title: Identifying systematic errors in quantitative dynamic-susceptibility contrast perfusion imaging by high-resolution multi-echo parallel EPI.
abstract: Several obstacles usually confound a straightforward perfusion analysis using dynamic-susceptibility contrast-based magnetic resonance imaging (DSC-MRI). In this work, it became possible to eliminate some of these sources of error by combining a multiple gradient-echo technique with parallel imaging (PI): first, the large dynamic range of tracer concentrations could be covered satisfactorily with multiple echo times (TE) which would otherwise result in overestimation of image magnitude in the presence of noise. Second, any bias from T(1) relaxation could be avoided by fitting to the signal magnitude of multiple TEs. Finally, with PI, a good tradeoff can be achieved between number of echoes, brain coverage, temporal resolution and spatial resolution. The latter reduces partial voluming, which could distort calculation of the arterial input function. Having ruled out these sources of error, a 4-fold overestimation of cerebral blood volume and flow remained, which was most likely due to the completely different relaxation mechanisms that are effective in arterial voxels compared with tissue. Hence, the uniform tissue-independent linear dependency of relaxation rate upon tracer concentration, which is usually assumed, must be questioned. Therefore, DSC-MRI requires knowledge of the exact dependency of transverse relaxation rate upon tracer concentration in order to calculate truly quantitative perfusion maps.
authors.affiliation: Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstr. 1a, D-04103 Leipzig, Germany. thies@jochimsen-sh.de
authors.forename: Thies H
authors.initials: TH
authors.lastname: Jochimsen
authors.forename: Rexford D
authors.initials: RD
authors.lastname: Newbould
authors.forename: Stefan T
authors.initials: ST
authors.lastname: Skare
authors.forename: David B
authors.initials: DB
authors.lastname: Clayton
authors.forename: Gregory W
authors.initials: GW
authors.lastname: Albers
authors.forename: Michael E
authors.initials: ME
authors.lastname: Moseley
authors.forename: Roland
authors.initials: R
authors.lastname: Bammer
mesh_terms: D001921:Brain / Q000098:blood supply / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003287:Contrast Media; D017352:Echo-Planar Imaging / Q000379:methods*; D019786:Gadolinium DTPA; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D010477:Perfusion / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA