title: Impact of motion correction on reproducibility and spatial variability of quantitative myocardial T2 mapping.
abstract: BACKGROUND
  To evaluate and quantify the impact of a novel image-based motion correction technique in myocardial T2 mapping in terms of measurement reproducibility and spatial variability.
  
  
  METHODS
  Twelve healthy adult subjects were imaged using breath-hold (BH), free breathing (FB), and free breathing with respiratory navigator gating (FB + NAV) myocardial T2 mapping sequences. Fifty patients referred for clinical CMR were imaged using the FB + NAV sequence. All sequences used a T2 prepared (T2prep) steady-state free precession acquisition. In-plane myocardial motion was corrected using an adaptive registration of varying contrast-weighted images for improved tissue characterization (ARCTIC). DICE similarity coefficient (DSC) and myocardial boundary errors (MBE) were measured to quantify the motion estimation accuracy in healthy subjects. T2 mapping reproducibility and spatial variability were evaluated in healthy subjects using 5 repetitions of the FB + NAV sequence with either 4 or 20 T2prep echo times (TE). Subjective T2 map quality was assessed in patients by an experienced reader using a 4-point scale (1-non diagnostic, 4-excellent).
  
  
  RESULTS
  ARCTIC led to increased DSC in BH data (0.85 ± 0.08 vs. 0.90 ± 0.02, p = 0.007), FB data (0.78 ± 0.13 vs. 0.90 ± 0.21, p < 0.001), and FB + NAV data (0.86 ± 0.05 vs. 0.90 ± 0.02, p = 0.002), and reduced MBE in BH data (0.90 ± 0.40 vs. 0.64 ± 0.19 mm, p = 0.005), FB data (1.21 ± 0.65 vs. 0.63 ± 0.10 mm, p < 0.001), and FB + NAV data (0.81 ± 0.21 vs. 0.63 ± 0.08 mm, p < 0.001). Improved reproducibility (4TE: 5.3 ± 2.5 ms vs. 4.0 ± 1.5 ms, p = 0.016; 20TE: 3.9 ± 2.3 ms vs. 2.2 ± 0.5 ms, p = 0.002), reduced spatial variability (4TE: 12.8 ± 3.5 ms vs. 10.3 ± 2.5 ms, p < 0.001; 20TE: 9.7 ± 3.5 ms vs. 7.5 ± 1.4 ms) and improved subjective score of T2 map quality (3.43 ± 0.79 vs. 3.69 ± 0.55, p < 0.001) were obtained using ARCTIC.
  
  
  CONCLUSIONS
  The ARCTIC technique substantially reduces spatial mis-alignment among T2-weighted images and improves the reproducibility and spatial variability of in-vivo T2 mapping.
authors.affiliation: Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA, 02215, USA. sroujol@bidmc.harvard.edu.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Roujol
authors.affiliation: Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA, 02215, USA. tbasha@bidmc.harvard.edu.|Biomedical Engineering Department, Cairo University, Giza, Egypt. tbasha@bidmc.harvard.edu.
authors.forename: Tamer A
authors.initials: TA
authors.lastname: Basha
authors.affiliation: Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA, 02215, USA. Basti@gmx.net.|Computer Assisted Clinical Medicine, University Medical Center Mannheim, Heidelberg University, Mannheim, Germany. Basti@gmx.net.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Weingärtner
authors.affiliation: Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA, 02215, USA. makcakay@bidmc.harvard.edu.
authors.forename: Mehmet
authors.initials: M
authors.lastname: Akçakaya
authors.affiliation: Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA, 02215, USA. sjberg@bidmc.harvard.edu.
authors.forename: Sophie
authors.initials: S
authors.lastname: Berg
authors.affiliation: Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA, 02215, USA. wmanning@bidmc.harvard.edu.|Radiology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA. wmanning@bidmc.harvard.edu.
authors.forename: Warren J
authors.initials: WJ
authors.lastname: Manning
authors.affiliation: Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA, 02215, USA. rnezafat@bidmc.harvard.edu.
authors.forename: Reza
authors.initials: R
authors.lastname: Nezafat
mesh_terms: D000293:Adolescent; D000328:Adult; D016477:Artifacts; D062485:Breath Holding; D005260:Female; D064368:Healthy Volunteers; D006321:Heart / Q000033:anatomy & histology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009068:Movement; D009206:Myocardium; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012119:Respiration; D055815:Young Adult