Cardiac motion in diffusion-weighted MRI of the liver: Artifact and a method of correction

Abstract

Purpose: To characterize cardiac motion artifacts in the liver and assess the use of a postprocessing method to mitigate these artifacts in repeat measurements. Materials and Methods: Three subjects underwent breathhold diffusion-weighted (DW) scans consisting of 25 repetitions for three b-values (0, 500, 1000 sec/mm2). Statistical maps computed from these repetitions were used to assess the distribution and behavior of cardiac motion artifacts in the liver. An objective postprocessing method to reduce the artifacts was compared with radiologist-defined gold standards. Results: Signal dropout is pronounced in areas proximal to the heart, such as the left lobe, but also present in the right lobe and in distal liver segments. The dropout worsens with b-value and leads to overestimation of the diffusivity. By reference to a radiologist-defined gold standard, a postprocessing correction method is shown to reduce cardiac motion artifact. Conclusion: Cardiac motion leads to significant artifacts in liver DW imaging; we propose a postprocessing method that may be used to mitigate the artifact and is advantageous to standard signal averaging in acquisitions with multiple repetitions. © 2011 Wiley Periodicals, Inc.