title: Signal-to-noise ratio increase in carotid atheroma MRI: a comparison of 1.5 and 3 T.
abstract: OBJECTIVE
  This study reports quantitative comparisons of signal-to-noise ratio (SNR) at 1.5 and 3 T from images of carotid atheroma obtained using a multicontrast, cardiac-gated, blood-suppressed fast spin echo protocol.
  
  
  METHODS
  18 subjects, with carotid atherosclerosis (>30% stenosis) confirmed on ultrasound, were imaged on both 1.5 and 3 T systems using phased-array coils with matched hardware specifications. T(1) weighted (T(1)W), T(2) weighted (T(2)W) and proton density-weighted (PDW) images were acquired with identical scan times. Multiple slices were prescribed to encompass both the carotid bifurcation and the plaque. Image quality was quantified using the SNR and contrast-to-noise ratio (CNR). A phantom experiment was also performed to validate the SNR method and confirm the size of the improvement in SNR. Comparisons of the SNR values from the vessel wall with muscle and plaque/lumen CNR measurements were performed at a patient level. To account for the multiple comparisons a Bonferroni correction was applied.
  
  
  RESULTS
  One subject was excluded from the protocol owing to image quality and protocol failure. The mean improvement in SNR in plaque was 1.9, 2.1 and 2.1 in T(1)W, T(2)W and PDW images, respectively. All plaque SNR improvements were statistically significant at the p<0.05 level. The phantom experiment reported an improvement in SNR of 2.4 for PDW images.
  
  
  CONCLUSIONS
  Significant gains in SNR can be obtained for carotid atheroma imaging at 3 T compared with 1.5 T. There was also a trend towards increased CNR. However, this was not significant after the application of the Bonferroni correction.
authors.affiliation: Department of Radiology, Addenbrookes Hospital, Cambridge, UK. vy207@cam.ac.uk
authors.forename: V E
authors.initials: VE
authors.lastname: Young
authors.forename: A J
authors.initials: AJ
authors.lastname: Patterson
authors.forename: E M
authors.initials: EM
authors.lastname: Tunnicliffe
authors.forename: U
authors.initials: U
authors.lastname: Sadat
authors.forename: M J
authors.initials: MJ
authors.lastname: Graves
authors.forename: T Y
authors.initials: TY
authors.lastname: Tang
authors.forename: A N
authors.initials: AN
authors.lastname: Priest
authors.forename: P J
authors.initials: PJ
authors.lastname: Kirkpatrick
authors.forename: J H
authors.initials: JH
authors.lastname: Gillard
mesh_terms: D000368:Aged; D016893:Carotid Stenosis / Q000175:diagnosis* / Q000000981:diagnostic imaging; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D056888:Patient Positioning; D019047:Phantoms, Imaging; D058226:Plaque, Atherosclerotic / Q000175:diagnosis* / Q000000981:diagnostic imaging; D011446:Prospective Studies; D011786:Quality Control; D011856:Radiographic Image Enhancement; D012720:Severity of Illness Index; D059629:Signal-To-Noise Ratio; D018709:Statistics, Nonparametric; D018608:Ultrasonography, Doppler