title: Free-breathing 3 T magnetic resonance T2-mapping of the heart.
abstract: OBJECTIVE
  This study sought to establish an accurate and reproducible T(2)-mapping cardiac magnetic resonance (CMR) methodology at 3 T and to evaluate it in healthy volunteers and patients with myocardial infarct.
  
  
  BACKGROUND
  Myocardial edema affects the T(2) relaxation time on CMR. Therefore, T(2)-mapping has been established to characterize edema at 1.5 T. A 3 T implementation designed for longitudinal studies and aimed at guiding and monitoring therapy remains to be implemented, thoroughly characterized, and evaluated in vivo.
  
  
  METHODS
  A free-breathing navigator-gated radial CMR pulse sequence with an adiabatic T(2) preparation module and an empirical fitting equation for T(2) quantification was optimized using numerical simulations and was validated at 3 T in a phantom study. Its reproducibility for myocardial T(2) quantification was then ascertained in healthy volunteers and improved using an external reference phantom with known T(2). In a small cohort of patients with established myocardial infarction, the local T(2) value and extent of the edematous region were determined and compared with conventional T(2)-weighted CMR and x-ray coronary angiography, where available.
  
  
  RESULTS
  The numerical simulations and phantom study demonstrated that the empirical fitting equation is significantly more accurate for T(2) quantification than that for the more conventional exponential decay. The volunteer study consistently demonstrated a reproducibility error as low as 2 ± 1% using the external reference phantom and an average myocardial T(2) of 38.5 ± 4.5 ms. Intraobserver and interobserver variability in the volunteers were -0.04 ± 0.89 ms (p = 0.86) and -0.23 ± 0.91 ms (p = 0.87), respectively. In the infarction patients, the T(2) in edema was 62.4 ± 9.2 ms and was consistent with the x-ray angiographic findings. Simultaneously, the extent of the edematous region by T(2)-mapping correlated well with that from the T(2)-weighted images (r = 0.91).
  
  
  CONCLUSIONS
  The new, well-characterized 3 T methodology enables robust and accurate cardiac T(2)-mapping at 3 T with high spatial resolution, while the addition of a reference phantom improves reproducibility. This technique may be well suited for longitudinal studies in patients with suspected or established heart disease.
authors.affiliation: Department of Radiology, University Hospital of Lausanne (CHUV), Lausanne, Switzerland. ruud.mri@gmail.com
authors.forename: Ruud B
authors.initials: RB
authors.lastname: van Heeswijk
authors.forename: Hélène
authors.initials: H
authors.lastname: Feliciano
authors.forename: Cédric
authors.initials: C
authors.lastname: Bongard
authors.forename: Gabriele
authors.initials: G
authors.lastname: Bonanno
authors.forename: Simone
authors.initials: S
authors.lastname: Coppo
authors.forename: Nathalie
authors.initials: N
authors.lastname: Lauriers
authors.forename: Didier
authors.initials: D
authors.lastname: Locca
authors.forename: Juerg
authors.initials: J
authors.lastname: Schwitter
authors.forename: Matthias
authors.initials: M
authors.lastname: Stuber
mesh_terms: D000328:Adult; D003326:Coronary Circulation / Q000502:physiology*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D009203:Myocardial Infarction / Q000175:diagnosis* / Q000503:physiopathology; D009206:Myocardium / Q000473:pathology*; D019047:Phantoms, Imaging; D012372:ROC Curve; D015203:Reproducibility of Results