Classification of probe-based confocal laser endomicroscopy findings in pancreaticobiliary strictures

BACKGROUND AND STUDY AIMS

The accurate diagnosis of indeterminate pancreaticobiliary strictures presents a clinical dilemma. Probe-based confocal laser endomicroscopy (pCLE) offers real-time in vivo microscopic tissue examination that may increase sensitivity for the detection of malignancy. the objective of this study was to develop and validate a standard descriptive classification of pcle in the pancreaticobiliary system.

PATIENTS AND METHODS

A total of 102 patients undergoing endoscopic retrograde cholangiopancreatography (ERCP) with pCLE to assess indeterminate pancreaticobiliary strictures were enrolled in a multicenter registry; 89 of these patients were evaluable. Information and data on the following were collected prospectively: clinical, ERCP, tissue sampling, pCLE, and follow-up. A uniform classification of pCLE findings ("Miami Classification") was developed, consisting of a set of image interpretation criteria. Thereafter, these criteria were tested through blinded consensus review of 112 randomized pCLE videos from 47 patients, and inter-observer variability was assessed in 42 patients .

RESULTS

A consensus definition of the specific criteria of biliary and pancreatic pCLE findings for indeterminate strictures was developed. Single-image interpretation criteria did not have a high enough sensitivity for predicting malignancy. However, combining two or more criteria significantly increased the sensitivity and predictive values. The characteristics most suggestive of malignancy included the following: thick white bands (>20 µm), or thick dark bands (>40 µm), or dark clumps or epithelial structures. These provided sensitivity, specificity, positive predictive value, and negative predictive value of 97%, 33%, 80%, and 80% compared with 48%, 100%, 100%, and 41% for standard tissue sampling methods. Inter-observer variability was moderate for most criteria.

CONCLUSION

The Miami Classification enables a structured, uniform, and reproducible description of pancreaticobiliary pCLE. Combining individual characteristics improves the sensitivity for the detection of malignancy.

Predictive mathematical models of cancer signalling pathways

Complex intracellular signalling networks integrate extracellular signals and convert them into cellular responses. In cancer cells, the tightly regulated and fine-tuned dynamics of information processing in signalling networks is altered, leading to uncontrolled cell proliferation, survival and migration. Systems biology combines mathematical modelling with comprehensive, quantitative, time-resolved data and is most advanced in addressing dynamic properties of intracellular signalling networks. Here, we introduce different modelling approaches and their application to medical systems biology, focusing on the identifiability of parameters in ordinary differential equation models and their importance in network modelling to predict cellular decisions. Two related examples are given, which include processing of ligand-encoded information and dual feedback regulation in erythropoietin (Epo) receptor signalling. Finally, we review the current understanding of how systems biology could foster the development of new treatment strategies in the context of lung cancer and anaemia.

Multimodal endoscopic therapy for multifocal intraepithelial neoplasia and superficial esophageal squamous cell carcinoma - a case series

Local endoscopic procedures are increasingly used and accepted treatments for unifocal superficial esophageal squamous cell carcinoma (SESCC). In multifocal SESCC, esophagectomy with or without chemoradiotherapy is often regarded as standard therapy. However, a combination of local endoscopic resection and new techniques such as radiofrequency ablation may play an increasing role in the treatment of selected patients with multifocal SESCC. The aim of this series was to evaluate the feasibility of a multimodal endoscopic approach. We report a case series of six consecutive patients from a European tertiary center who underwent endoscopic treatment for multifocal SESCC. The treatment comprised endoscopic mucosal resection using the cap technique or endoscopic submucosal dissection, in combination with radiofrequency ablation. The main outcome measure was complete tumor eradication after therapy and during the follow-up period. Using such an approach, complete eradication of cancer was achieved in all patients during follow-up. No major adverse events occurred. In conclusion, in selected patients with multifocal or residual SESCC, local resection techniques in combination with radiofrequency ablation may be safe and potentially curative alternative treatments.

