Head-to-head comparison of multiple cardiovascular magnetic resonance techniques for the detection and quantification of intramyocardial haemorrhage in patients with ST-elevation myocardial infarction.

OBJECTIVES: T2*-weighted (T2*w) is deemed as a reference standard for post-infarction intramyocardial haemorrhage (IMH). However, high proportion of T2* images is affected by off-resonance artefacts hampering image interpretation. Diagnostic accuracy and precision of alternative techniques for IMH diagnosis and quantification have been seldomly investigated. METHODS AND RESULTS: Between April 2016 and May 2017, 50 ST-segment elevation myocardial infarction patients (66% male, 57 ± 17 years) and 15 healthy controls (60% male, 58 ± 13) were consecutively enrolled. Subjects underwent head-to-head comparison of single mid-infarct slice acquired on black-blood T2-weighted short-TI-inversion recovery (T2w-STIR), bright-blood T2prep-steady-state-free precession (T2prep-SSFP), and T2/T1 maps for IMH diagnosis and quantification against T2*w. All images were graded for quality (grade 1: very poor; grade 4: excellent) and diagnostic confidence (Likert scale, 1: very unsure and 5: highly confident). Reduced relaxation time/hypointense region (hypocore) embedded in infarct-related oedema on T2 map, T1 map, and T2w-STIR had the best overall diagnostic accuracy (per-subject: 91%, 86%, and 86%, respectively; per segment: 95%, 93%, and 93%, respectively). By mixed-effects analysis, image quality, and diagnostic confidence were higher for T2 map and T1 maps than T2*w (p < 0.05 for both scores). For IMH quantification, hypocore on T2 map and T1 map strongly correlated (Spearman's r > 0.7, p < 0.001 for both) with IMH extent on T2*w and presented an overall excellent agreement on Bland-Altman analysis. By linear mixed model analysis, absolute hypocore size did not differ among T1-, T2 map, and T2*w. T2/T1 maps had the best intra- and inter-observer reproducibility among CMR techniques. CONCLUSION: Hypocore on T2/T1 map is the best alternative technique to T2*w for diagnosing and quantifying IMH in post-STEMI patients. KEY POINT: • Mapping techniques are the best alternatives for diagnosing post-infarction intramyocardial haemorrhage. • Mapping techniques are valuable tools for imaging intramyocardial haemorrhage.

Ultrashort echo time imaging of the lungs under high-frequency noninvasive ventilation: A new approach to lung imaging.

BACKGROUND: Although ultrashort echo time (UTE) sequences allow excellent assessment of lung parenchyma, image quality remains lower than that of computed tomography (CT). PURPOSE: To investigate a high-frequency noninvasive ventilation (HF-NIV) technique allowing a stabilized inspiration and to compare image quality with current dedicated MR sequences. STUDY TYPE: Prospective. POPULATION: Ten healthy volunteers. FIELD STRENGTH/SEQUENCE: 3D radial UTE sequence at 1.5T. ASSESSMENT: UTE-HF-NIV sequence was compared with UTE-free-breathing (UTE-FB), reconstructed at end expiration (UTE-Exp) and average (UTE-Avg), and breath-hold VIBE sequences. The distance from lung apex to the dome of the right hemidiaphragm was measured. Visual assessment of the visibility and sharpness of normal anatomical structures was carried out. Dedicated software also quantitatively evaluated vessel-lung and right lung-liver interface sharpness. Apparent signal ratio (Sr) and contrast ratios (Cr) were quantitatively evaluated. STATISTICAL TESTS: Wilcoxon signed rank test for visual scores, paired t-test for continuous variables, significance at P < 0.05. RESULTS: The distance between apex and the right hemidiaphragmatic dome was significantly larger (P < 0.001) with UTE-HF-NIV compared with UTE-FB and VIBE acquisitions. Vessel and airway visibility had identical median visual scores with all UTE methods. Median visual scores for sharpness of vessels and airways were significantly higher (P < 0.001) with HF-NIV (vessels = 3; airways = 2) than in UTE-FB (vessels = 2; airways = 1) and VIBE (vessels = 1; airways = 1). Software-based vessel sharpness evaluation resulted in larger values in 8/10 volunteers with UTE-HF-NIV (67.3 ± 9.8) compared with UTE-Avg (62.3 ± 12.6) but the average difference was not significant (P = 0.28). The sharpness of the lung-liver interface was significantly higher (P < 0.001) with HF-NIV (17.3 ± 5.3) compared with UTE-Avg (14.1 ± 3.9). Significantly higher values (P < 0.01) of Sr and Cr were observed with UTE-HF-NIV compared with UTE-FB and VIBE. DATA CONCLUSION: HF-NIV allowing acquisition at full inspiration significantly improves image quality for lung imaging. This could offer the option to alternate some follow-up CT studies by using this technique. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;50:1789-1797.

Probing the intravascular and interstitial compartments of remodeled myocardium in heart failure patients with preserved and reduced ejection fraction: a CMR study.

