title: Body MR Imaging: Artifacts, k-Space, and Solutions.
abstract: Body magnetic resonance (MR) imaging is challenging because of the complex interaction of multiple factors, including motion arising from respiration and bowel peristalsis, susceptibility effects secondary to bowel gas, and the need to cover a large field of view. The combination of these factors makes body MR imaging more prone to artifacts, compared with imaging of other anatomic regions. Understanding the basic MR physics underlying artifacts is crucial to recognizing the trade-offs involved in mitigating artifacts and improving image quality. Artifacts can be classified into three main groups: (a) artifacts related to magnetic field imperfections, including the static magnetic field, the radiofrequency (RF) field, and gradient fields; (b) artifacts related to motion; and (c) artifacts arising from methods used to sample the MR signal. Static magnetic field homogeneity is essential for many MR techniques, such as fat saturation and balanced steady-state free precession. Susceptibility effects become more pronounced at higher field strengths and can be ameliorated by using spin-echo sequences when possible, increasing the receiver bandwidth, and aligning the phase-encoding gradient with the strongest susceptibility gradients, among other strategies. Nonuniformities in the RF transmit field, including dielectric effects, can be minimized by applying dielectric pads or imaging at lower field strength. Motion artifacts can be overcome through respiratory synchronization, alternative k-space sampling schemes, and parallel imaging. Aliasing and truncation artifacts derive from limitations in digital sampling of the MR signal and can be rectified by adjusting the sampling parameters. Understanding the causes of artifacts and their possible solutions will enable practitioners of body MR imaging to meet the challenges of novel pulse sequence design, parallel imaging, and increasing field strength.
authors.affiliation: From the Department of Radiology, Massachusetts General Hospital, 55 Fruit St, Boston, MA 02114 (S.Y.H., P.F.H., A.R.G.); Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Mass (S.Y.H., A.R.G.);Department of Radiology, University of Chicago, Chicago, Ill (P.P.); and Siemens Healthcare USA, Malvern, Pa (R.T.S., J.E.K.).
authors.forename: Susie Y
authors.initials: SY
authors.lastname: Huang
authors.affiliation: From the Department of Radiology, Massachusetts General Hospital, 55 Fruit St, Boston, MA 02114 (S.Y.H., P.F.H., A.R.G.); Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Mass (S.Y.H., A.R.G.);Department of Radiology, University of Chicago, Chicago, Ill (P.P.); and Siemens Healthcare USA, Malvern, Pa (R.T.S., J.E.K.).
authors.forename: Ravi T
authors.initials: RT
authors.lastname: Seethamraju
authors.affiliation: From the Department of Radiology, Massachusetts General Hospital, 55 Fruit St, Boston, MA 02114 (S.Y.H., P.F.H., A.R.G.); Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Mass (S.Y.H., A.R.G.);Department of Radiology, University of Chicago, Chicago, Ill (P.P.); and Siemens Healthcare USA, Malvern, Pa (R.T.S., J.E.K.).
authors.forename: Pritesh
authors.initials: P
authors.lastname: Patel
authors.affiliation: From the Department of Radiology, Massachusetts General Hospital, 55 Fruit St, Boston, MA 02114 (S.Y.H., P.F.H., A.R.G.); Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Mass (S.Y.H., A.R.G.);Department of Radiology, University of Chicago, Chicago, Ill (P.P.); and Siemens Healthcare USA, Malvern, Pa (R.T.S., J.E.K.).
authors.forename: Peter F
authors.initials: PF
authors.lastname: Hahn
authors.affiliation: From the Department of Radiology, Massachusetts General Hospital, 55 Fruit St, Boston, MA 02114 (S.Y.H., P.F.H., A.R.G.); Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Mass (S.Y.H., A.R.G.);Department of Radiology, University of Chicago, Chicago, Ill (P.P.); and Siemens Healthcare USA, Malvern, Pa (R.T.S., J.E.K.).
authors.forename: John E
authors.initials: JE
authors.lastname: Kirsch
authors.affiliation: From the Department of Radiology, Massachusetts General Hospital, 55 Fruit St, Boston, MA 02114 (S.Y.H., P.F.H., A.R.G.); Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Mass (S.Y.H., A.R.G.);Department of Radiology, University of Chicago, Chicago, Ill (P.P.); and Siemens Healthcare USA, Malvern, Pa (R.T.S., J.E.K.).
authors.forename: Alexander R
authors.initials: AR
authors.lastname: Guimaraes
mesh_terms: D000273:Adipose Tissue / Q000473:pathology; D000703:Analog-Digital Conversion; D016477:Artifacts; D017352:Echo-Planar Imaging / Q000295:instrumentation / Q000379:methods; D004867:Equipment Design; D004868:Equipment Failure; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation / Q000379:methods*; D008280:Magnetics; D009038:Motion; D012680:Sensitivity and Specificity; D014781:Viscera / Q000473:pathology