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International audience; Background: Cardiac MRI features are not well-defined in immune checkpoint inhibitor (ICI)-induced myocarditis (ICI-M), a severe complication of ICI therapy in patients with cancer.Purpose: To analyze the cardiac MRI features of ICI-M and to explore their prognostic value in major adverse cardiovascular events (MACE).Materials and Methods: In this retrospective study from May 2017 to January 2020, cardiac MRI findings (including late gadolinium enhancement [LGE], T1 and T2 mapping, and extracellular volume fraction [ECV] z scores) of patients with ICI-M were compared with those of patients with cancer scheduled to receive ICI therapy (pre-ICI group) and patients with viral myocarditis. As a secondary objective, the potential value of cardiac MRI for predicting MACE in patients with ICI-M by using Cox proportional hazards models was explored.Results: Thirty-three patients with ICI-M (mean age +/- standard deviation, 68 years +/- 14; 23 men) were compared with 21 patients scheduled to receive to ICI therapy (mean age, 65 years +/- 14; 14 men) and 85 patients with viral myocarditis (mean age, 32 years +/- 13; 67 men). Compared with the pre-ICI group, patients with ICI-M showed higher global native T1, ECV, and T2 z scores (0.03 +/- 0.85 vs 1.79 +/- 1.93 [P < .001]; 1.34 +/- 0.57 vs 2.59 +/- 1.97 [P = .03]; and -0.76 +/- 1.41 vs 0.88 +/- 1.96 [P = .002], respectively), and LGE was more frequently observed (27 of 33 patients [82%] vs two of 21 [10%]; P < .001). LGE was less frequent in patients with ICI-M than those with viral myocarditis (27 of 33 patients [82%] vs 85 of 85 [100%]; P < .001) but was more likely to involve the septal segments (16 of 33 patients [48%] vs 25 of 85 [29%]; P < .001) and midwall layer (11 of 33 patients [33%] vs two of 85 [2%]; P < .001). Septal LGE was the only cardiac MRI predictor of MACE at 1 year even after adjustment for peak troponin (adjusted hazard ratio, 2.7 [95% CI: 1.1, 6.7]; P = .03).Conclusion: Cardiac MRI features of immune checkpoint inhibitor (ICI)-induced myocarditis (ICI-M) seem to differ from those in patients scheduled to receive ICIs and patients with viral myocarditis. Septal late gadolinium enhancement might be a predictor of major cardiovascular events in patients with ICI-M.

Objective. The aim of this work was to highlight and characterize a systemic ‘star-like’ artefact inherent to the low field 0.35 T MRIdian MR-linac system, a magnetic resonance guided radiotherapy device. This artefact is induced by the original split gradients coils design. This design causes a surjection of the intensity gradient in Z (or head-feet) direction. This artefact appears on every sequence with phase encoding in the head-feet direction. Approach. Basic gradient echo sequence and clinical mandatory bSSFP sequence were used. Three setups using manufacturer provided QA phantoms were designed: two including the linearity control grid used for the characterisation and a third including two homogeneity control spheres dedicated to the artefact management in a more clinical like situation. The presence of the artefact was checked in four different MRidian sites. The tested parameters based on the literature were: phase encoding orientation, slab selectivity, excitation bandwidth (BWRF), acceleration factor (R) and phase/slab oversampling (PO/SO). Main results. The position of this artefact is constant and reproducible over the tested MRIdian sites. The typical singularity saturated dot or star is visible even with the 3D slab-selection enabled. A management is proposed by decreasing the BWRF, the R in head-feet direction and increasing the PO/SO. The oversampling can be optimized using a formula to anticipate the location of artefact in the field of view. Significance. The star-like artefact has been well characterised. A manageable solution comes at the cost of acquisition time. Observed in clinical cases, the artefact may degrade the images used for the RT planning and repositioning during the treatment unless corrected.