Identifiability and observability analysis for experimental design in nonlinear dynamical models

Dynamical models of cellular processes promise to yield new insights into the underlying systems and their biological interpretation. The processes are usually nonlinear, high dimensional, and time-resolved experimental data of the processes are sparse. Therefore, parameter estimation faces the challenges of structural and practical nonidentifiability. Nonidentifiability of parameters induces nonobservability of trajectories, reducing the predictive power of the model. We will discuss a generic approach for nonlinear models that allows for identifiability and observability analysis by means of a realistic example from systems biology. The results will be utilized to design new experiments that enhance model predictiveness, illustrating the iterative cycle between modeling and experimentation in systems biology.

Probe-based confocal laser endomicroscopy compared with standard four-quadrant biopsy for evaluation of neoplasia in Barrett's esophagus

BACKGROUND AND STUDY AIMS

Surveillance of Barrett's esophagus includes endoscopic inspection with biopsy of suspicious lesions followed by four-quadrant biopsy of the remaining mucosa. We assessed the ability of probe-based confocal laser endomicroscopy (pCLE) to replace biopsy in the endoscopic evaluation of patients with Barrett's esophagus in a prospective and controlled setting.

PATIENTS AND METHODS

A total of 68 patients who were referred for endoscopic assessment of Barrett's esophagus were included across three centers. pCLE recordings were interpreted live during the examination as well as in a blinded manner at least 3 months after endoscopy. pCLE diagnosis of neoplasia based on pre-defined criteria was compared with histopathology from suspicious as well as four-quadrant biopsies.

RESULTS

A total of 670 pairs of biopsies and pCLE video sequences were available for analysis, with neoplasia (high-grade dysplasia or cancer) being histologically diagnosed in 8.3 %. Specificity and negative predictive value of pCLE in excluding neoplasia was 0.97 (90 %CI 0.95 - 0.98) and 0.93 (0.91 - 0.95) for the blinded evaluation, and 0.95 (0.90 - 0.98) and 0.92 (0.90 - 0.94) for the on-site assessment. Positive predictive values (PPVs) and sensitivity were rather poor for both settings (46 %/28 % [blinded] and 18 %/12 % [on-site], respectively).

CONCLUSIONS

pCLE can be regarded as non-inferior to endoscopic biopsy in excluding neoplasia of Barrett's esophagus mucosa. However, due to its low PPV and sensitivity, pCLE may currently not replace standard biopsy techniques for the diagnosis of Barrett's esophagus and associated neoplasia. Further technical development of pCLE and a better understanding of its role in relation to other imaging technologies are necessary.

Natural orifice transluminal endoscopic surgery: cardiopulmonary safety of transesophageal mediastinoscopy

BACKGROUND AND STUDY AIMS

Physiological reactions during natural orifice transluminal endoscopic surgery (NOTES) mediastinoscopy may lead to cardiorespiratory depression. The aim of the current study was to assess cardiopulmonary changes during transesophageal mediastinoscopy in an acute porcine model.

METHODS

Transesophageal mediastinoscopy was performed under general anesthesia in eight female pigs with a bodyweight of 39 +/- 6 kg. Mediastinal access was achieved via a submucosal tunnel. The cardiac index and global end-diastolic volume index (reflecting preload) were measured every 3 minutes by transpulmonary thermodilution. The following parameters were also recorded: mediastinal pressure, heart rate, mean arterial pressure, systemic vascular resistance index (SVRI; reflecting afterload), peak inspiratory pressure, pH, pCO (2), and pO (2).

RESULTS

In three animals, small tears in the parietal pleura resulted in tension pneumothoraces. The associated cardioplumonary deterioration was fatal in one pig. The other two pigs recovered after decompression with a chest tube. In the remaining five animals there were only mild hemodynamic and respiratory changes during mediastinoscopy. There was a significant ( P = 0.005) but minor transient fall in cardiac index, which correlated with a small rise in SVRI (r = - 0.857, P < 0.001). In the pigs with uncomplicated mediastinoscopy, on-demand insufflation via the endoscope resulted in median mediastinal pressures of 4.5 mm Hg (range 2.3 - 10.2 mm Hg). Overall, mediastinal and thoracic structures could be identified without difficulty via the transesophageal approach.

