title: Automated T(2) * measurements using supplementary field mapping to assess cardiac iron content.
abstract: OBJECTIVE
  To develop and evaluate an algorithm that automatically identifies high-susceptibility areas and excludes them from T(2) * measurements in the left ventricle (LV) for myocardial iron measurements.
  
  
  METHODS
  An autoregressive moving average (ARMA) model was implemented on multigradient echo scans of 24 patients (age range 3-45 years, 10 male/14 female). Voxels with relatively high susceptibility (>3 Hz/mm) were flagged and deselected from the T(2) * calculations for iron quantification. The mean, standard deviation, and coefficient of variation (CoV) of the ARMA-defined region were compared to the CoV of four distinct regions of the LV and the entire LV using a Student's t-test (α = 0.05).
  
  
  RESULTS
  The CoV of T(2) * values obtained by the ARMA method are comparable with that in the interventricular septum (IS), where susceptibility was the lowest (CoV = 0.31). The ARMA method provides a greater area (51.9 ± 13.7% of the LV) to measure T(2) * than that using the IS alone (21.1 ± 3.4%, P < 0.0001). Areas where low susceptibility are measured corroborate with areas reported in previous studies that investigated T(2) * variations throughout the LV.
  
  
  CONCLUSIONS
  An automated method to measure T(2) * relaxation in the LV with minimal effects from susceptibility has been developed. Variability is reduced while covering more regions for cardiac T2 * calculation.
authors.affiliation: Department of Radiological Sciences, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
authors.forename: Brian A
authors.initials: BA
authors.lastname: Taylor
authors.forename: Ralf B
authors.initials: RB
authors.lastname: Loeffler
authors.forename: Ruitian
authors.initials: R
authors.lastname: Song
authors.forename: Mary E
authors.initials: ME
authors.lastname: McCarville
authors.forename: Jane S
authors.initials: JS
authors.lastname: Hankins
authors.forename: Claudia M
authors.initials: CM
authors.lastname: Hillenbrand
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007501:Iron / Q000378:metabolism*; D019190:Iron Overload / Q000378:metabolism* / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D057054:Molecular Imaging / Q000379:methods; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D007501:Iron
keywords: T2* mapping; autoregressive moving average (ARMA) modeling; cardiac MR; iron overload; multigradient echo (mGRE); susceptibility