title: Selection and evaluation of optimal two-dimensional CAIPIRINHA kernels applied to time-resolved three-dimensional CE-MRA.
abstract: OBJECTIVE
  To develop and validate a method for choosing the optimal two-dimensional CAIPIRINHA kernel for subtraction contrast-enhanced MR angiography (CE-MRA) and estimate the degree of image quality improvement versus that of some reference acceleration parameter set at R ≥ 8.
  
  
  METHODS
  A metric based on patient-specific coil calibration information was defined for evaluating optimality of CAIPIRINHA kernels as applied to subtraction CE-MRA. Evaluation in retrospective studies using archived coil calibration data from abdomen, calf, foot, and hand CE-MRA exams was accomplished with an evaluation metric comparing the geometry factor (g-factor) histograms. Prospective calf, foot, and hand CE-MRA studies were evaluated with vessel signal-to-noise ratio (SNR).
  
  
  RESULTS
  Retrospective studies show g-factor improvement for the selected CAIPIRINHA kernels was significant in the feet, moderate in the abdomen, and modest in the calves and hands. Prospective CE-MRA studies using optimal CAIPIRINHA show reduced noise amplification with identical acquisition time in studies of the feet, with minor improvements in the hands and calves.
  
  
  CONCLUSIONS
  A method for selection of the optimal CAIPIRINHA kernel for high (R ≥ 8) acceleration CE-MRA exams given a specific patient and receiver array was demonstrated. CAIPIRINHA optimization appears valuable in accelerated CE-MRA of the feet and to a lesser extent in the abdomen.
authors.affiliation: Department of Radiology, MR Research Laboratory, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Paul T
authors.initials: PT
authors.lastname: Weavers
authors.affiliation: Department of Radiology, MR Research Laboratory, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Eric A
authors.initials: EA
authors.lastname: Borisch
authors.affiliation: Department of Radiology, MR Research Laboratory, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Riederer
mesh_terms: D015901:Angiography, Digital Subtraction; D002138:Calibration; D003287:Contrast Media; D005528:Foot / Q000098:blood supply*; D006225:Hand / Q000098:blood supply*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007866:Leg / Q000098:blood supply*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D011446:Prospective Studies; D012189:Retrospective Studies
chemical_list: D003287:Contrast Media
keywords: CAIPIRINHA; acceleration; optimization; parallel imaging