Editorial for "The Role of Improved Motion-Sensitized Driven Equilibrium Blood Suppression and Fat Saturation on T2 Relaxation Time, Using GraSE Sequence in Cardiac Magnetic Resonance Imaging".

T2 mapping has been established as one of the key sequences measured during cardiac magnetic resonance imaging (MRI) examinations. It provides important information about myocardial characteristics and may indicate the presence of structural abnormalities. Specifically, T2-weighted imaging (T2w) and T2 mapping provide information about myocardial water content in the presence of, eg, myocardial edema.1 Whereas T2w imaging relies on semiquantitative comparison of signal intensities, T2 mapping provides a quantitative measure. It offers various advantages over T2w imaging including lower sensitivity to motion, less variation in signal intensity, better detection of endocardial borders, and higher objectivity.2 In clinical settings, this can be used as a diagnostic tool for various diseases, eg, inflammation in myocarditis as well as various forms of cardiomyopathies.3, 4 T2 mapping even has proven of prognostic value in patients after acute myocardial infarction and in myocarditis.5, 6 While T2 mapping holds promise as a robust sequence in evaluating the structural alterations of the myocard, several challenges such as sensitivity to T1, susceptibility to arrhythmia, and off-resonance effects need to be considered.4 These challenges have been addressed by implementing faster acquisition, improving bias through fitting model optimization, or increasing spatial coverage.2, 7 Tachyarrhythmia still influences image quality of T2 mapping, especially with respect to artifacts and insufficient suppression of the flowing blood. A wide range of T2 mapping strategies each with its own advantages and disadvantages, such as multi-echo spin echo (MESE), T2-prepared balanced steady-state free precession (T2-prep bSSFP), and gradient-spin echo (GraSE), exist.4 GraSE T2 mapping as a combination of a turbo spin echo (TSE) with echo-planar imaging (EPI) provides advantages over T2-prep bSSFB, such as reduced susceptibility to magnetic field inhomogeneities. This facilitates the acquisition of images with additional blood suppression techniques.8 Application of blood suppression enhances the accuracy of T2 mapping, but may cause susceptibility to arrhythmia again. For example, the widely used double inversion recovery (DIR) pre-pulse requires a time delay of several hundred milliseconds and alternative acquisition schemes lead to increased scan time. The complex flow patterns within the cardiac chambers may further influence blood suppression techniques.9 This raises the medical need to develop blood suppression techniques that are less prone to arrhythmia. Therefore, understanding the advantages and limitations of different blood suppression techniques in T2 mapping is essential for optimizing cardiac MRI protocols in various clinical settings to improve diagnostic accuracy. In this issue of JMRI, the article by Dehghani et al10 advances previous cardiac MRI studies by validating an improved motion-sensitized driven equilibrium (iMSDE) T2 GraSE sequence against DIR for blood suppression especially designed for patients with tachyarrhythmia. In healthy subjects, the study showed that global T2 values were not significantly different between the iMSDE and DIR sequences independent of applying an additional fat suppression technique. Measurements were consistent between basal, midventricular, and apical slices. Various age groups and different gender did not influence measurements between the different sequences. Intra- and interobserver variability was very good in iMSDE and DIR, both with and without fat suppression. In addition, image quality scores showed comparable values in addition to a similar appearance of respiratory motion and susceptibility artifacts. Finally, acquisition time, signal-to-noise, and contrast-to-noise of the myocardium and blood pool ratios were not significantly different. As the study was conducted on healthy subjects, the value of the iMSDE T2 GraSE sequence in patients with (tachy-)arrhythmia or those with irregular breathing patterns remains to be determined, especially with regard to artifacts and acquisition time. However, the publication by Dehghani et al is yet another important step in optimizing T2 mapping sequences for the application in various and complicated circumstances in the clinical setting.