CONCLUSIONS

NOTES mediastinoscopy carries a substantial risk of inadvertent development of a pneumothorax. Otherwise, it leads to negligible hemodynamic and pulmonary changes. In conclusion, close monitoring for the presence of a pneumothorax during NOTES mediastinoscopy appears to be mandatory.

Wetting of Sapphire by a Supercooled Silicon Droplet

A small piece of silicon was melted in vacuum in a high precision spherical depression of a heated (0001) oriented sapphire substrate. The droplet was observed from above by use of a microscope equipped with a CMOS video camera. Above the melting point (1687 K) it exhibited small but rapid breathing mode fluctuations. The frequency of these fluctuations could be slowed down by supercooling the droplet to about 80 K below the melting temperature, allowing a detailed study of the effect. An unusual contour structure with a threefold rotation symmetry was observed, when the droplet had spread to its maximum contour diameter. This pattern can be related to the ditrigonal-scalenohedral 3¯m symmetry of the sapphire crystal.

Infected necrosis in severe pancreatitis--combined nonsurgical multi-drainage with directed transabdominal high-volume lavage in critically ill patients

BACKGROUND

Infection of pancreatic necrosis is a life-threatening complication during the course of acute pancreatitis. In critically ill patients, surgical or extended endoscopic interventions are associated with high morbidity and mortality. Minimally invasive procedures on the other hand are often insufficient in patients suffering from large necrotic areas containing solid or purulent material. We present a strategy combining percutaneous and transgastric drainage with continuous high-volume lavage for treatment of extended necroses and liquid collections in a series of patients with severe acute pancreatitis.

PATIENTS AND METHODS

Seven consecutive patients with severe acute pancreatitis and large confluent infected pancreatic necrosis were enrolled. In all cases, the first therapeutic procedure was placement of a CT-guided drainage catheter into the fluid collection surrounding peripancreatic necrosis. Thereafter, a second endosonographically guided drainage was inserted via the gastric or the duodenal wall. After communication between the separate drains had been proven, an external to internal directed high-volume lavage with a daily volume of 500 ml up to 2,000 ml was started.

RESULTS

In all patients, pancreatic necrosis/liquid collections could be resolved completely by the presented regime. No patient died in the course of our study. After initiation of the directed high-volume lavage, there was a significant clinical improvement in all patients. Double drainage was performed for a median of 101 days, high-volume lavage for a median of 41 days. Several endoscopic interventions for stent replacement were required (median 8). Complications such as bleeding or perforation could be managed endoscopically, and no subsequent surgical therapy was necessary. All patients could be dismissed from the hospital after a median duration of 78 days.

CONCLUSION

This approach of combined percutaneous/endoscopic drainage with high-volume lavage shows promising results in critically ill patients with extended infected pancreatic necrosis and high risk of surgical intervention. Neither surgical nor endoscopic necrosectomy was necessary in any of our patients.

Miniprobe confocal laser microscopy for the detection of invisible neoplasia in patients with Barrett's oesophagus

OBJECTIVE

The biggest challenge in endoscopic surveillance of Barrett's oesophagus is better detection of neoplasia in mucosa of normal macroscopic appearance. We evaluated in vivo miniprobe confocal laser microscopy (CLM) for the detection of invisible Barrett's neoplasia.

DESIGN

Prospective two-centre trial in two phases: phase I to establish criteria of Barrett's neoplasia and phase II to test these criteria.

PATIENTS AND INTERVENTION

296 biopsy sites in 38 consecutive patients with Barrett's oesophagus (mean age 62.1 years, 89.5% men, median length of the Barrett's oesophagus, 3 cm) were examined with standard high-resolution endoscopy and by miniprobe CLM, with precise matching of CLM recordings to biopsy sites. CLM image criteria for normal versus neoplastic Barrett's oesophagus were established from 95 biopsies of 15 patients (phase I); these criteria were then prospectively tested on 201 biopsies from the remaining patients without visible focal changes (phase II). All 201 CLM video recordings from phase II cases were randomised and blindly evaluated by two gastroenterologists.

