title: Robust T1-weighted structural brain imaging and morphometry at 7T using MP2RAGE.
abstract: OBJECTIVE
  To suppress the noise, by sacrificing some of the signal homogeneity for numerical stability, in uniform T1 weighted (T1w) images obtained with the magnetization prepared 2 rapid gradient echoes sequence (MP2RAGE) and to compare the clinical utility of these robust T1w images against the uniform T1w images.
  
  
  METHODS
  8 healthy subjects (29.0 ± 4.1 years; 6 Male), who provided written consent, underwent two scan sessions within a 24 hour period on a 7T head-only scanner. The uniform and robust T1w image volumes were calculated inline on the scanner. Two experienced radiologists qualitatively rated the images for: general image quality; 7T specific artefacts; and, local structure definition. Voxel-based and volume-based morphometry packages were used to compare the segmentation quality between the uniform and robust images. Statistical differences were evaluated by using a positive sided Wilcoxon rank test.
  
  
  RESULTS
  The robust image suppresses background noise inside and outside the skull. The inhomogeneity introduced was ranked as mild. The robust image was significantly ranked higher than the uniform image for both observers (observer 1/2, p-value = 0.0006/0.0004). In particular, an improved delineation of the pituitary gland, cerebellar lobes was observed in the robust versus uniform T1w image. The reproducibility of the segmentation results between repeat scans improved (p-value = 0.0004) from an average volumetric difference across structures of ≈ 6.6% to ≈ 2.4% for the uniform image and robust T1w image respectively.
  
  
  CONCLUSIONS
  The robust T1w image enables MP2RAGE to produce, clinically familiar T1w images, in addition to T1 maps, which can be readily used in uniform morphometry packages.
authors.affiliation: Centre d'Imagerie BioMédicale-Hôpitaux Universitaires de Genève, Department of Radiology, University of Geneva, Geneva, Switzerland; Advanced Clinical Imaging Technogoly, Centre d'Imagerie BioMédicale-Siemens, Lausanne, Switzerland.
authors.forename: Kieran R
authors.initials: KR
authors.lastname: O'Brien
authors.affiliation: Advanced Clinical Imaging Technogoly, Centre d'Imagerie BioMédicale-Siemens, Lausanne, Switzerland; Siemens Healthcare, Siemens Schweiz AG, Renens, Switzerland.
authors.forename: Tobias
authors.initials: T
authors.lastname: Kober
authors.affiliation: Department of Radiology, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
authors.forename: Patric
authors.initials: P
authors.lastname: Hagmann
authors.affiliation: Department of Radiology, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
authors.forename: Philippe
authors.initials: P
authors.lastname: Maeder
authors.affiliation: Centre d'Imagerie BioMédicale-Animal and Imaging Technology core, Department of Radiology, University of Lausanne, Lausanne, Switzerland.
authors.forename: José
authors.initials: J
authors.lastname: Marques
authors.affiliation: Centre d'Imagerie BioMédicale-Hôpitaux Universitaires de Genève, Department of Radiology, University of Geneva, Geneva, Switzerland.
authors.forename: Francois
authors.initials: F
authors.lastname: Lazeyras
authors.affiliation: Advanced Clinical Imaging Technogoly, Centre d'Imagerie BioMédicale-Siemens, Lausanne, Switzerland; Siemens Healthcare, Siemens Schweiz AG, Renens, Switzerland.
authors.forename: Gunnar
authors.initials: G
authors.lastname: Krueger
authors.affiliation: Advanced Clinical Imaging Technogoly, Centre d'Imagerie BioMédicale-Siemens, Lausanne, Switzerland; Siemens Healthcare, Siemens Schweiz AG, Renens, Switzerland; Department of Radiology, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
authors.forename: Alexis
authors.initials: A
authors.lastname: Roche
mesh_terms: D000328:Adult; D001921:Brain / Q000033:anatomy & histology*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D059906:Neuroimaging