Purpose To capture the multiquantum coherence (MQC) 23 Na signal. Different phase-cycling options and sequences are compared in a unified theoretical layout, and a novel sequence is developed. Methods An open source simulation overview is provided with graphical explanations to facilitate MQC understanding and access to techniques. Biases such as B0 inhomogeneity and stimulated echo signal were simulated for 4 different phase-cycling options previously described. Considerations for efficiency and accuracy lead to the implementation of a 2D Cartesian single and triple quantum imaging of sodium (CRISTINA) sequence employing two 6-step cycles in combination with a multi-echo readout. CRISTINA was compared to simultaneous single-quantum and triple-quantum-filtered MRI of sodium (SISTINA) under strong static magnetic gradient. CRISTINA capabilities were assessed on 8 × 60 mL, 0% to 5% agarose phantom with 50 to 154 mM 23 Na concentration at 7 T. CRISTINA was demonstrated subsequently in vivo in the brain. Results Simulation of B0 inhomogeneity showed severe signal dropout, which can lead to erroneous MQC measurement. Stimulated echo signal was highest at the time of triple-quantum coherences signal maximum. However, stimulated echo signal is separated by Fourier Transform as an offset and did not interfere with MQC signals. The multi-echo readout enabled capturing both single-quantum coherences and triple-quantum coherences signal evolution at once. Signal combination of 2 phase-cycles with a corresponding B0 map was found to recover the signal optimally. Experimental results confirm and complement the simulations. Conclusion Considerations for efficient MQC measurements, most importantly avoiding B0 signal loss, led to the design of CRISTINA. CRISTINA captures triple-quantum coherences and single-quantum coherences signal evolution to provide complete sodium signal characterization including T 2 ∗ fast, T 2 ∗ slow, MQC amplitudes, and sodium concentration.

To comparatively assess the performance of highly selective pulses computed with the SLR algorithm in fast-spin echo (FSE) within the current radiofrequency safety limits using a metamaterial-based coil for wrist magnetic resonance imaging. Apodized SINC pulses commonly used for clinical FSE sequences were considered as a reference. Selective SLR pulses with a time-bandwidth product of four were constructed in the MATPULSE program. Slice selection profiles in conventional T1-weighted and PD-weighted FSE wrist imaging pulse sequences were modeled using a Bloch equations simulator. Signal evolution was assessed in three samples with relaxation times equivalent to those in musculoskeletal tissues at 1.5T. Regular and SLR-based FSE pulse sequences were tested in a phantom experiment in a multi-slice mode with different gaps between slices and the direct saturation effect was investigated. As compared to the regular FSEs with a conventional transmit coil, combining the utilization of the metadevice with SLR-based FSEs provided a 23 times lower energy deposition in a duty cycle. When the slice gap was decreased from 100 to 0%, the “slice cross-talk” effect reduced the signal intensity by 15.9–17.6% in the SLR-based and by 22.9–32.3% in the regular T1-weighted FSE; and by 0.0–6.4% in the SLR-based and by 0.3–9.3% in the regular PD-weighted FSE. SLR-based FSE together with the metadevice allowed to increase the slice selectivity while still being within the safe SAR limits. The “slice cross-talk” effects were conditioned by the number of echoes in the echo train, the repetition time, and T1 relaxation times. The approach was more beneficial for T1-weighted SLR-based FSE as compared to PD-weighted. The combination of the metadevice and SLR-based FSE offers a promising alternative for MR investigations that require scanning in a “Low-SAR” regime such as those for children, pregnant women, and patients with implanted devices.

Background Single-voxel proton cardiovascular magnetic resonance spectroscopy (1H-CMRS) benefits from 3 T to detect metabolic abnormalities with the quantification of intramyocardial fatty acids (FA) and creatine (Cr). Conventional point resolved spectroscopy (PRESS) sequence remains the preferred choice for CMRS, despite its chemical shift displacement error (CSDE) at high field (≥ 3 T). Alternative candidate sequences are the semi-adiabatic Localization by Adiabatic SElective Refocusing (sLASER) recommended for brain and musculoskeletal applications and the localized stimulated echo acquisition mode (STEAM). In this study, we aim to compare these three single-voxel 1H-CMRS techniques: PRESS, sLASER and STEAM for reproducible quantification of myocardial FA and Cr at 3 T. Sequences are compared both using breath-hold (BH) and free-breathing (FB) acquisitions. Methods CMRS accuracy and theoretical CSDE were verified on a purposely-designed fat–water phantom. FA and Cr CMRS data quality and reliability were evaluated in the interventricular septum of 10 healthy subjects, comparing repeated BH and free-breathing with retrospective gating. Results Measured FA/W ratio deviated from expected phantom ratio due to CSDE with all sequences. sLASER supplied the lowest bias (10%, vs -28% and 27% for PRESS and STEAM). In vivo, PRESS provided the highest signal-to-noise ratio (SNR) in FB scans (27.5 for Cr and 103.2 for FA). Nevertheless, a linear regression analysis between the two BH showed a better correlation between myocardial Cr content measured with sLASER compared to PRESS (r = 0.46; p = 0.03 vs. r = 0.35; p = 0.07) and similar slopes of regression lines for FA measurements (r = 0.94; p Conclusion When quantifying myocardial lipids and creatine with CMR proton spectroscopy at 3 T, PRESS provided higher SNR, while sLASER was more reproducible both with single BH and FB scans.

