Myocardial T2 mapping with respiratory navigator and automatic nonrigid motion correction

Quantitative T2 mapping was recently shown to be superior to T2-weighted imaging in detecting T2 changes across myocardium. Pixel-wise T2 mapping is sensitive to misregistration between the images used to generate the parameter map. In this study, utility of two motion-compensation strategies(i) navigator gating with prospective slice correction and (ii) nonrigid registrationwas investigated for myocardial T2 mapping in short axis and horizontal long axis views. Navigator gating provides respiratory motion compensation, whereas registration corrects for residual cardiac and respiratory motion between images; thus, the two strategies provided complementary functions. When these were combined, respiratory-motion-induced T2 variability, as measured by both standard deviation and interquartile range, was comparable to that in breath-hold T2 maps. In normal subjects, this combined motion-compensation strategy increased the percentage of myocardium with T2 measured to be within normal range from 60.1% to 92.2% in short axis and 62.3% to 92.7% in horizontal long axis. The new motion-compensated T2 mapping technique, which combines navigator gating, prospective slice correction, and nonrigid registration to provide through-plane and in-plane motion correction, enables a method for fully automatic and robust free-breathing T2 mapping. Magn Reson Med, 2012. (c) 2012 Wiley Periodicals, Inc.