title: A body-sized phantom for evaluation of diffusion-weighted MRI data using conventional, readout-segmented, and zoomed echo-planar sequences.
abstract: BACKGROUND
  Abdominal diffusion-weighted imaging (DWI) has been rapidly increasing during the last few years. For the evaluation of new DWI techniques, the development of suitable phantoms and quality assurance methods is important.
  
  
  OBJECTIVE
  To construct a body-diameter phantom for abdominal DWI and study the impact of different acquisition options on image quality.
  
  
  METHODS
  A phantom with a diameter of 31 cm and a volume of 26 L was constructed, containing four samples representing a clinically relevant range of apparent diffusion coefficient (ADC) values. Measurements were carried out on 1.5T and 3.0T MRI systems using conventional echo-planar imaging (EPI), readout-segmented EPI, and zoomed EPI (3.0T) sequences. The effects of parallel imaging, coil intensity normalization, and patient-specific B1 shim (3.0T) were also examined. ADC values and signal-to-noise ratios of the samples were measured, and the level of artifacts was visually evaluated.
  
  
  RESULTS
  The agreement of ADC values between different acquisition options was generally good, but higher values (by 0.07 × 10(-3) mm(2)/s on the average) with readout-segmented EPI as well as ADC variations of approximately 0.1 × 10(-3) mm(2)/s in slice direction were observed. The image artifacts were reduced by using patient-specific B1 shim, readout-segmented EPI, or zoomed EPI.
  
  
  CONCLUSIONS
  The body-sized phantom demonstrated well the expected image artifacts in DWI with large field of view. The use of patient-specific B1 shim, readout-segmented EPI, or zoomed EPI improved image quality of DWI in this study.
authors.affiliation: HUS Medical Imaging Center, Radiology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland Department of Physics, University of Helsinki, Helsinki, Finland toni.ihalainen@hus.fi.
authors.forename: Toni
authors.initials: T
authors.lastname: Ihalainen
authors.affiliation: HUS Medical Imaging Center, Radiology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland Department of Physics, University of Helsinki, Helsinki, Finland.
authors.forename: Linda
authors.initials: L
authors.lastname: Kuusela
authors.affiliation: Department of Chemistry, University of Helsinki, Helsinki, Finland.
authors.forename: Maiju
authors.initials: M
authors.lastname: Soikkeli
authors.affiliation: HUS Medical Imaging Center, Radiology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
authors.forename: Eila
authors.initials: E
authors.lastname: Lantto
authors.affiliation: HUS Medical Imaging Center, Radiology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
authors.forename: Ali
authors.initials: A
authors.lastname: Ovissi
authors.affiliation: HUS Medical Imaging Center, Clinical Physiology and Nuclear Medicine, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
authors.forename: Outi
authors.initials: O
authors.lastname: Sipilä
mesh_terms: D000005:Abdomen / Q000000981:diagnostic imaging*; D016477:Artifacts; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D017352:Echo-Planar Imaging / Q000379:methods; D004867:Equipment Design; D006801:Humans; D019047:Phantoms, Imaging; D059629:Signal-To-Noise Ratio
keywords: Magnetic resonance (MR) diffusion/perfusion; imaging sequences; quality assurance/quality control (QA/QC)