International audience; Cardiac perfusion MRI is proving to be a valuable noninvasive assessment tool in the armamentarium for patients with suspected coronary artery disease or microvascular disease, both for initial diagnosis and for follow-up to therapeutic decision. In particular, it has recently been shown to be comparable and more cost-effective than invasive fractional flow reserve for therapeutic guidance of patients with suspected CAD 1. This is especially true since the long-awaited results of the ISCHEMIA study challenge invasive management of coronary artery disease and demonstrate the value of optimal medical treatment 2. The Orbita study also masterfully demonstrated that an invasive approach is not the ultimate solution to propose to symptomatic coronary patients 3. In this context of decreasing radicality and slowing down of the therapeutic approach with an increasing role of an optimized medical approach, it is clear that dynamic cardiac perfusion MRI with contrast imaging therefore promises to become the cornerstone of regular follow-up that will be proposed in future guidelines.

Purpose To measure multi-quantum coherence (MQC) 23Na signals for noninvasive cell physiological information in the whole-brain, the 2D-CRISTINA method was extended to 3D. This experimental study investigated the use and results of a new sequence, 3D-CRISTINA, on a phantom and healthy volunteers. Methods The 3D Cartesian single and triple-quantum imaging of 23Na (3D-CRISTINA) was developed and implemented at 7T, favoring a non-selective volume excitation for increased signal-to-noise ratio (SNR) and lower energy deployment than its 2D counterpart. Two independent phase cycles were used in analogy to the 2D method. A comparison of 6-steps cycles and 12-steps cycles was performed. We used a phantom composed of different sodium and agarose concentrations, 50 mM to 150 mM Na+, and 0–5% agarose for sequence validation. Four healthy volunteers were scanned at 7T for whole brain MQC imaging. The sequence 3D-CRISTINA was developed and tested at 7T. Results At 7T, the 3D-CRISTINA acquisition allowed to reduce the TR to 230 ms from the previous 390 ms for 2D, resulting in a total acquisition time of 53 min for a 3D volume of 4 × 4 × 8 mm resolution. The phase cycle evaluation showed that the 7T acquisition time could be reduced by 4-fold with moderate single and triple-quantum signals SNR loss. The healthy volunteers demonstrated clinical feasibility at 7T and showed a difference in the MQC signals ratio of White Matter (WM) and Grey Matter (GM). Conclusion Volumetric CRISTINA multi-quantum imaging allowed whole-brain coverage. The non-selective excitation enabled a faster scan due to a decrease in energy deposition which enabled a lower repetition time. Thus, it should be the preferred choice for future in vivo multi-quantum applications compared to the 2D method. A more extensive study is warranted to explore WM and GM MQC differences.

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To measure multi-quantum coherence (MQC)The 3D Cartesian single and triple-quantum imaging ofAt 7T, the 3D-CRISTINA acquisition allowed to reduce the TR to 230ms from the previous 390ms for 2D, resulting in a total acquisition time of 53min for a 3D volume of 4×4×8mm resolution. The phase cycle evaluation showed that the 7T acquisition time could be reduced by 4-fold with moderate single and triple-quantum signals SNR loss. The healthy volunteers demonstrated clinical feasibility at 7T and showed a difference in the MQC signals ratio of White Matter (WM) and Grey Matter (GM).Volumetric CRISTINA multi-quantum imaging allowed whole-brain coverage. The non-selective excitation enabled a faster scan due to a decrease in energy deposition which enabled a lower repetition time. Thus, it should be the preferred choice for future in vivo multi-quantum applications compared to the 2D method. A more extensive study is warranted to explore WM and GM MQC differences.

