title: Parallel imaging enhanced MR colonography using a phantom model.
abstract: OBJECTIVE
  To compare various Array Spatial and Sensitivity Encoding Technique (ASSET)-enhanced T2W SSFSE (single shot fast spin echo) and T1-weighted (T1W) 3D SPGR (spoiled gradient recalled echo) sequences for polyp detection and image quality at MR colonography (MRC) in a phantom model. Limitations of MRC using standard 3D SPGR T1W imaging include the long breath-hold required to cover the entire colon within one acquisition and the relatively low spatial resolution due to the long acquisition time. Parallel imaging using ASSET-enhanced T2W SSFSE and 3D T1W SPGR imaging results in much shorter imaging times, which allows for increased spatial resolution.
  
  
  METHODS
  Using two porcine colon phantoms each with eight simulated 3-10-mm "polyps," baseline reference sequences acquired without ASSET (6-mm slices and readout bandwidth [BW] 62 kHz) were compared with 11 SSFSE and 8 SPGR sequences acquired with 2-fold ASSET acceleration. ASSET-enhanced SSFSE and SPGR sequences comprised BW/matrix combinations ranging from 20-62 kHz/256-352x256, respectively, with slice thicknesses adjusted from 3.0 to 4.5 mm to maintain a 23-26-second acquisition time and 30 cm slab thickness. Two experienced radiologists viewed the datasets in a randomized, blinded fashion.
  
  
  RESULTS
  Compared to reference sequences, ASSET-enhanced SSFSE and SPGR sequences facilitated better polyp detection and had similar overall image quality and per-phantom specificity. The two best ASSET-enhanced SSFSE (3 and 4.5 mm slices, each with BW of 62.5 kHz and 352x256 matrices) and three best ASSET-enhanced SPGR BW/slice thickness/matrix combinations of 31 kHz/4.4 msec/192x256; 62/3.4/192x256; and 62/4.0/192x256, respectively, permitted detection of all polyps>or=5 mm.
  
  
  CONCLUSIONS
  Parallel imaging using ASSET-enhanced T2W SSFSE and T1W 3D SPGR improves the ability to detect significant colon polyps in an MRC phantom model.
authors.affiliation: Department of Radiology, Beaumont Hospital, Dublin, Ireland. mmorrin@rcsi.ie
authors.forename: Martina M
authors.initials: MM
authors.lastname: Morrin
authors.forename: Ivan
authors.initials: I
authors.lastname: Pedrosa
authors.forename: Charles A
authors.initials: CA
authors.lastname: McKenzie
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Farrell
authors.forename: Nicolas
authors.initials: N
authors.lastname: Bloch
authors.forename: Stephanie
authors.initials: S
authors.lastname: Solazzo
authors.forename: Long
authors.initials: L
authors.lastname: Ngo
authors.forename: Shraga N
authors.initials: SN
authors.lastname: Goldberg
authors.forename: Neil M
authors.initials: NM
authors.lastname: Rofsky
mesh_terms: D000465:Algorithms; D000818:Animals; D003106:Colon / Q000473:pathology*; D003111:Colonic Polyps / Q000473:pathology*; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D010363:Pattern Recognition, Automated / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D013552:Swine