title: Impact of field strength and RF excitation on abdominal diffusion-weighted magnetic resonance imaging.
abstract: OBJECTIVE
  To retrospectively and prospectively compare diffusion-weighted (DW) images in the abdomen in a 1.5T system and 3.0T systems with and without two-channel functionality for B1 shimming.
  
  
  METHODS
  DW images of the abdomen were obtained on 1.5T and 3.0T (with and without two-channel functionality for B1 shimming) scanners on 150 patients (retrospective study population) and 10 volunteers (prospective study population). Eight regions were selected for clinical significance or artifact susceptibility (at higher field strengths). Objective grading quantified signal-to-noise ratio (SNR), and subjective evaluation qualified image quality, ghosting artifacts, and diagnostic value. Statistical significance was calculated using χ(2) tests (categorical variables) and independent two-sided t tests or Mann-Whitney U tests (continuous variables).
  
  
  RESULTS
  The 3.0T using dual-source parallel transmit (dpTX 3.0T) provided the significantly highest SNRs in nearly all regions. In regions susceptible to artifacts at higher field strengths (left lobe of liver, head of pancreas), the SNR was better or similar to the 1.5T system. Subjectively, both dpTX 3.0T and 1.5T systems provided higher image quality, diagnostic value, and less ghosting artifact (P < 0.01, most values) compared to the 3.0T system without dual-source parallel transmit (non-dpTX 3.0T).
  
  
  CONCLUSIONS
  The dpTX 3.0T scanner provided the highest SNR. Its image quality, lack of ghosting, and diagnostic value were equal to or outperformed most currently used systems.
authors.affiliation: Philipp Riffel, Raghuram K Rao, Stefan Haneder, Mathias Meyer, Stefan O Schoenberg, Henrik J Michaely, Department of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Medical Faculty Mannheim-Heidelberg University, D-68167 Mannheim, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Riffel
authors.forename: Raghuram K
authors.initials: RK
authors.lastname: Rao
authors.forename: Stefan
authors.initials: S
authors.lastname: Haneder
authors.forename: Mathias
authors.initials: M
authors.lastname: Meyer
authors.forename: Stefan O
authors.initials: SO
authors.lastname: Schoenberg
authors.forename: Henrik J
authors.initials: HJ
authors.lastname: Michaely
keywords: 3.0T; Abdominal imaging; Diffusion weighted; Radiofrequency excitation; Signal-to-noise ratio