title: In vivo multiecho T2 relaxation measurements using variable TR to decrease scan time.
abstract: Multiecho T2 relaxation measurements to determine geometric mean T2 (GMT2) and myelin water fraction (MWF) are lengthy, resulting in increased motion artefacts from patient discomfort and reduced patient compliance. The goal of this study was to shorten the acquisition time for multiecho T2 measurements without affecting T1 weighting by varying TR across k-space. Six phantoms and 10 healthy volunteers were imaged with both a constant TR and a variable TR multiecho T2 sequence. T1 weighting was determined by TR at the center of k-space; for variable TR measurement, TR was shortened linearly from the center to the edges of k-space. Phantoms showed excellent agreement for proton density and GMT2 between constant and variable TR measurements. No significant differences were found in proton density or MWF for any of the brain structures between the two measurements. The average GMT2 over all structures between the two experiments was not significantly different. In summary, with the variable TR approach, scan time was reduced by >20%, with minimal loss of image resolution and no significant affect on proton density, MWF or GMT2.
authors.affiliation: Department of Radiology, University of British Columbia Hospital, Vancouver BC, Canada V6T 2B5. claule@physics.ubc.ca
authors.forename: Cornelia
authors.initials: C
authors.lastname: Laule
authors.forename: Shannon Heather
authors.initials: SH
authors.lastname: Kolind
authors.forename: Thorarin Albert
authors.initials: TA
authors.lastname: Bjarnason
authors.forename: David Kwok Boon
authors.initials: DK
authors.lastname: Li
authors.forename: Alex Lloyd
authors.initials: AL
authors.lastname: MacKay
mesh_terms: D000328:Adult; D000465:Algorithms; D001921:Brain / Q000473:pathology*; D005260:Female; D006801:Humans; D007089:Image Enhancement; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015233:Models, Statistical; D008962:Models, Theoretical; D009186:Myelin Sheath / Q000737:chemistry; D019047:Phantoms, Imaging; D011522:Protons; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D011522:Protons; D014867:Water