title: Influence of temporal regularization and radial undersampling factor on compressed sensing reconstruction in dynamic contrast enhanced MRI of the breast.
abstract: BACKGROUND
  To evaluate the influence of temporal sparsity regularization and radial undersampling on compressed sensing reconstruction of dynamic contrast-enhanced (DCE) MRI, using the iterative Golden-angle RAdial Sparse Parallel (iGRASP) MRI technique in the setting of breast cancer evaluation.
  
  
  METHODS
  DCE-MRI examinations of the breast (n = 7) were conducted using iGRASP at 3 Tesla. Images were reconstructed with five different radial undersampling schemes corresponding to temporal resolutions between 2 and 13.4 s/frame and with four different weights for temporal sparsity regularization (λ = 0.1, 0.5, 2, and 6 times of noise level). Image similarity to time-averaged reference images was assessed by two breast radiologists and using quantitative metrics. Temporal similarity was measured in terms of wash-in slope and contrast kinetic model parameters.
  
  
  RESULTS
  iGRASP images reconstructed with λ = 2 and 5.1 s/frame had significantly (P < 0.05) higher similarity to time-averaged reference images than the images with other reconstruction parameters (mutual information (MI) >5%), in agreement with the assessment of two breast radiologists. Higher undersampling (temporal resolution < 5.1 s/frame) required stronger temporal sparsity regularization (λ ≥ 2) to remove streaking aliasing artifacts (MI > 23% between λ = 2 and 0.5). The difference between the kinetic-model transfer rates of benign and malignant groups decreased as temporal resolution decreased (82% between 2 and 13.4 s/frame).
  
  
  CONCLUSIONS
  This study demonstrates objective spatial and temporal similarity measures can be used to assess the influence of sparsity constraint and undersampling in compressed sensing DCE-MRI and also shows that the iGRASP method provides the flexibility of optimizing these reconstruction parameters in the postprocessing stage using the same acquired data.
authors.affiliation: Center for Advanced Imaging and Innovation and Research (CAI2R) and.|Department of Radiology, Bernard and Irene Schwartz Center for Biomedical Imaging, New York University School of Medicine New York, New York, USA.
authors.forename: Sungheon G
authors.initials: SG
authors.lastname: Kim
authors.affiliation: Center for Advanced Imaging and Innovation and Research (CAI2R) and.|Department of Radiology, Bernard and Irene Schwartz Center for Biomedical Imaging, New York University School of Medicine New York, New York, USA.|Sackler Institute of Graduate Biomedical Sciences, New York University School of Medicine New York, New York, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Feng
authors.affiliation: Pattern Recognition Lab, FAU Erlangen-Nuremberg, Erlangen, Germany.|Siemens AG Healthcare MR, Erlangen, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Grimm
authors.affiliation: Center for Advanced Imaging and Innovation and Research (CAI2R) and.|Department of Radiology, Bernard and Irene Schwartz Center for Biomedical Imaging, New York University School of Medicine New York, New York, USA.
authors.forename: Melanie
authors.initials: M
authors.lastname: Freed
authors.affiliation: Center for Advanced Imaging and Innovation and Research (CAI2R) and.|Department of Radiology, Bernard and Irene Schwartz Center for Biomedical Imaging, New York University School of Medicine New York, New York, USA.
authors.forename: Kai Tobias
authors.initials: KT
authors.lastname: Block
authors.affiliation: Center for Advanced Imaging and Innovation and Research (CAI2R) and.|Department of Radiology, Bernard and Irene Schwartz Center for Biomedical Imaging, New York University School of Medicine New York, New York, USA.
authors.forename: Daniel K
authors.initials: DK
authors.lastname: Sodickson
authors.affiliation: Center for Advanced Imaging and Innovation and Research (CAI2R) and.|Department of Radiology, Bernard and Irene Schwartz Center for Biomedical Imaging, New York University School of Medicine New York, New York, USA.
authors.forename: Linda
authors.initials: L
authors.lastname: Moy
authors.affiliation: Center for Advanced Imaging and Innovation and Research (CAI2R) and.|Department of Radiology, Bernard and Irene Schwartz Center for Biomedical Imaging, New York University School of Medicine New York, New York, USA.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Otazo
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001943:Breast Neoplasms / Q000473:pathology*; D003287:Contrast Media; D044962:Data Compression / Q000379:methods*; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015203:Reproducibility of Results; D018401:Sample Size; D012680:Sensitivity and Specificity; D062211:Spatio-Temporal Analysis
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA
keywords: DCE-MRI; breast cancer; compressed sensing; golden-angle; iGRASP; parallel imaging; radial undersampling; temporal sparsity