title: Parallel-transmit-accelerated spatially-selective excitation MRI for reduced-FOV diffusion-weighted-imaging of the pancreas.
abstract: OBJECTIVE
  To find out whether the use of accelerated 2D-selective parallel-transmit excitation MRI for diffusion-weighted EPI (pTX-EPI) offers advantages over conventional single-shot EPI (c-EPI) with respect to different aspects of image quality in the MRI of the pancreas.
  
  
  METHODS
  The MRI examinations of 33 consecutive patients were evaluated in this prospective and IRB-approved study. PTX-EPI was performed with a reduced (zoomed) FOV of 230 × 118 mm(2). The 2D-RF pulse of pTX-EPI was accelerated, i.e. shortened by a factor of 1.7 (pTX-acceleration factor). C-EPI used a full-FOV of 380 × 285 mm(2). In a qualitative analysis, two experienced readers evaluated 3 different aspects of image quality on 3- to 5-point Likert scales. Additionally, apparent diffusion coefficients (ADCs) were determined in both c-EPI and pTX-EPI in normal-appearing pancreatic tissue using regions of interests (ROIs). Mean ADC values and standard deviations were compared between the two techniques.
  
  
  RESULTS
  The reduced-FOV pTX-EPI was superior to c-EPI with respect to overall image quality (p<0.0001) and identifiability of the pancreatic ducts (p<0.01). Artifacts were significantly less severe in pTX-EPI (p<0.01). The mean ADC values of c-EPI (1.29 ± 0.19 × 10(-3)mm(2)/s) and pTX-EPI (1.27 ± 0.17 × 10(-3)mm(2)/s) did not differ significantly between the two techniques (p=0.44). The variation within the ROIs as measured by the standard deviation was significantly lower in pTX-EPI (0.095 × 10(-3)mm(2)/s) than in c-EPI (0.135 × 10(-3)mm(2)/s), p<0.05.
  
  
  CONCLUSIONS
  PTX-accelerated EPI with spatially-selective excitation and reduced FOV leads to substantial improvements in DWI of the pancreas with respect to different aspects of image quality without significantly influencing the ADC values.
authors.affiliation: Department of Clinical Radiology, Ludwig-Maximilians-University of Munich Hospitals, Munich, Germany. Electronic address: kolja.thierfelder@med.uni-muenchen.de.
authors.forename: Kolja M
authors.initials: KM
authors.lastname: Thierfelder
authors.affiliation: Department of Clinical Radiology, Ludwig-Maximilians-University of Munich Hospitals, Munich, Germany.
authors.forename: Wieland H
authors.initials: WH
authors.lastname: Sommer
authors.affiliation: Josef Lissner Laboratory for Biomedical Imaging, Department of Clinical Radiology, Ludwig-Maximilians-University of Munich Hospitals, Munich, Germany.
authors.forename: Olaf
authors.initials: O
authors.lastname: Dietrich
authors.affiliation: Department of Clinical Radiology, Ludwig-Maximilians-University of Munich Hospitals, Munich, Germany.
authors.forename: Felix G
authors.initials: FG
authors.lastname: Meinel
authors.affiliation: Department of Clinical Radiology, Ludwig-Maximilians-University of Munich Hospitals, Munich, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Theisen
authors.affiliation: Department of Clinical Radiology, Ludwig-Maximilians-University of Munich Hospitals, Munich, Germany.
authors.forename: Philipp M
authors.initials: PM
authors.lastname: Paprottka
authors.affiliation: Department of Clinical Radiology, Ludwig-Maximilians-University of Munich Hospitals, Munich, Germany.
authors.forename: Frederik F
authors.initials: FF
authors.lastname: Strobl
authors.affiliation: Siemens AG, Healthcare Sector, Erlangen, Germany.
authors.forename: Josef
authors.initials: J
authors.lastname: Pfeuffer
authors.affiliation: Department of Clinical Radiology, Ludwig-Maximilians-University of Munich Hospitals, Munich, Germany.
authors.forename: Maximilian F
authors.initials: MF
authors.lastname: Reiser
authors.affiliation: Department of Clinical Radiology, Ludwig-Maximilians-University of Munich Hospitals, Munich, Germany; Department of Diagnostic and Interventional Radiology, University Hospital Tuebingen, Tuebingen, Germany.
authors.forename: Konstantin
authors.initials: K
authors.lastname: Nikolaou
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016477:Artifacts; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D017352:Echo-Planar Imaging; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010182:Pancreatic Diseases / Q000175:diagnosis*; D011446:Prospective Studies
keywords: Diffusion-weighted imaging; Magnetic resonance imaging; Pancreatic imaging; Parallel-transmit; pTX-acceleration