BACKGROUND: Recent autopsy studies found microvascular rarefaction in remodeled myocardium of patients who died of heart failure with preserved ejection-fraction (HFpEF). This condition has not been investigated so far by non-invasive methods in patients with HFpEF. The aim was to quantify the intravascular volume (IVV) compartment by CMR in HFpEF patients. METHODS: In two separate CMR examinations, HFpEF patients (n = 6; 12 examinations) and post-myocardial infarction patients (post-MI; n = 6; 12 examinations) were studied with T1-mapping (MOLLI-sequence) before and after IV bolus of 0.03 mmol/Kg of the intravascular contrast-medium (CM) Gadofosveset and 0.2 mmol/Kg of the extravascular CM Gadobutrol yielding IVV and extracellular volume (ECV), respectively. Healthy controls (n = 10 with Gadofosveset only, n = 10 with Gadobutrol only) were also studied with the same protocol. IVV and ECV were measured in the basal septum (without ischemic scar in post-MI patients). In post-MI patients, ECV and IVV were also measured in the ischemic scar. Left ventricular (LV) volumes, mass, and ejection-fraction were measured by standard protocol. LV global longitudinal strain (GLS) was calculated by feature tracking on long-axis cine acquisitions. RESULTS: LV mass to end-diastolic volume ratio and GLS in HFpEF were higher and lower, respectively, than in healthy controls and post-MI patients, whereas the post-MI patients showed lower LV ejection-fraction. Compared to healthy myocardium of controls, IVV in scar was reduced (0.135 ± 0.018 vs 0.109 ± 0.008, respectively, p = 0.005), while ECV was increased (0.244 ± 0.037 vs 0.698 ± 0.106, respectively, p < 0.001). However, IVV did not differ among HFpEF, post-MI, and healthy controls (0.155 ± 0.033, 0.146 ± 0.038, and 0.135 ± 0.018, respectively, p = 0.413), whereas ECV was higher in HFpEF than in post-MI and healthy controls (0.304 ± 0.159, 0.270 ± 0.017, and 0.244 ± 0.037, respectively, p = 0.003). CONCLUSIONS: The T1-mapping technique combined with an intravascular CM shows potential to measure IVV. In infarct scar with substantially increased ECV, IVV was significantly reduced. Unlike in infarct scar, in remodeled myocardium of HFpEF patients, increased ECV was not accompanied by a reduction of IVV.

Author Correction: Fetal cardiac cine magnetic resonance imaging in utero.

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Fetal cardiac cine magnetic resonance imaging in utero.

Fast magnetic resonance imaging (MRI) led to the emergence of 'cine MRI' techniques, which enable the visualization of the beating heart and the assessment of cardiac morphology and dynamics. However, established cine MRI methods are not suitable for fetal heart imaging in utero, where anatomical structures are considerably smaller and recording an electrocardiogram signal for synchronizing MRI data acquisition is difficult. Here we present a framework to overcome these challenges. We use methods for image acquisition and reconstruction that robustly produce images with sufficient spatial and temporal resolution to detect the heart contractions of the fetus, enabling a retrospective gating of the images and thus the generation of images of the beating heart. To underline the potential of our approach, we acquired in utero images in six pregnant patients and compared these with their echocardiograms. We found good agreement in terms of diameter and area measurements, and low inter- and intra- observer variability. These results establish MRI as a reliable modality for fetal cardiac imaging, with a substantial potential for prenatal evaluation of congenital heart defects.

Chest-MRI under pulsatile flow ventilation: A new promising technique.

OBJECTIVES: Magnetic resonance imaging (MRI) of the chest has long suffered from its sensitivity to respiratory and cardiac motion with an intrinsically low signal to noise ratio and a limited spatial resolution. The purpose of this study was to perform chest MRI under an adapted non invasive pulsatile flow ventilation system (high frequency percussive ventilation, HFPV®) allowing breath hold durations 10 to 15 times longer than other existing systems. METHODS: One volunteer and one patient known for a thymic lesion underwent a chest MRI under ventilation percussion technique (VP-MR). Routinely used sequences were performed with and without the device during three sets of apnoea on inspiration. RESULTS: VP-MR was well tolerated in both cases. The mean duration of the thoracic stabilization was 10.5 min (range 8.5-12) and 5.8 min (range 5-6.2) for Volunteer 1 and Patient 1, respectively. An overall increased image quality was seen under VP-MR with a better delineation of the mediastinal lesion for Patient 1. Nodules discovered in Volunteer 1 were confirmed with low dose CT. CONCLUSION: VP-MR was feasible and increased spatial resolution of chest MRI by allowing acquisition at full inspiration during thoracic stabilization approaching prolonged apnoea. This new technique could be of benefit to numerous thoracic disorders.

Current artefacts in cardiac and chest magnetic resonance imaging: tips and tricks.

Currently MRI is extensively used for the evaluation of cardiovascular and thoracic disorders because of the well-established advantages that include use of non-ionizing radiation, good contrast and high spatial resolution. Despite the advantages of this technique, numerous categories of artefacts are frequently encountered. They may be related to the scanner hardware or software functionalities, environmental factors or the human body itself. In particular, some artefacts may be exacerbated with high-field-strength MR machines (e.g. 3 T). Cardiac imaging poses specific challenges with respect to breath-holding and cardiac motion. In addition, new cardiac MR-conditional devices may also be responsible for peculiar artefacts. The image quality may thus be impaired and give rise to a misdiagnosis. Knowledge of acquisition and reconstruction techniques is required to understand and recognize the nature of these artefacts. This article will focus on the origin and appearance of the most common artefacts encountered in cardiac and chest MRI along with possible correcting methods to avoid or reduce them.