1084 A double-inversion radial FSE and GRASE methods for the evaluation of cardiac masses
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KeywordsAnatomical Image Breath Hold Cardiac Mass Tissue Characterization Water Image
CMR can provide valuable information for the characterization of cardiac masses. Currently, however, the characterization of cardiac masses with CMR is based on the qualitative assessment of image contrast in T2-weighted, T1-weighted, or fat-suppressed images with or without the additional benefit of contrast media. Because the contrast in a CMR image is determined by MR-dependent tissue parameters, the quantitative measurement of these parameters should provide a more accurate approach for tissue characterization.
Recently we developed a radial double-inversion fast spin-echo (DIR-FSE) technique for the rapid evaluation of the T2 relaxation time (Altbach et al, Magn Reson Med 54:549, 2005; Echocardiography 24:316, 2007). High-resolution radial DIR-FSE data for T2 calculation are obtained in a breath hold making the technique attractive for routine clinical practice. The radial DIR gradient and spin-echo (GRASE) technique has also been proposed (Li et al, ISMRM 14:625, 2006). With the latter fat-water information is obtained in addition to T2.
To demonstrate the utility of the radial DIR-FSE and DIR-GRASE techniques for characterizing cardiac masses.
Radial DIR-FSE data are processed as follows. A high-resolution anatomical image is reconstructed from the full radial k-space data set. High-resolution images at various TEeff are generated from the same k-space data set by using data corresponding to a specific TE in the central part of k-space, up to the Nyquist radius (Fig. 1c). Radial data acquired at TE≠TEeff are incorporated in a progressive manner from the Nyquist point to the outer part of k-space. T2 maps were generated from the TEeff images.
The TEeff images from DIR-GRASE data are obtained (as shown in Fig. 1c) using only the echoes closer to the SE period (E0). In order to obtain lipid-water information each of the four echoes in the GRASE sequence (E1–4) are used to reconstruct four images with different phase shifts between fat and water. An iterative algorithm is used to obtain a lipid and a water image without the effects of field inhomogeneities (Reeder et al, Magn Reson Med 51:35, 2004).
We showed that radial FSE or GRASE methods can be used for the quantitative evaluation of cardiac masses. Data for T2 and lipid-water information are obtained in a breath hold thus providing a faster and efficient approach for characterizing these pathologies. In this study we only used T2 and lipid-water information for mass characterization. Radial GRASE data can be processed to estimate T2*, in addition to T2 and lipid-water information, thus providing an additional parameter for tissue characterization.
Work supported by NIH grants (CA099074, HL085385) and the AHA.
This article is published under license to BioMed Central Ltd.