To comparatively assess the performance of highly selective pulses computed with the SLR algorithm in fast-spin echo (FSE) within the current radiofrequency safety limits using a metamaterial-based coil for wrist magnetic resonance imaging.Apodized SINC pulses commonly used for clinical FSE sequences were considered as a reference. Selective SLR pulses with a time-bandwidth product of four were constructed in the MATPULSE program. Slice selection profiles in conventional T1-weighted and PD-weighted FSE wrist imaging pulse sequences were modeled using a Bloch equations simulator. Signal evolution was assessed in three samples with relaxation times equivalent to those in musculoskeletal tissues at 1.5T. Regular and SLR-based FSE pulse sequences were tested in a phantom experiment in a multi-slice mode with different gaps between slices and the direct saturation effect was investigated.As compared to the regular FSEs with a conventional transmit coil, combining the utilization of the metadevice with SLR-based FSEs provided a 23 times lower energy deposition in a duty cycle. When the slice gap was decreased from 100 to 0%, the "slice cross-talk" effect reduced the signal intensity by 15.9-17.6% in the SLR-based and by 22.9-32.3% in the regular T1-weighted FSE; and by 0.0-6.4% in the SLR-based and by 0.3-9.3% in the regular PD-weighted FSE.SLR-based FSE together with the metadevice allowed to increase the slice selectivity while still being within the safe SAR limits. The "slice cross-talk" effects were conditioned by the number of echoes in the echo train, the repetition time, and T1 relaxation times. The approach was more beneficial for T1-weighted SLR-based FSE as compared to PD-weighted. The combination of the metadevice and SLR-based FSE offers a promising alternative for MR investigations that require scanning in a "Low-SAR" regime such as those for children, pregnant women, and patients with implanted devices.

Due to the wavelengths’ reduction in the human tissues at ultra-high field MRI, head coils usually present B$_{\mathbf{1}}^{\mathbf{+}}$ magnetic field inhomogeneities located at the brain’s temporal lobes. Different approaches have effectively targeted this problem, at the cost of either decrease the B$_{\mathbf{1}}^{\mathbf{+}}$ field in other regions or be uncomfortable to the patient. Here, we present a new approach based on Hilbert fractal inspired dipoles. Our structures improved simultaneously the B}$_{\mathbf{1}}^{\mathbf{+}}$ field in each temporal lobe without diminishing the B$_{\mathbf{1}}^{\mathbf{+}}$ field in other parts of the brain or the patients’ comfort.

International audience; B 1 + inhomogeneities in the temporal lobes of the brain are common while using a birdcage coil at 7T. Different approaches have effectively targeted this problem, at the cost of decreasing the B 1 + field in other important areas or being uncomfortable to the patient. Here, we present a new approach based on two resonant fractal metasurfaces. These fractal resonators improve simultaneously the B 1 + field in each temporal lobe without affecting the B 1 + field in other parts of the brain.

Purpose To compare the assessment of diffuse interstitial myocardial fibrosis in valvular diseases using cardiac magnetic resonance (CMR) extracellular volume fraction (ECV) quantification and serum biomarkers of collagen turnover using results of myocardial biopsy as standard of reference. Materials and methods This prospective monocentric study included consecutive patients before aortic valvular replacement. All patients underwent: i), 1.5 T CMR with pre and post contrast T1 mapping sequence and ECV computation; ii), serum quantification of matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs) and iii), myocardial biopsies were collected during surgery to assess collagen volume fraction (CVF). Patients with coronary artery disease were excluded. Correlation between native T1, ECV, CVF and serum biomarkers were assessed using Pearson correlation test. Agreement between basal anteroseptal ECV with global ECV was assessed using Bland-Altman test. Results Twenty-one patients, 16 with aortic stenosis and 5 with aortic regurgitation were included. There were 12 men and 9 women with a mean age of 74.1 ± 6.8 (SD) years (range: 32–84 years). Mean global ECV value was 26.7 ± 2.7 (SD) % (range: 23.4–32.5%) and mean CVF value was 12.4 ± 9.7% (range: 3.2–25.7%). ECV assessed at the basal anteroseptal segment correlated moderately with CVF (r = 0.6; P = 0.0026). There was a strong correlation and agreement between basal anteroseptal ECV and global ECV, (r = 0.8; P Conclusion In patients with severe aortic valvulopathy, diffuse myocardial fibrosis assessed by anterosepto-basal ECV correlates with histological myocardial fibrosis. Anteroseptobasal ECV strongly correlates with global ECV, which poorly correlates with TIMP-1 and MMP-2, serum biomarkers involved in the progression of heart failure.

