Robust registration procedures for endoscopic imaging

Abstract This paper presents a robust algorithm for calibration and system registration of endoscopic imaging devices. The system registration allows us to map accurately each point in the world coordinate system into the endoscope image and vice versa to obtain the world line of sight for each image pixel. The key point of our system is a robust linear algorithm based on singular value decomposition (SVD) for estimating simultaneously two unknown coordinate transformations. We show that our algorithm is superior in terms of robustness and computing efficiency to iterative procedures based on Levenberg-Marquardt optimization or on quaternion approaches. The algorithm does not require the calibration pattern to be tracked. Experimental results and simulations verify the robustness and usefulness of our approach. They give an accuracy of less than 0.7 mm and a success rate >99%. We apply the calibrated endoscope to the neurosurgical relevant case of red out, where in spite of the complete loss of vision the surgeon gets visual aids in the endoscope image at the actual position, allowing him/her to manoeuvre a coagulation fibre into the right position. Finally we outline how our registration algorithm can be used also for standard registration applications (establish the mapping between two sets of points). We propose our algorithm as a linear, non-iterative algorithm also for projective transformations and for 2D-3D-mappings. Thus it can be seen as a generalization of the well-known Umeyama registration algorithm

SACOBRA with Online Whitening for Solving Optimization Problems with High Conditioning

Real-world optimization problems often have expensive objective functions in terms of cost and time. It is desirable to find near-optimal solutions with very few function evaluations. Surrogate-assisted optimizers tend to reduce the required number of function evaluations by replacing the real function with an efficient mathematical model built on few evaluated points. Problems with a high condition number are a challenge for many surrogate-assisted optimizers including SACOBRA. To address such problems we propose a new online whitening operating in the black-box optimization paradigm. We show on a set of high-conditioning functions that online whitening tackles SACOBRA's early stagnation issue and reduces the optimization error by a factor between 10 to 1e12 as compared to the plain SACOBRA, though it imposes many extra function evaluations. Covariance matrix adaptation evolution strategy (CMA-ES) has for very high numbers of function evaluations even lower errors, whereas SACOBRA performs better in the expensive setting (less than 1e03 function evaluations). If we count all parallelizable function evaluations (population evaluation in CMA-ES, online whitening in our approach) as one iteration, then both algorithms have comparable strength even on the long run. This holds for problems with dimension D Algorithms and the Foundations of Software technolog

Anomaly Detection in Electrocardiogram Readings with Stacked LSTM Networks

Real-world anomaly detection for time series is still a challenging task. This is especially true for periodic or quasi-periodic time series since automated approaches have to learn long-term correlations before they are able to detect anomalies. Electrocardiography (ECG) time series, a prominent real-world example of quasi-periodic signals, are investigated in this work. Anomaly detection algorithms often have the additional goal to identify anomalies in an unsupervised manner. In this paper we present an unsupervised time series anomaly detection algorithm. It learns with recurrent Long Short-Term Memory (LSTM) networks to predict the normal time series behavior. The prediction error on several prediction horizons is used to build a statistical model of normal behavior. We propose new methods that are essential for a successful model-building process and for a high signal-to-noise-ratio. We apply our method to the well-known MIT-BIH ECG data set and present first results. We obtain a good recall of anomalies while having a very low false alarm rate (FPR) in a fully unsupervised procedure. We compare also with other anomaly detectors (NuPic, ADVec) from the state-of-the-art.Algorithms and the Foundations of Software technolog

Solving the G-problems in less than 500 iterations: Improved efficient constrained optimization by surrogate modeling and adaptive parameter control

Algorithms and the Foundations of Software technolog

Electromagnetic Form Factors of the Nucleon in a Relativistic Quark Pair Creation Model

We study the effects of the | qqq q\bar{q} > component of the hadronic wave function on the description of the electromagnetic structure of the nucleon. Starting with a qqq baryonic wave function which describes the baryonic and mesonic low energy spectrum, the extra q\bar{q} pair is generated through a relativistic version of the 3P_0 model. It is shown that this model leads to a renormalization of the quark mass that allows one to construct a conserved electromagnetic current. We conclude that these dynamical relativistic corrections play an important role in reproducing the Q2 dependence of the electromagnetic form factors at low Q^2.Comment: 15 pages, 3 figures. Minor change

Photo- and Electroproduction of Eta Mesons

Eta photo- and electroproduction off the nucleon is investigated in an effective lagrangian approach that contains Born terms and both vector meson and nucleon resonance contributions. In particular, we review and develop the formalism for coincidence experiments with polarization degrees of freedom. The different response functions appearing in single and double polarization experiments have been studied. We will present calculations for structure functions and kinematical conditions that are most sensitive to details of the lagrangian, in particular with regard to contributions of nucleon resonances beyond the dominant $S_{11}$(1535) resonance.Comment: 24 pages RevTeX/LaTeX2.09, NFSS1, 13 figures (in separate file (tar,gzip and uue)), accepted for publication in Z. Phys.

Hadronic properties of the S_{11}(1535) studied by electroproduction off the deuteron

Properties of excited baryonic states are investigated in the context of electroproduction of baryon resonances off the deuteron. In particular, the hadronic radii and the compositeness of baryon resonances are studied for kinematic situations in which their hadronic reinteraction is the dominant contribution. Specifically, we study the reaction $d(e,e'S_{11})N$ at $Q^2\ge 1 GeV^2$ for kinematics in which the produced hadronic state reinteracts predominantly with the spectator nucleon. A comparison of constituent quark model and effective chiral Lagrangian calculations of the $S_{11}$ shows substantial sensitivity to the structure of the produced resonance.Comment: 24 pages, 5 figure

Intracoronary Injection of In Situ Forming Alginate Hydrogel Reverses Left Ventricular Remodeling After Myocardial Infarction in Swine

ObjectivesThis study sought to determine whether alginate biomaterial can be delivered effectively into the infarcted myocardium by intracoronary injection to prevent left ventricular (LV) remodeling early after myocardial infarction (MI).BackgroundAlthough injectable biomaterials can improve infarct healing and repair, the feasibility and effectiveness of intracoronary injection have not been studied.MethodsWe prepared a calcium cross-linked alginate solution that undergoes liquid to gel phase transition after deposition in infarcted myocardium. Anterior MI was induced in swine by transient balloon occlusion of left anterior descending coronary artery. At 4 days after MI, either alginate solution (2 or 4 ml) or saline was injected selectively into the infarct-related coronary artery. An additional group (n = 19) was treated with incremental volumes of biomaterial (1, 2, and 4 ml) or 2 ml saline and underwent serial echocardiography studies.ResultsExamination of hearts harvested after injection showed that the alginate crossed the infarcted leaky vessels and was deposited as hydrogel in the infarcted tissue. At 60 days, control swine experienced an increase in left ventricular (LV) diastolic area by 44%, LV systolic area by 45%, and LV mass by 35%. In contrast, intracoronary injection of alginate (2 and 4 ml) prevented and even reversed LV enlargement (p < 0.01). Post-mortem analysis showed that the biomaterial (2 ml) increased scar thickness by 53% compared with control (2.9 ± 0.1 mm vs. 1.9 ± 0.3 mm; p < 0.01) and was replaced by myofibroblasts and collagen.ConclusionsIntracoronary injection of alginate biomaterial is feasible, safe, and effective. Our findings suggest a new percutaneous intervention to improve infarct repair and prevent adverse remodeling after reperfused MI