title: A pilot study for clinical feasibility of the near-harmonic 2D referenceless PRFS thermometry in liver under free breathing using MR-guided LITT ablation data.
abstract: OBJECTIVE
  The conventional implementations of proton resonance frequency shift (PRFS) magnetic resonance thermometry (MRT) require the subtraction of single or multiple temporal references, a motion sensitive critical feature. A pilot study was conducted here to investigate the clinical feasibility of near-harmonic two-dimensional (2D) referenceless PRFS MRT, using patient data from MR-guided laser ablation of liver malignancies.
  
  
  METHODS
  PRFS MRT with respiratory-triggered multi-slice gradient-recalled (GRE) acquisition was performed under free breathing in six patients. The precision of the novel referenceless MRT was compared with the reference phase subtraction. Coupling the referenceless MRT with a model-based, real-time compatible regularisation algorithm was also investigated.
  
  
  RESULTS
  The precision of MRT was improved by a factor of 3.3 when using the referenceless method as compared to the reference phase subtraction. The approach combining referenceless PRFS MRT and model-based regularisation yielded an estimated precision of 0.7° to 2.1°C, resulting in millimetre-range agreement between the calculated thermal dose and the 24 h post-treatment unperfused regions in liver.
  
  
  CONCLUSIONS
  The application of the near-harmonic 2D referenceless MRT method was feasible in a clinical scenario of MR-guided laser-induced thermal therapy (LITT) ablation in liver and permitted accurate prediction of the thermal lesion under free breathing in conscious patients, obviating the need for a controlled breathing under general anaesthesia.
authors.affiliation: Diagnostic and Interventional Radiology, Eberhard Karls University, Tübingen, Germany. antje.kickhefel@siemens.com
authors.forename: Antje
authors.initials: A
authors.lastname: Kickhefel
authors.forename: Christian
authors.initials: C
authors.lastname: Rosenberg
authors.forename: Jörg
authors.initials: J
authors.lastname: Roland
authors.forename: Magalie
authors.initials: M
authors.lastname: Viallon
authors.forename: Patrick
authors.initials: P
authors.lastname: Gross
authors.forename: Fritz
authors.initials: F
authors.lastname: Schick
authors.forename: Norbert
authors.initials: N
authors.lastname: Hosten
authors.forename: Rares
authors.initials: R
authors.lastname: Salomir
mesh_terms: D000368:Aged; D001943:Breast Neoplasms / Q000628:therapy; D015179:Colorectal Neoplasms / Q000556:secondary / Q000628:therapy; D005260:Female; D006801:Humans; D006979:Hyperthermia, Induced / Q000379:methods*; D053685:Laser Therapy; D008099:Liver / Q000601:surgery*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D019047:Phantoms, Imaging; D010865:Pilot Projects; D012004:Rectal Neoplasms / Q000628:therapy; D012119:Respiration; D013274:Stomach Neoplasms / Q000628:therapy; D013817:Thermography / Q000379:methods