Automatic feature generation in endoscopic images

Motivation

Fiber optic endoscopy is essential for minimally invasive surgery, but endoscopic images are very challenging for computer vision algorithms, since they contain many effects like tissue deformations, specular reflections, smoke, variable illumination and field of view. We developed a method to extract features from endoscopic images usable for scene analysis and classification. These features could be used with data from other sensors for workflow analysis and recognition.

Materials and methods

Evolutionary reinforcement learning that automatically computes good features, making it possible to classify endoscopic images into their respective surgical phases. It is especially designed to abstract the relevant information from the highly noisy images automatically.

Results

Automatic feature extraction was used to classify images from endoscopic cholecystectomies into their respective surgical phases. These automatically computed features perform better than some classical features from computer vision. The automated feature extraction process enables reasonable classification rates for complex and difficult images where no good features are known.

Conclusion

We developed an automatic method that extracts features from images for use in classification. The method was applied to endoscopic images yielding promising results and demonstrating its feasibility under demanding conditions.     

Long-term outcome of endoscopic therapy in patients with bile duct injury after cholecystectomy

Background and Aim:  Bile duct lesions, including leaks and strictures, are immanent complications of open or laparoscopic cholecystectomy. Endoscopic procedures have gained increasing potential as the treatment of choice in the management of postoperative bile duct injuries.
Methods:  Between January 1996 and December 2006, 44 patients with biliary leakages and 12 patients with biliary strictures after cholecystectomy were identified by analyzing the endoscopic retrograde cholangiopancreatography database, clinical records, and cholangiograms. The long-term follow up of endoscopic treatment in biliary lesions after cholecystectomy was evaluated by this retrospective study.
Results:  In 34 of 35 patients (97%) with peripheral bile duct leakages, endoscopic therapy was successful. Transpapillary endoprothesis and/or nasobiliary drainage were removed after 31 (5–399) days. After stent removal, the median follow-up period was 81 (11–137) months. In patients with central bile duct leakages, the success rate after median 90 (4–145) days of endoscopic therapy was 66.7% (6/9 patients). The median follow up after stent removal in six successfully treated patients was 70 (48–92) months. Eleven of 12 patients (91.6%) with bile duct strictures had successfully completed stent therapy. The follow-up period of this patient group was 99 (53–140) months.
Conclusions:  Endoscopic treatment of bile duct lesions after cholecystectomy is effective, particularly in patients with peripheral bile duct leakages and bile duct strictures. Therefore, it should be the first-line therapy used in these patients. Although endoscopic management is less successful in patients with central bile duct leakages, an attempt is warranted.     

Cell culture tests for assessing the tolerance of soft tissue to variously modified titanium surfaces

The aim of our research project was to achieve an improvement in the integration of enossal dental implants in the region of peri-implantary soft tissue. Improvement in the adhesion of the gingiva of the surface of enossal implants was to be achieved by modification of the titanium surface. The effect of different modifications on the biocompatibility of the modified titanium surfaces was tested: sulfur dioxide plasma treatment of titanium; acetylene plasma treatment of titanium followed by sulfur dioxide plasma etching; plasma nitration of titanium; replacement of titanium by glycidoxypropyltrimethoxy silane; coating titanium with poly[(ethene-co-vinyl acetate)-graft-vinyl chloride] and coating titanium with fibronectin. Determination of the chemical composition of the surface was carried out using X-ray photospectroscopy. The adsorption of fibronectin at the surface of the titanium was tested using an Enzyme Linked Immunosorbent Assay. In selected in vitro tests with human gingival fibroblasts, cell morphology was assessed using scanning electron microscopy and light microscopy. Cell proliferation and protein synthesis, as well as the activity of mitochondrial dehydrogenases were evaluated. By means of centrifugation and by determining initial cell adhesion, the adhesion of gingival fibroblasts was investigated. According to the kind of modification made to the titanium surfaces, it was possible to observe differences in the cellular behavior of gingiva fibroblasts on the differently modified surfaces of the implants. Coating the titanium using fibronectin produced optimization of cell growth and improvement in the adhesion of gingiva fibroblasts to the implant surface. In contrast, modification of the titanium with poly[(ethene-co-vinyl acetate)-graft-vinyl chloride] generally resulted in a deterioration of the biocompatibility of the surface. A marked correlation between the cellular compatibility of the modified titanium and the surface modification made did not become apparent. One reason for this is the large number of parameters determining the interaction between implant and tissue.     

Histopathology studies in human malignant melanomas of the choroid after unsuccessful treatment with 106Ru/106Rh ophthalmic applicators

Choroidal malignant melanomas were examined after unsuccessful brachytherapy with ¹⁰⁶Ru/¹⁰⁶Rh ophthalmic plaques. The histologic findings were compared with those obtained in non-irradiated melanomas similar in size and location. Both groups revealed no significant clinical difference apart from the lower average age of the irradiated patients. Some of the histologic features (scar formation, changes in the distribution of cell types, rate of mitosis) represented reactions to irradiation. No single histologic feature was strongly correlated to the irradiated group. The phenomenon of radioinsensitivity observed in some malignant melanomas cannot be fully elucidated using conventional histologic methods.Offprint requests to: H. Klaus     

Lipopolysaccharides and leukotriene B4 induce independently regulated electrophysiological and immunological responses in cultured astrocytes

