Jens Haueisen

Publications (124) View all

• Article: Repeatability of Autofluorescence Lifetime Imaging at the Human Fundus in Healthy Volunteers.

  Matthias Klemm, Alexander Dietzel, Jens Haueisen, Edgar Nagel, Martin Hammer, Dietrich Schweitzer
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  ABSTRACT: Abstract Purpose: We aim to evaluate the repeatability of a new fluorescence lifetime imaging (FLIM) technique which measures time-resolved autofluorescence to assess metabolism of the retina. Materials and methods: We performed FLIM with two spectral channels (channel 1: 490-560 nm and channel 2: 560-700 nm) on 10 healthy volunteers, with 10 replicates per volunteer. From the 30° fundus FLIM images, we selected three regions: the fovea, the optic disc and the papillo-macular bundle. For each channel in these regions, we determined an average multi-exponential approximation with three components, and the six resulting parameters, α1-α3 (amplitudes) and τ1-τ3 (fluorescence lifetimes), were analyzed in terms of the coefficient of variation (CV). Results: Repeatability was highest in the papillo-macular bundle, followed by the fovea and the optic disc. Repeatability was higher in channel 1 (mean CV of 7.9%) than in channel 2 (mean CV of 17.7%). The average CV for the diagnostically most relevant channel 1 and the most relevant parameters was as follows: τ1 (5.5%) and τ2 (4.7%) in the papillo-macular bundle, and τ1 (6.8%) and τ2 (6.9%) in the fovea. Conclusions: We demonstrated repeatability of FLIM measurement results within acceptable ranges of variation. Based on the detailed coefficients of variation, we derived recommendations for parameter ranges suitable for diagnostic applications.
  Current eye research 03/2013; · 1.51 Impact Factor
• Source

  Available from: Silvia Comani

  Article: Early detection of coronary artery disease in patients studied with magnetocardiography: An automatic classification system based on signal entropy.

  Martin Steinisch, Paul R Torke, Jens Haueisen, Birgit Hailer, Dietrich Grönemeyer, Peter Van Leeuwen, Silvia Comani
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  ABSTRACT: We propose an automatic system for the classification of coronary artery disease (CAD) based on entropy measures of MCG recordings. Ten patients with coronary artery narrowing≥or≤50% were categorized by a multilayer perceptron (MLP) neural network based on Linear Discriminant Analysis (LDA). Best results were obtained with MCG at rest: 99% sensitivity, 97% specificity, 98% accuracy, 96% and 99% positive and negative predictive values for single heartbeats. At patient level, these results correspond to a correct classification of all patients. The classifier's suitability to detect CAD-induced changes on the MCG at rest was validated with surrogate data.
  Computers in biology and medicine 12/2012; · 1.27 Impact Factor
• Source

  Available from: Paolo Gargiulo

  Article: 3D segmented model of head for modelling electrical activity ofbrain

  Egill A Friðgeirsson,, Paolo Gargiulo,, Ceon Ramon,, Jens Haueisen
  Basic and applied myology: BAM 12/2012; 22((1&2)):57-60.
• Article: Adapting source grid parameters to improve the condition of the magnetostatic linear inverse problem of estimating nanoparticle distributions.

  Roland Eichardt, Daniel Baumgarten, Bojana Petković, Frank Wiekhorst, Lutz Trahms, Jens Haueisen
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  ABSTRACT: The problem of estimating magnetic nanoparticle distributions from magnetorelaxometric measurements is addressed here. The objective of this work was to identify source grid parameters that provide a good condition for the related linear inverse problem. The parameters investigated here were the number of sources, the extension of the source grid, and the source direction. A new measure of the condition, the ratio between the largest and mean singular value of the lead field matrix, is proposed. Our results indicated that the source grids should be larger than the sensor area. The sources and, consequently, the magnetic excitation field, should be directed toward the Z-direction. For underdetermined linear inverse problems, such as in our application, the number of sources affects the condition to a relatively small degree. Overdetermined magnetostatic linear inverse problems, however, benefit from a reduction in the number of sources, which considerably improves the condition. The adapted source grids proposed here were used to estimate the magnetostatic dipole from simulated data; the L2-norm, residual, and distances between the estimated and simulated sources were significantly reduced.
  Medical & Biological Engineering 09/2012; 50(10):1081-9. · 1.76 Impact Factor
• Conference Proceeding: Effects of the Source Direction Constraint on the Condition of the Magnetostatic Lead Field Matrix

  Roland Eichardt, Uwe Graichen, Matti Stenroos, Jens Haueisen
  Proceedings of the 12th International Workshop on Optimization and Inverse Problems in Electromagnetism, Ghent, Belgium; 09/2012