title: Regularized antenna profile adaptation in online hyperthermia treatment.
abstract: OBJECTIVE
  Online optimization of annular-phased-array hyperthermia (HT) is based on planning tools and magnetic resonance (MR) thermometry. Until now, the method has been validated in phantoms. Further developments and extensions are required for clinical purposes. In particular, the problem of deducing the electric field distribution inside the patient from MR thermometry is ill-posed, which leads to an amplification of measurement errors. A method to overcome this difficulty is proposed.
  
  
  METHODS
  The authors utilized a regularized Gauss-Newton algorithm with a fast bioheat transfer equation (BHTE) approximation to identify the field parameters. To evaluate the method, simulations with patient models are conducted and a treatment data set obtained from a heat treatment performed in the hybrid HT-MR system at the Charité Medical School is used to visualize the error amplification.
  
  
  RESULTS
  The regularization leads to a significantly improved accuracy of the predicted electric fields and temperatures compared to an unregularized approach. The BHTE approximation enables highly accurate temperature predictions in real-time.
  
  
  CONCLUSIONS
  Regularization proves to be necessary to identify electromagnetic field parameters. The proposed method is able to reproduce measurements without overfitting to the noise in the MR measurements and results in an improved treatment planning.
authors.affiliation: Department Numerical Analysis and Modelling, Zuse Institute Berlin, Takustrasse 7, 14195 Berlin, Germany.
authors.forename: Maximilian
authors.initials: M
authors.lastname: Ranneberg
authors.forename: Martin
authors.initials: M
authors.lastname: Weiser
authors.forename: Mirko
authors.initials: M
authors.lastname: Weihrauch
authors.forename: Volker
authors.initials: V
authors.lastname: Budach
authors.forename: Johanna
authors.initials: J
authors.lastname: Gellermann
authors.forename: Peter
authors.initials: P
authors.lastname: Wust
mesh_terms: D000465:Algorithms; D055592:Biophysical Phenomena; D006801:Humans; D006979:Hyperthermia, Induced / Q000706:statistics & numerical data*; D016018:Least-Squares Analysis; D009682:Magnetic Resonance Spectroscopy; D008954:Models, Biological; D009369:Neoplasms / Q000628:therapy; D017711:Nonlinear Dynamics; D009862:Online Systems; D013696:Temperature