Myocardial T*2 measurement in iron-overloaded thalassemia: an ex vivo study to investigate optimal methods of quantification.

Myocardial T*2 measurement has been increasingly used for iron quantification to assess the risk of cardiac complications in thalassemia patients. In this study the noise effects were evaluated along with different curve-fitting models on an iron overloaded ex vivo heart in order to determine the optimal method of T*2 measurement and to help understand issues affecting reproducibility and accuracy. Gradient multiecho short axis images were acquired with differing numbers of excitations to generate varying signal-to-noise ratio (SNR) images. A noise correction method was implemented; linear and nonlinear curve-fitting algorithms were compared and different curve-fitting models (monoexponential, truncation, baseline subtraction, and offset) were evaluated. This study suggests that the T*2 decay curve in an ex vivo heart can be fitted by a monoexponential model and accurate T*2 measurements can be obtained with proper noise correction. With MRI noise, T*2 is generally overestimated by including late low SNR data points, but underestimated by the offset or baseline subtraction models, which are in fact equivalent. In this situation the truncation model proves to be reproducible and more accurate than the other models. The study also shows that the nonlinear algorithm is preferred in T*2 curve fitting. (c) 2008 Wiley-Liss, Inc.