title: PRFS-based MR thermometry versus an alternative T1 magnitude method--comparative performance predicting thermally induced necrosis in hepatic tumor ablation.
abstract: OBJECTIVE
  To compare the accuracy of a semi-quantitative proton resonance frequency shift (PRFS) thermal mapping interface and an alternative qualitative T1 thermometry model in predicting tissue necrosis in an established routine setting of MRI-guided laser ablation in the human liver.
  
  
  METHODS
  34 cases of PRFS-guided (GRE) laser ablation were retrospectively matched with 34 cases from an earlier patient population of 73 individuals being monitored through T1 magnitude image evaluation (FLASH 2D). The model-specific real-time estimation of necrotizing thermal impact (above 54 °C zone and T1 signal loss, respectively) was correlated in size with the resulting necrosis as shown by lack of enhancement on the first-day contrast exam (T1). Matched groups were compared using the Mann-Whitney test.
  
  
  RESULTS
  Online PRFS guidance was available in 33 of 34 cases. Positive size correlation between calculated impact zone and contrast defect at first day was evident in both groups (p < 0.0004). The predictive error estimating necrosis was median 21% (range 1 %-52%) in the PRFS group and 61 % (range 22-84%) in the T1 magnitude group. Differences in estimating lethal impact were significant (p = 0.004), whereas the real extent of therapy-induced necrosis showed no significant difference (p > 0.28) between the two groups.
  
  
  CONCLUSIONS
  PRFS thermometry is feasible in a clinical setting of thermal hepatic tumor ablation. As an interference-free MR-tool for online therapy monitoring its accuracy to predict tissue necrosis is superior to a competing model of thermally induced alteration of the T1 magnitude signal.
authors.affiliation: Institute of Diagnostic Radiology and Neuroradiology, University Medicine Greifswald, Greifswald, Mecklenburg-Vorpommern, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Rosenberg
authors.forename: Antje
authors.initials: A
authors.lastname: Kickhefel
authors.forename: Birger
authors.initials: B
authors.lastname: Mensel
authors.forename: Tilman
authors.initials: T
authors.lastname: Pickartz
authors.forename: Ralf
authors.initials: R
authors.lastname: Puls
authors.forename: Joerg
authors.initials: J
authors.lastname: Roland
authors.forename: Norbert
authors.initials: N
authors.lastname: Hosten
mesh_terms: D001943:Breast Neoplasms / Q000556:secondary; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D053685:Laser Therapy / Q000379:methods*; D008113:Liver Neoplasms / Q000473:pathology* / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008297:Male; D009336:Necrosis; D011522:Protons; D012189:Retrospective Studies; D025321:Surgery, Computer-Assisted / Q000379:methods*; D013696:Temperature; D062125:Thermometry / Q000379:methods*; D016896:Treatment Outcome
chemical_list: D011522:Protons