title: Forecasting pulsatory motion for non-invasive cardiac radiosurgery: an analysis of algorithms from respiratory motion prediction.
abstract: OBJECTIVE
  Recently, radiosurgical treatment of cardiac arrhythmia, especially atrial fibrillation, has been proposed. Using the CyberKnife, focussed radiation will be used to create ablation lines on the beating heart to block unwanted electrical activity. Since this procedure requires high accuracy, the inevitable latency of the system (i.e., the robotic manipulator following the motion of the heart) has to be compensated for.
  
  
  METHODS
  We examine the applicability of prediction algorithms developed for respiratory motion prediction to the prediction of pulsatory motion. We evaluated the MULIN, nLMS, wLMS, SVRpred and EKF algorithms. The test data used has been recorded using external infrared position sensors, 3D ultrasound and the NavX catheter systems.
  
  
  RESULTS
  With this data, we have shown that the error from latency can be reduced by at least 10 and as much as 75% (44% average), depending on the type of signal. It has also been shown that, although the SVRpred algorithm was successful in most cases, it was outperformed by the simple nLMS algorithm, the EKF or the wLMS algorithm in a number of cases.
  
  
  CONCLUSIONS
  We have shown that prediction of cardiac motion is possible and that the algorithms known from respiratory motion prediction are applicable. Since pulsation is more regular than respiration, more research will have to be done to improve frequency-tracking algorithms, like the EKF method, which performed better than expected from their behaviour on respiratory motion traces.
authors.affiliation: Institute for Robotics and Cognitive Systems, University of Lübeck, Ratzeburger Allee 160, Lübeck 23538, Germany. ernst@rob.uni-luebeck.de
authors.forename: Floris
authors.initials: F
authors.lastname: Ernst
authors.forename: Ralf
authors.initials: R
authors.lastname: Bruder
authors.forename: Alexander
authors.initials: A
authors.lastname: Schlaefer
authors.forename: Achim
authors.initials: A
authors.lastname: Schweikard
mesh_terms: D000328:Adult; D000465:Algorithms; D001281:Atrial Fibrillation / Q000503:physiopathology / Q000601:surgery*; D005544:Forecasting; D006801:Humans; D008297:Male; D011237:Predictive Value of Tests; D016634:Radiosurgery / Q000379:methods*; D012016:Reference Values; D015656:Respiratory Mechanics / Q000502:physiology*; D012371:Robotics; D025321:Surgery, Computer-Assisted / Q000379:methods*; D055815:Young Adult