title: Cerebral microbleeds: burden assessment by using quantitative susceptibility mapping.
abstract: OBJECTIVE
  To assess quantitative susceptibility mapping (QSM) for reducing the inconsistency of standard magnetic resonance (MR) imaging sequences in measurements of cerebral microbleed burden.
  
  
  METHODS
  This retrospective study was HIPAA compliant and institutional review board approved. Ten patients (5.6%) were selected from among 178 consecutive patients suspected of having experienced a stroke who were imaged with a multiecho gradient-echo sequence at 3.0 T and who had cerebral microbleeds on T2*-weighted images. QSM was performed for various ranges of echo time by using both the magnitude and phase components in the morphology-enabled dipole inversion method. Cerebral microbleed size was measured by two neuroradiologists on QSM images, T2*-weighted images, susceptibility-weighted (SW) images, and R2* maps calculated by using different echo times. The sum of susceptibility over a region containing a cerebral microbleed was also estimated on QSM images as its total susceptibility. Measurement differences were assessed by using the Student t test and the F test; P < .05 was considered to indicate a statistically significant difference.
  
  
  RESULTS
  When echo time was increased from approximately 20 to 40 msec, the measured cerebral microbleed volume increased by mean factors of 1.49 ± 0.86 (standard deviation), 1.64 ± 0.84, 2.30 ± 1.20, and 2.30 ± 1.19 for QSM, R2*, T2*-weighted, and SW images, respectively (P < .01). However, the measured total susceptibility with QSM did not show significant change over echo time (P = .31), and the variation was significantly smaller than any of the volume increases (P < .01 for each).
  
  
  CONCLUSIONS
  The total susceptibility of a cerebral microbleed measured by using QSM is a physical property that is independent of echo time.
authors: Department of Biomedical Engineering, Cornell University, Ithaca, NY, USA.
authors: Tian
authors: T
authors: Liu
authors: Krishna
authors: K
authors: Surapaneni
authors: Min
authors: M
authors: Lou
authors: Liuquan
authors: L
authors: Cheng
authors: Pascal
authors: P
authors: Spincemaille
authors: Yi
authors: Y
authors: Wang
mesh_terms: D000368:Aged; D000465:Algorithms; D000704:Analysis of Variance; D002543:Cerebral Hemorrhage / Q000175:diagnosis*; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D012189:Retrospective Studies