title: Projection-based estimation and nonuniformity correction of sensitivity profiles in phased-array surface coils.
abstract: OBJECTIVE
  To develop a novel approach for calculating the accurate sensitivity profiles of phased-array coils, resulting in correction of nonuniform intensity in parallel MRI.
  
  
  METHODS
  The proposed intensity-correction method estimates the accurate sensitivity profile of each channel of the phased-array coil. The sensitivity profile is estimated by fitting a nonlinear curve to every projection view through the imaged object. The nonlinear curve-fitting efficiently obtains the low-frequency sensitivity profile by eliminating the high-frequency image contents. Filtered back-projection (FBP) is then used to compute the estimates of the sensitivity profile of each channel. The method was applied to both phantom and brain images acquired from the phased-array coil.
  
  
  RESULTS
  Intensity-corrected images from the proposed method had more uniform intensity than those obtained by the commonly used sum-of-squares (SOS) approach. With the use of the proposed correction method, the intensity variation was reduced to 6.1% from 13.1% of the SOS. When the proposed approach was applied to the computation of the sensitivity maps during sensitivity encoding (SENSE) reconstruction, it outperformed the SOS approach in terms of the reconstructed image uniformity.
  
  
  CONCLUSIONS
  The proposed method is more effective at correcting the intensity nonuniformity of phased-array surface-coil images than the conventional SOS method. In addition, the method was shown to be resilient to noise and was successfully applied for image reconstruction in parallel imaging.
authors.affiliation: Department of Electrical Engineering, Korea Advanced Institute of Science and Technology, Daejeon, South Korea.
authors.forename: Sungdae
authors.initials: S
authors.lastname: Yun
authors.forename: Walid E
authors.initials: WE
authors.lastname: Kyriakos
authors.forename: Jun-Young
authors.initials: JY
authors.lastname: Chung
authors.forename: Yeji
authors.initials: Y
authors.lastname: Han
authors.forename: Seung-Schik
authors.initials: SS
authors.lastname: Yoo
authors.forename: Hyunwook
authors.initials: H
authors.lastname: Park
mesh_terms: D000465:Algorithms; D001921:Brain / Q000033:anatomy & histology*; D005240:Feasibility Studies; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity