• Peng Wang and Orhan Unal.
• Medical Physics, University of Wisconsin - Madison, Wisconsin, USA.
• J Magn Reson Imaging. 2015 Mar 1; 41 (3): 851-7.

PurposeTo develop and evaluate a real-time proton resonant frequency (PRF) based MR thermometry method with a novel motion compensation technique, using linear phase model and active tracking coils.Materials And MethodsA 6F catheter with multiple tracking coils and radiofrequency (RF) ablation tip was built for ex vivo experiments using excised bovine liver on a 1.5 Tesla scanner. A real-time MR acquisition scheme with interleaved active catheter tracking and multislice imaging was implemented. To evaluate the proposed method, in-plane periodic linear motion and through-plane irregular motion were induced by the rocker capability of the scanner and hand, respectively. Real-time temperature maps of the tissue undergoing a 2-min RF ablation cycle were obtained and used to compare the performance of the proposed method with that of the multi-baseline method.ResultsThe temporal window achieved per acquisition of one slice and catheter tracking is ∼380 ms. The standard deviations of tracking errors are less than 1 mm for both irregular and periodic motions in x-y plane. The measurements at the heated and unheated regions demonstrate that the proposed thermometry method perform equally well for both in-plane and through-plane motion while maintaining a similar accuracy (σ = 1.10 versus 1.04°C) compared with the conventional multi-baseline method.ConclusionThe new MR thermometry method using catheter-based tracking coils and linear phase model for motion compensation and phase correction is promising and may offer reliable MR thermometry for real-time MRI-guided thermal therapies.© 2014 Wiley Periodicals, Inc.

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