title: Investigating the influence of flip angle and k-space sampling on dynamic contrast-enhanced MRI breast examinations.
abstract: OBJECTIVE
  To retrospectively investigate the effect of flip angle (FA) and k-space sampling on the performance of dynamic contrast-enhanced (DCE-) magnetic resonance imaging (MRI) breast sequences.
  
  
  METHODS
  Five DCE-MRI breast sequences were evaluated (10°, 14°, and 18° FAs; radial or linear k-space sampling), with 7-10 patients in each group (n = 45). All sequences were compliant with current technical breast screening guidelines. Contrast agent (CA) uptake curves were constructed from the right mammary artery for each examination. Maximum relative enhancement, E(max), and time-to-peak enhancement, T(max), were measured and compared between protocols (analysis of variance and Mann-Whitney). For each sequence, calculated values of maximum relative enhancement, E(calc), were derived from the Bloch equations and compared to E(max). Fat suppression performance (residual bright fat and chemical shift artifact) was rated for each examination and compared between sequences (Fisher exact tests).
  
  
  RESULTS
  Significant differences were identified between DCE-MRI sequences. E(max) increased significantly at higher FAs and with linear k-space sampling (P < .0001; P = .001). Radial protocols exhibited greater T(max) than linear protocols at FAs of both 14° (P = .025) and 18° (P < .0001), suggesting artificially flattened uptake curves. Good correlation was observed between E(calc) and E(max) (r = 0.86). Fat suppression failure was more pronounced at an FA of 18° (P = .008).
  
  
  CONCLUSIONS
  This retrospective approach is validated as a tool to compare and optimize breast DCE-MRI sequences. Alterations in FA and k-space sampling result in significant differences in CA uptake curve shape which could potentially affect diagnostic interpretation. These results emphasize the need for careful parameter selection and greater standardization of breast DCE-MRI sequences.
authors.affiliation: Cancer Research - United Kingdom (CR-UK) Cancer Imaging Centre, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Downs Rd, Sutton, Surrey SM2 5PT, United Kingdom.
authors.forename: Araminta E W
authors.initials: AE
authors.lastname: Ledger
authors.affiliation: Cancer Research - United Kingdom (CR-UK) Cancer Imaging Centre, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Downs Rd, Sutton, Surrey SM2 5PT, United Kingdom.
authors.forename: Marco
authors.initials: M
authors.lastname: Borri
authors.affiliation: Department of Radiology, Royal Marsden Hospital, Sutton, Surrey, United Kingdom.
authors.forename: Romney J E
authors.initials: RJ
authors.lastname: Pope
authors.affiliation: Department of Radiology, Royal Marsden Hospital, Sutton, Surrey, United Kingdom.
authors.forename: Erica D
authors.initials: ED
authors.lastname: Scurr
authors.affiliation: Department of Radiology, Royal Marsden Hospital, Sutton, Surrey, United Kingdom.
authors.forename: Toni
authors.initials: T
authors.lastname: Wallace
authors.affiliation: Department of Radiology, Royal Marsden Hospital, Sutton, Surrey, United Kingdom.
authors.forename: Cheryl
authors.initials: C
authors.lastname: Richardson
authors.affiliation: Department of Radiology, Royal Marsden Hospital, Sutton, Surrey, United Kingdom.
authors.forename: Marianne
authors.initials: M
authors.lastname: Usher
authors.affiliation: Department of Radiology, Royal Marsden Hospital, Sutton, Surrey, United Kingdom.
authors.forename: Steven
authors.initials: S
authors.lastname: Allen
authors.affiliation: Department of Radiology, Royal Marsden Hospital, Sutton, Surrey, United Kingdom.
authors.forename: Robin M
authors.initials: RM
authors.lastname: Wilson
authors.affiliation: Clinical Research and Development, Royal Marsden Hospital, Sutton, Surrey, United Kingdom.
authors.forename: Karen
authors.initials: K
authors.lastname: Thomas
authors.affiliation: Cancer Research - United Kingdom (CR-UK) Cancer Imaging Centre, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Downs Rd, Sutton, Surrey SM2 5PT, United Kingdom.
authors.forename: Nandita M
authors.initials: NM
authors.lastname: deSouza
authors.affiliation: Cancer Research - United Kingdom (CR-UK) Cancer Imaging Centre, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Downs Rd, Sutton, Surrey SM2 5PT, United Kingdom. Electronic address: Martin.Leach@icr.ac.uk.
authors.forename: Martin O
authors.initials: MO
authors.lastname: Leach
authors.affiliation: Cancer Research - United Kingdom (CR-UK) Cancer Imaging Centre, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Downs Rd, Sutton, Surrey SM2 5PT, United Kingdom.
authors.forename: Maria A
authors.initials: MA
authors.lastname: Schmidt
mesh_terms: D000465:Algorithms; D001943:Breast Neoplasms / Q000473:pathology*; D003287:Contrast Media; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008536:Meglumine; D009942:Organometallic Compounds; D015203:Reproducibility of Results; D018401:Sample Size; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted
chemical_list: D003287:Contrast Media; D009942:Organometallic Compounds; D008536:Meglumine; C072417:gadoterate meglumine
keywords: Breast imaging; MRI; contrast agents; enhancement; quality assurance