diagnostic value. The quality of the examination depends on the skill of the operator and his ability to detect aspects of interest in real time. We present a novel computer-assisted diagnostic-procedure (CADP) algorithm for indicating gastritis pathologies in the stomach during the examination. Our algorithm is based on pre-processing methods and feature vectors that are suitably chosen for the challenges of the MGCE imaging (suspended particles, bubbles, lighting). An image is classified using an ada-boost trained classifier. For the classifier training, a number of possible features were investigated. Statistical evaluation was conducted to identify relevant features with discriminative potential. The proposed algorithm was tested on 12 video sequences stemming from 6 volunteers. A mean detection rate of 91.17% was achieved during leave-one out cross-validation.

Chromoendoscopy With Automatic Lesion Enhancement in Magnetically Guided Capsule Endoscopy: A Feasibility Study

G A A b st ra ct s for ability to detect and quantify DSS-induced acute colonic inflammation or chronic colitis in 129SvEv IL-10 null mice. We hypothesized that probes would differ in specificity or sensitivity for detection of inflammation. Methods: DSS-treated mice, IL-10 null mice with chronic colitis, and H2O controls were fed a liquid diet (Nutren 1.0 Fiber:dH2O, 1:1) for 4 days to clear GI tract of solid feces. WT mice were given 3% DSS for 5 days and studied 4 days later, a time of known severe colonic inflammation. Probes were given by retroorbital injection. In Vivo imaging was performed with an FMT 2500 LX imaging system. Intestinal tissues were dissected immediately after In Vivo imaging, imaged fresh or after fixation to test if NIRF signal is preserved in fixed tissues. Inflammation detected by probe activation was verified by H&E staining and confocal microscopy. NIRF signal intensity was quantified using 3D region of interest (ROI) analysis In Vivo or 2D ROI ex vivo. Results: (1) All 7 probes were tested In Vivo and ex vivo in DSS model. Several probes yielded significantly increased fluorescence signal (p<0.05) in colon of diseased mice versus H2O controls. Most sensitive probes were used and confirmed in IL-10 null mice. (2) In Vivo Cat K 680 FAST (152±14 vs. 82±5 pmol in fluorochromes, p<0.05) and MMPSense 680 (134±23 vs. 72±14 pmol in fluorochromes, p=0.06) probes yielded significantly higher NIRF signal in inflammation/colitis models vs. controls. Signal was localized to colon by coregistration with MRI. (2) Ex vivo, all 7 probes yielded significant increases in NIRF signal which was highest with MMPSense 680 (193.3% increase vs. controls) and cathepsin based probes (>100% increase vs. controls). (3) Ex vivo fluorescence signal was preserved by appropriate fixation. H&E staining and confocal microscopy confirmed inflammation detected by NIRF probes. NIRF signal intensity and colitis score were strongly correlated (r = 0.87). Conclusions: We developed a new In Vivo method for valid detection and quantification of GI inflammation using activatable NIRF probes in living animals. Cat K 680 FAST andMMPSense 680 probes were the most sensitive for detection and quantification of acute inflammation In Vivo and ex vivo. This approach is useful for In Vivo or ex vivo monitoring and quantification of murine inflammatory bowel diseases. 1 Zhang, Gastrointest Endosc 2008 68 520, 2 Marten, Gastroenterology 2002 122 406.

First Study With a MGCE Simulator: Is There a Benefit of Chromoendoscopy in Magnetically Guided Capsule Endoscopy?

gastroscopy in 6/10 patients (60% p=1), whereas no patient had ascites (p=0.21). VCE still showed small bowel lesions in 7/10 patients (p=0.21), . CONCLUSION: In our study VCE allowed the identification of small bowel lesions in all patients with portal hypertension. TIPS effectively reduces presence and severity of oesophageal varices, but the reduction of small bowel lesions, congestive gastropathy.and ascites was not significant, possibly due to the small patient series. The role of differing post-TIPS intervals should also be evaluated.