Abstract
PurposeTo develop a free-breathing whole-heart isotropic-resolution 3D late gadolinium enhancement (LGE) sequence with Dixon-encoding, which provides co-registered 3D grey-blood phase-sensitive inversion-recovery (PSIR) and complementary 3D fat volumes in a single scan of < 7 min.MethodsA free-breathing 3D PSIR LGE sequence with dual-echo Dixon readout with a variable density Cartesian trajectory with acceleration factor of 3 is proposed. Image navigators are acquired to correct both inversion recovery (IR)-prepared and reference volumes for 2D translational respiratory motion, enabling motion compensated PSIR reconstruction with 100% respiratory scan efficiency. An intermediate PSIR reconstruction is performed between the in-phase echoes to estimate the signal polarity which is subsequently applied to the IR-prepared water volume to generate a water grey-blood PSIR image. The IR-prepared water volume is obtained using a water/fat separation algorithm from the corresponding dual-echo readout. The complementary fat-volume is obtained after water/fat separation of the reference volume. Ten patients (6 with myocardial scar) were scanned with the proposed water/fat grey-blood 3D PSIR LGE sequence at 1.5 T and compared to breath-held grey-blood 2D LGE sequence in terms of contrast ratio (CR), contrast-to-noise ratio (CNR), scar depiction, scar transmurality, scar mass and image quality.ResultsComparable CRs (p = 0.98, 0.40 and 0.83) and CNRs (p = 0.29, 0.40 and 0.26) for blood-myocardium, scar-myocardium and scar-blood respectively were obtained with the proposed free-breathing 3D water/fat LGE and 2D clinical LGE scan. Excellent agreement for scar detection, scar transmurality, scar mass (bias = 0.29%) and image quality scores (from 1: non-diagnostic to 4: excellent) of 3.8 ± 0.42 and 3.6 ± 0.69 (p > 0.99) were obtained with the 2D and 3D PSIR LGE approaches with comparable total acquisition time (p = 0.29). Similar agreement in intra and inter-observer variability were obtained for the 2D and 3D acquisition respectively.ConclusionThe proposed approach enabled the acquisition of free-breathing motion-compensated isotropic-resolution 3D grey-blood PSIR LGE and fat volumes. The proposed approach showed good agreement with conventional 2D LGE in terms of CR, scar depiction and scan time, while enabling free-breathing acquisition, whole-heart coverage, reformatting in arbitrary views and visualization of both water and fat information.
Highlights
Late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) plays an important role in the assessment of ischemic heart diseases and myocardial viability [1, 2]
An intermediate phase-sensitive inversion-recovery (PSIR) [9] reconstruction is performed between the two in-phase datasets prior to water/fat separation to estimate the signal polarity which is subsequently reapplied to the inversion recovery (IR)-prepared magnitude water volume to generate a water grey-blood PSIR image
contrast ratio (CR) and contrast-to-noise ratio (CNR) analysis were carried out on the PSIR images reconstructed for magnitude blood-nulling (TI = 240 ms) and magnitude myocardium-nulling (TI = 395 ms) (Fig. 2c, d)
Summary
Late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) plays an important role in the assessment of ischemic heart diseases and myocardial viability [1, 2]. The acquisition scheme usually consists of an inversion recovery (IR) pulse followed by a waiting time, called inversion time (TI), and signal readout. With this approach the TI is usually chosen to null the signal from healthy myocardium, enhancing the infarcted myocardium due to the retention of GBCA [5, 6]. This so-called “bright-blood” method achieves high contrast between ischemic and healthy myocardium, the bright signal from the adjacent blood pool hinders scar delineation at the blood-scar border [7]. Heart rate variations during the acquisition can impair the choice of the TI, resulting in suboptimal scar visualization [8]
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