MAIN OUTCOME MEASURE

The primary endpoints were accuracy values in diagnosing HGIN or early carcinoma (EC) on a per-biopsy basis. Secondary endpoints included inter-observer agreement.

RESULTS

All initially defined miniprobe CLM criteria (phase I) were significantly more frequently detected in HGIN/EC sites compared with sites with no or low grade neoplasia (phase II). In a per-biopsy analysis, sensitivity and specificity for two independent investigators were 75.0% and 88.8%, and 75.0% and 91.0%, respectively, translating at best into a positive predictive value of 44.4% and a negative predictive value of 98.8%. Inter-observer agreement was good (kappa 0.6).

CONCLUSION

Miniprobe CLM showed a high negative predictive value for the diagnosis of endoscopically invisible neoplasia in Barrett's oesophagus; sensitivity, however, has still to be improved.

Confocal laser scanning fluorescence microscopy for in vivo determination of microvessel density in Barrett's esophagus

BACKGROUND AND STUDY AIMS

Angiogenesis has been reported to be an essential step in the progression of cancers arising from Barrett's esophagus. Confocal laser scanning microscopy (CLM) has the potential to perform in vivo microscopy to detect angiogenesis and determine microvessel density (MVD). We aimed therefore to use this new promising imaging tool for the evaluation of MVD in Barrett's esophagus and associated neoplasia.

PATIENTS AND METHODS

We enrolled 20 patients with Barrett's esophagus. CLM sequences were recorded from pre-marked areas using argon beamer coagulation spots after intravenous application of fluorescein. Sequences had to be recorded within the first 8 minutes of injection. Biopsies were taken from the same areas for standard histopathology. All CLM sequences were put into a random order and analyzed by a single investigator who was blinded to any clinical or histopathological data. Five still images per sequence were analyzed for MVD using a specially designed software algorithm. The primary endpoint was determination of vessel diameter and MVD in relation to neoplastic or non-neoplastic Barrett's esophagus.

RESULTS

We evaluated 750 still CLM images from 150 sequences/biopsy sites. Histopathology revealed 69 biopsies as non-neoplastic Barrett's esophagus (46.0 %), 11 as neoplastic Barrett's esophagus (7.3 %), 64 as cardiac mucosa (42.7 %), and six as squamous mucosa (4.0 %). Mean vessel diameter as determined by CLM was similar in all four groups (P = 0.2). However, MVD was significantly higher in CLM sequences of neoplastic Barrett's esophagus compared with benign conditions (neoplastic Barrett's esophagus 23.6 %; Barrett's esophagus 14.2 %; cardiac mucosa 15.8 %; squamous epithelium 20.6 %; neoplastic Barrett's esophagus vs. Barrett's esophagus P < 0.001, T-test).

CONCLUSION

Fibered fluorescein-guided CLM helps to detect angiogenesis in malignant and non-malignant Barrett's esophagus in vivo. These data might help to improve the diagnostic yield of detecting Barrett's neoplasia but also to facilitate monitoring of antiangiogenetic therapy.

Coefficient of tangential restitution for viscoelastic spheres

The collision of frictional granular particles may be described by an interaction force whose normal component is that of viscoelastic spheres while the tangential part is described by the model by Cundall and Strack (Géotechnique 29, 47 (1979)) being the most popular tangential collision model in Molecular Dynamics simulations. Albeit being a rather complicated model, governed by 5 phenomenological parameters and 2 independent initial conditions, we find that it is described by 3 independent parameters only. Surprisingly, in a wide range of parameters the corresponding coefficient of tangential restitution, epsilont, is well described by the simple Coulomb law with a cut-off at epsilont = 0. A more complex behavior of the coefficient of restitution as a function on the normal and tangential components of the impact velocity, gn and gt, including negative values of epsilont, is found only for very small ratio gt/gn. For the analysis presented here we neglect dissipation of the interaction in normal direction.