Background This study evaluates the possibility for replacing conventional 3 slices, 3 breath-holds MOLLI cardiac T1 mapping with single breath-hold 3 simultaneous multi-slice (SMS3) T1 mapping using blipped-CAIPIRINHA SMS-bSSFP MOLLI sequence. As a major drawback, SMS-bSSFP presents unique artefacts arising from side-lobe slice excitations that are explained by imperfect RF modulation rendering and bSSFP low flip angle enhancement. Amplitude-only RF modulation (AM) is proposed to reduce these artefacts in SMS-MOLLI compared to conventional Wong multi-band RF modulation (WM). Materials and methods Phantoms and ten healthy volunteers were imaged at 1.5 T using a modified blipped-CAIPIRINHA SMS-bSSFP MOLLI sequence with 3 simultaneous slices. WM-SMS3 and AM-SMS3 were compared to conventional single-slice (SMS1) MOLLI. First, SNR degradation and T1 accuracy were measured in phantoms. Second, artefacts from side-lobe excitations were evaluated in a phantom designed to reproduce fat presence near the heart. Third, the occurrence of these artefacts was observed in volunteers, and their impact on T1 quantification was compared between WM-SMS3 and AM-SMS3 with conventional MOLLI as a reference. Results In the phantom, larger slice gaps and slice thicknesses yielded higher SNR. There was no significant difference of T1 values between conventional MOLLI and SMS3-MOLLI (both WM and AM). Positive banding artefacts were identified from fat neighbouring the targeted FOV due to side-lobe excitations from WM and the unique bSSFP signal profile. AM RF pulses reduced these artefacts by 38%. In healthy volunteers, AM-SMS3-MOLLI showed similar artefact reduction compared to WM-SMS3-MOLLI (3 ± 2 vs 5 ± 3 corrupted LV segments out of 16). In-vivo native T1 values obtained from conventional MOLLI and AM-SMS3-MOLLI were equivalent in LV myocardium (SMS1-T1 = 935.5 ± 36.1 ms; AM-SMS3-T1 = 933.8 ± 50.2 ms; P = 0.436) and LV blood pool (SMS1-T1 = 1475.4 ± 35.9 ms; AM-SMS3-T1 = 1452.5 ± 70.3 ms; P = 0.515). Identically, no differences were found between SMS1 and SMS3 postcontrast T1 values in the myocardium (SMS1-T1 = 556.0 ± 19.7 ms; SMS3-T1 = 521.3 ± 28.1 ms; P = 0.626) and the blood (SMS1-T1 = 478 ± 65.1 ms; AM-SMS3-T1 = 447.8 ± 81.5; P = 0.085). Conclusions Compared to WM RF modulation, AM SMS-bSSFP MOLLI was able to reduce side-lobe artefacts considerably, providing promising results to image the three levels of the heart in a single breath hold. However, few artefacts remained even using AM-SMS-bSSFP due to residual RF imperfections. The proposed blipped-CAIPIRINHA MOLLI T1 mapping sequence provides accurate in vivo T1 quantification in line with those obtained with a single slice acquisition.

Purpose To implement, characterize, and optimize an interleaved inhomogeneous magnetization transfer (ihMT) gradient echo sequence allowing for whole-brain imaging within a clinically compatible scan time. Theory and Methods A general framework for ihMT modelling was developed based on the Provotorov theory of radiofrequency saturation, which accounts for the dipolar order underpinning the ihMT effect. Experimental studies and numerical simulations were performed to characterize and optimize the ihMT-gradient echo dependency with sequence timings, saturation power, and offset frequency. The protocol was optimized in terms of maximum signal intensity and the reproducibility assessed for a nominal resolution of 1.5 mm isotropic. All experiments were performed on healthy volunteers at 1.5T. Results An important mechanism driving signal optimization and leading to strong ihMT signal enhancement that relies on the dynamics of radiofrequency energy deposition has been identified. By taking advantage of the delay allowed for readout between ihMT pulse bursts, it was possible to boost the ihMT signal by almost 2-fold compared to previous implementation. Reproducibility of the optimal protocol was very good, with an intra-individual error

Purpose To evaluate the feasibility and performance of compressed sensing (CS) with magnitude subtraction regularization in accelerating non–contrast-enhanced dynamic intracranial MR angiography (NCE-dMRA). Methods A CS algorithm was introduced in NCE-dMRA by exploiting the sparsity of the magnitude difference of the control and label images. The NCE-dMRA data were acquired using golden-angle stack-of-stars trajectory on six healthy volunteers and one patient with arteriovenous fistula. Images were reconstructed using (i) the proposed magnitude-subtraction CS (MS-CS); (ii) complex-subtraction CS; (iii) independent CS; and (iv) view-sharing with k-space weighted image contrast (KWIC). The dMRA image quality was compared across the four reconstruction strategies. The proposed MS-CS method was further compared with KWIC for temporal fidelity of depicting dynamic flow. Results The proposed MS-CS method was able to reconstruct NCE-dMRA images with detailed vascular structures and clean background. It provided better subjective image quality than the other two CS strategies (P

