Atlas-based motion correction for online MR temperature mapping

Magnetic resonance (MR) temperature mapping can be used to monitor temperature changes in minimally invasive thermal therapies during the procedure. However, organs displacements due to physiological activity (heart and respiration) may induce important artifacts on apparent temperature maps. This paper presents a new method for motion quantification and correction in such MR images, in order to improve the precision of temperature estimation using the proton resonance frequency (PRF) shift. The PRF shift technique gives an estimate of the relative temperature variation, comparing contrast between dynamically acquired images and a reference data sets. The correction method described in this paper consists of two steps: a motion atlas is initially computed in a preparation phase; during the intervention, the appropriate reference image is chosen from the atlas, allowing correct computation of the temperature map despite tissue motion. This method can be applied to any type of image sequences and is not restricted to MR images.