title: Ultrahigh-field 7-T magnetic resonance carotid vessel wall imaging: initial experience in comparison with 3-T field strength.
abstract: OBJECTIVE
  Magnetic resonance imaging (MRI) of the vessel wall enables determination of luminal area, vessel wall thickness, and atherosclerotic plaque characteristics. For clinical application, high spatial resolution, derived from optimal signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), is paramount. Vessel wall MRI is expected to benefit from higher magnetic field strength. Therefore, the purposes of the present study were to develop an ultrahigh-field 7-T MRI hardware and protocols for vessel wall imaging of the carotid artery and to compare quantitative parameters of vessel wall morphology and image quality between 3-T and 7-T MRI.
  
  
  METHODS
  Eighteen volunteers (11 men and 7 women; mean [SD] age, 29 [7] years) underwent MRI examinations at 7 T (using a custom-built surface transmit/receive coil of 15-cm diameter) and at 3 T (using a commercial phased-array coil with 2 flexible oval elements, 14 × 17 cm each). Magnetic resonance imaging of the left common carotid artery vessel wall was performed at 7 T with identical in-plane resolution as that of 3-T MRI (0.46 × 0.46 mm), providing transverse T1- and T2-weighted images. Blinded analysis of morphologic measurements (luminal area and vessel wall area), SNR for vessel wall (SNRVW), and the CNR between the lumen and the vessel wall were compared between 7 and 3 T.
  
  
  RESULTS
  Morphologic carotid vessel wall measurements were comparable between 7 and 3 T for both T1-weighted images (luminal area: intraclass correlation [ICC], 0.81 and vessel wall area: ICC, 0.84) and T2-weighted images (luminal area: ICC, 0.97 and vessel wall area: ICC, 0.92). At 7 T, SNRVW and CNR were significantly higher compared with 3-T MRI for both T1- (P < 0.001) and T2-weighted images (P < 0.05), with gain factors ranging from 1.3 to 3.6.
  
  
  CONCLUSIONS
  Ultrahigh-field 7-T MR carotid vessel wall imaging is feasible. 7-T MRI of the common carotid artery has comparable accuracy for determining luminal area and vessel wall area and has improved SNRVW and CNR compared with 3-T MRI. Therefore, ultrahigh-field 7-T vessel wall MRI may enable a more detailed assessment of plaque morphology.
authors.affiliation: Department of Cardiology, Leiden University Medical Center, Leiden, the Netherlands. e.s.j.kroner@lumc.nl
authors.forename: Eleanore S J
authors.initials: ES
authors.lastname: Kröner
authors.forename: Linda D
authors.initials: LD
authors.lastname: van Schinkel
authors.forename: Maarten J
authors.initials: MJ
authors.lastname: Versluis
authors.forename: Niels J
authors.initials: NJ
authors.lastname: Brouwer
authors.forename: Pieter J
authors.initials: PJ
authors.lastname: van den Boogaard
authors.forename: Ernst E
authors.initials: EE
authors.lastname: van der Wall
authors.forename: Albert
authors.initials: A
authors.lastname: de Roos
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Webb
authors.forename: Hans-Marc J
authors.initials: HM
authors.lastname: Siebelink
authors.forename: Hildo J
authors.initials: HJ
authors.lastname: Lamb
mesh_terms: D000328:Adult; D002339:Carotid Arteries / Q000033:anatomy & histology*; D002985:Clinical Protocols; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male