Motion correction in MR thermometry of abdominal organs: A comparison of the referenceless vs. the multibaseline approach

Reliable temperature and thermal‐dose measurements using proton resonance frequency shift‐based magnetic resonance (MR) thermometry for MR‐guided ablation of abdominal organs require a robust correction of artefacts induced by the target displacement through an inhomogeneous and time‐variant magnetic field. Two correction approaches emerged recently as promising candidates to allow continuous real‐time MR‐thermometry under free‐breathing conditions: The multibaseline correction method, which relies on a pre‐recorded correction table allowing to correct for periodic phase changes, and the referenceless method, which depends on a background phase estimation in the target area based on the assumption of a smooth spatial variation of the phase across the organ. This study combines both methods with real‐time in‐plane motion correction to permit both temperature and thermal‐dose calculations on the fly. Subsequently, the practical aspects of both methods are compared in two application scenarios, a radio frequency‐ablation and a high‐intensity focused ultrasound ablation. A hybrid approach is presented that exploits the strong points of both methods, allowing accurate and precise proton resonance frequency‐thermometry measurements during periodical displacement, even in the presence of spontaneous motion and strong susceptibility variations in the target area. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.