Astrocytes play an important role in immunological processes within the central nervous system. They are able to produce cytokines like interleukin 6 (IL-6) and depolarize substantially after stimulation stimulation by lipopolysaccharides (LPS) or leukotriene B₄ (LTB₄). Therefore, we investigated the coupling between these immunological and electrophysiological processes. Amiloride (250 μM), a blocker of various Na⁺ transport systems, inhibited LPS (5 μg/ml)-induced depolarization, whereas the LPS-induced release of IL-6 was unaffected, indicating different intracellular regulatory mechanisms. LTB₄ (1.0 μM) induced a depolarization of a similar degree but mediated by a different ionic mechanism and failed to induce a detectable IL-6 release. Dexamethasone (1.0 μM) and cycloheximide (2.0 μM) specifically reduced LTB₄-induced depolarization, while LPS-induced depolarization was unaffected, providing further evidence for different regulatory pathways. Neither the depolarization nor the immunological stimuli served as a proliferation signal. These data demonstrate that independent immunological and electrophysiological responses with specific intracellular regulation are evoked after stimulation with LPS or LTB₄. With respect to functional disturbance of depolarized glial cells, e.g. in maintaining local ionic homeostasis, neuronal excitability may be affected indirectly and by this way account for the apperance of neurological symptons during inflammatory CNS diseases.     

GABA and glutamate receptor development of cultured neurons from rat hippocampus, septal region, and neocortex

The early development of functionally active GABA and glutamate receptors on neurons from hippocampus, septal region, and neocortex of embryonic rats were studied using primary dissociated serum-free cell cultures. The responses to GABA and glutamate, applied to individual neurons by pressure ejection, were tested at different developmental stages, starting at 1 day in vitro (DIV) until 3 weeks. In all three types of neuronal cultures, the GABAA-receptor developed prior to the glutamate receptors, and after 9 DIV most of the neurons were sensitive to both GABA and glutamate. N-methyl-D-aspartate (NMDA) and non-NMDA receptor subtypes of the glutamate receptors could be distinguished in hippocampal cultures. The development of GABA and glutamate receptors on septal region neurons appeared to be delayed as compared to hippocampal neurons. In neocortical cultures the majority of neurons was sensitive to GABA just after plating, whereas the sensitivity to glutamate was retarded. The differences in GABA and glutamate receptor development among these three neuronal cultures provide evidence that the appearance of transmitter receptors on cultured neurons is predominantly determined by intrinsic mechanisms rather than by environmental conditions. The proportion of spontaneously active networks in these cultures increased with a time course very similar to the rise in glutamate-sensitive neurons suggesting that functional active glutamate receptors may be involved in the generation of spontaneous activity.     

Lifetime of alumina- and zirconia ceramics used for crown and bridge restorations

The lifetime of a ceramic is dependent on the presence of incidental cracks and their gradual propagation under the conditions of the oral cavity. The objective of this study was to examine the long-term strength of glass-infiltrated alumina- and various zirconia ceramics currently used in CAD/CAM systems to manufacture crown and bridge frameworks. Fracture mechanics were applied to determine characteristic strength (sigma(omicron)), Weibull modulus (m), fracture toughness (K(Ic)), and the subcritical crack growth parameters n and B. Based on these parameters, lifetime diagrams were generated which allowed the evaluation of the long-term behavior. The results showed that in a moist environment, the glass-infiltrated alumina- and some zirconia ceramics have a high susceptibility to subcritical crack growth. Zirconia ceramics with an alumina oxide content of 0.25 wt %, however, exhibited the highest initial and most favorable long-term strength, and should therefore be suitable for crown and bridge restorations.     

Isoflavones--safe food additives or dangerous drugs?

The sales volume of products containing isoflavone has increased since the publication of the Women's Health Initiative. The many apparently contradictory results published on the effects of isoflavones on a variety of estrogen-regulated organs point to both beneficial as well as adverse effects on human health. It is of particular importance that psychovegetative climacteric complaints such as hot flushes are, if at all, only slightly influenced by isoflavones. The substances appear to have weak anti-osteoporotic effect. Their anti-atherosclerotic action is debatable, as not all authors find any beneficial effect on lipids. Most importantly, there is dispute as to whether isoflavones derived from soy or red clover have negative, positive or any effect at all on the mammary gland or endometrium. It is beyond any doubt that soy products may have cancer preventing properties in a variety of organs including the mammary gland. However, these properties may only be exerted if the developing organ was under the influence of isoflavones during childhood and puberty. This may also explain the often quoted "Japanese Phenomenon", the fact that breast cancer occurs to a lesser extent in Japanese women. When administered to isoflavone "inexperienced" women at the time of menopause, the phytoestrogens appear to share the same effects as estrogen used in classical preparations for hormone replacement therapy, i.e. they may stimulate the proliferation of endometrial and mammary gland tissue with at present unknown and unpredictable risk to these organs. Therefore, the following question arises for the clinician: Why should soy or red clover products containing isoflavone be recommended, if the positive effects are only negligible but the adverse effects serious?     

Wireless live streaming video of surgical operations: an evaluation of communication quality

We evaluated a mobile video system for surgical teleconsultation. A video streaming server in the operating room transmitted video and audio to a hand-held computer (personal digital assistant [PDA]) over a wireless local area network. Two groups of 20 surgeons (each with 12 qualified surgeons and eight surgeons between the 2nd and the 4th year of training) participated in the tests. For voice transmission, correct understanding of numbers was achieved in 100% of the cases (n = 1000) and 98% of medical terms (n = 400). The quality of the video displayed on the PDA was assessed by the recognition of different operating room scenarios. Only 62% (SD 17) of the structures were identified clearly on the hand-held device (n = 400). The accuracy improved to 78% (SD 15) (n = 400) if the same scenario was observed on a larger (50 cm) video screen (p < 0.001). Accuracy was significantly better if audio conversation was possible. The quality evaluation by the consultants showed that the PDA display size and quality were sufficient for clinical use.