A dual flip angle 3D bSSFP magnetization transfer-like method to differentiate between recent and old myocardial infarction.

Germain, Philippe; El Ghannudi, Soraya; Labani, Aissam; Jeung, Mi Y.; Gangi, Afshin; Ohlmann, Patrick; Roy, Catherine

<bold>Background: </bold>Magnetic resonance imaging (MRI) tissue signal is modulated by magnetization transfer (MT) phenomena, intrinsically induced by balanced steady-state free precession (bSSFP) imaging.<bold>Purpose: </bold>To investigate the possible value of such a MT-like bSSFP approach in two clinical settings involving focal myocardial lesions highligthed by late gadolinium enhancement (LGE+): edema induced by recent myocardial infarction (MI) and fibrotic scar related to chronic infarction.<bold>Materials and Methods: </bold>Population: 48 LGE + patients were studied: 26 with recent MI, 22 with chronic MI. 20 LGE-normal subjects were considered the control group. Field strength/sequence: Navigator-based short axis 3D-bSSFP sequences with 20° and 90° excitation flip angles were acquired (1.5T).<bold>Assessment: </bold>Pixel-wise normalized MT Ratio (nMTR) parametric images were calculated according to: nMTR = 100*(S20 -S90 *k)/S20 , with S20 and S90 signal intensity in 20° and 90° flip angle images and k = Blood20 /Blood90 as a normalization ratio. Statistical tests: analysis of variance (ANOVA), receiver operating characteristic (ROC) analysis.<bold>Results: </bold>Overall normal myocardial nMTR was 50.2 ± 3.6%. In recent MI, nMTR values were significantly reduced in LGE + regions (-22.3 ± 9.9%, P < 0.0001). In cases of chronic infarct, nMTR was significantly increased in LGE + regions (14.2 ± 11.4%, P < 0.0001). Comparison between observed results and theoretical values obtained with the Freeman-Hill formula showed that most variations observed in MI are related to MT effects instead of relaxation effects.<bold>Conclusion: </bold>In contrast to LGE imaging, which may show a similar hyperenhancement in recent and old infarctions, nMTR imaging demonstrates an opposite pattern: decreased values for recent infarction and increased values for old infarction, thus allowing to discriminate between these two clinical conditions without gadolinium injection.<bold>Level Of Evidence: </bold>3 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:798-808.

Journal of Magnetic Resonance Imaging, 2018, Vol 47, Issue 3, p798

1053-1807

Academic Journal

10.1002/jmri.25821