title: Computationally efficient noninvasive cardiac activation time imaging.
abstract: OBJECTIVE
  The computer model-based computation of the cardiac activation sequence in humans has been recently subject of successful clinical validation. This method is of potential interest for guiding ablation therapy of arrhythmogenic substrates. However, computation times of almost an hour are unattractive in a clinical setting. Thus, the objective is the development of a method which performs the computation in a few minutes run time.
  
  
  METHODS
  The computationally most expensive part is the product of the lead field matrix with a matrix containing the source pattern on the cardiac surface. The particular biophysical properties of both matrices are used for speeding up this operation by more than an order of magnitude. A conjugate gradient optimizer was developed using C++ for computing the activation map.
  
  
  RESULTS
  The software was tested on synthetic and clinical data. The increase in speed with respect to the previously used Fortran 77 implementation was a factor of 30 at a comparable quality of the results. As an additional finding the coupled regularization strategy, originally introduced for saving computation time, also reduced the sensitivity of the method to the choice of the regularization parameter.
  
  
  CONCLUSIONS
  As it was shown for data from a WPWpatient the developed software can deliver diagnostically valuable information at a much shorter span of time than current clinical routine methods. Its main application could be the localization of focal arrhythmogenic substrates.
authors.affiliation: Institute for Biomedical Signal Processing and Imaging, University for Health Sciences, Medical Informatics and Technology (UMIT), Innsbruck, Austria. gerald.fischer@umit.at
authors.forename: G
authors.initials: G
authors.lastname: Fischer
authors.forename: B
authors.initials: B
authors.lastname: Pfeifer
authors.forename: M
authors.initials: M
authors.lastname: Seger
authors.forename: C
authors.initials: C
authors.lastname: Hintermüller
authors.forename: F
authors.initials: F
authors.lastname: Hanser
authors.forename: R
authors.initials: R
authors.lastname: Modre
authors.forename: B
authors.initials: B
authors.lastname: Tilg
authors.forename: T
authors.initials: T
authors.lastname: Trieb
authors.forename: C
authors.initials: C
authors.lastname: Kremser
authors.forename: F X
authors.initials: FX
authors.lastname: Roithinger
authors.forename: F
authors.initials: F
authors.lastname: Hintringer
mesh_terms: D001145:Arrhythmias, Cardiac / Q000601:surgery; D001317:Austria; D017115:Catheter Ablation; D003198:Computer Simulation; D022062:Electrophysiologic Techniques, Cardiac; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D012984:Software; D013997:Time Factors