International audience; PurposeThe purpose of this prospective study was to assess the value of biventricular extracellular volume (ECV) in pre-capillary pulmonary hypertension (PH) obtained using cardiac magnetic resonance imaging (CMR) and to correlate ECV with markers of prognosis such as strain echocardiography and blood biomarkers of fibrosis.Materials and methodsTwelve patients with PH (6 men, 6 women; mean age = 50 ± 16 [SD] years; age range: 22–73 years) underwent the same day: (i), transthoracic echocardiography including measurement of right ventricular (RV) fractional shortening (RVfs), tricuspid annular plane systolic excursion (TAPSE), maximal tricuspid annular velocity, RV global and segmental deformation; (ii), right heart catheterization measuring pulmonary arterial pressures (in mmHg) and cardiac output (in L/min); (iii), CMR at 1.5-T measuring RV volumes and ejection fraction; (iv), native and 15 min post-contrast T1 mapping using modified look-locker inversion-recovery sequence; and (v), serum quantification of two biomarkers of collagen turnover and hematocrit. Non-parametric Mann-Whitney tests were used to search for differences between categorical variables. Spearman correlation test was used for search for correlation between quantitative values.ResultsGlobal RV ECV was 34% ± 4.2 (SD) for our entire population. A significant correlation was found between RV ECV and RVfs (r = 0.6; P = 0.026), S wave velocity (r = 0.7; P = 0.009), TAPSE (r = 0.6; P = 0.040) and RV systolic ejection fraction on CMR (r = 0.6; P = 0.04). There were no correlations between the ECV values in the lateral wall of the RV and in the septum (r = 0.4; P = 0.206). A significant correlation was found between septal ECV and 2D septal strain (r = 0.7; P = 0.013).ConclusionECV in PH as obtained using CMR appears to correlate with known echocardiographic prognostic markers and more specifically with the markers, which assess RV systolic function.

Background The axial motion of aortic root (AR) due to ventricular traction was previously suggested to contribute to ascending aorta (AA) dissection by increasing its longitudinal stress, but AR in-plane motion effects on stresses have never been studied. The objective is to investigate the contribution of AR in-plane motion to AA stress levels. Methods The AR in-plane motion was assessed on magnetic resonance imagining data from 25 healthy volunteers as the movement of the AA section centroid. The measured movement was prescribed to the proximal AA end of an aortic finite element model to investigate its influences on aortic stresses. The finite element model was developed from a patient-specific geometry using LS-DYNA solver and validated against the aortic distensibility. Fluid–structure interaction (FSI) approach was also used to simulate blood hydrodynamic effects on aortic dilation and stresses. Results The AR in-plane motion was 5.5 ± 1.7 mm with the components of 3.1 ± 1.5 mm along the direction of proximal descending aorta (PDA) to AA centroid and 3.0 ± 1.3 mm perpendicularly under the PDA reference system. The AR axial motion elevated the longitudinal stress of proximal AA by 40% while the corresponding increase due to in-plane motion was always below 5%. The stresses at proximal AA resulted approximately 7% less in FSI simulation with blood flow. Conclusions The AR in-plane motion was comparable with the magnitude of axial motion. Neither axial nor in-plane motion could directly lead to AA dissection. It is necessary to consider the heterogeneous pressures related to blood hydrodynamics when studying aortic wall stress levels. Electronic supplementary material The online version of this article (10.1186/s12938-019-0632-7) contains supplementary material, which is available to authorized users.

Purpose To capture the multiquantum coherence (MQC) 23Na signal. Different phase‐cycling options and sequences are compared in a unified theoretical layout, and a novel sequence is developed. Methods An open source simulation overview is provided with graphical explanations to facilitate MQC understanding and access to techniques. Biases such as B0 inhomogeneity and stimulated echo signal were simulated for 4 different phase‐cycling options previously described. Considerations for efficiency and accuracy lead to the implementation of a 2D Cartesian single and triple quantum imaging of sodium (CRISTINA) sequence employing two 6‐step cycles in combination with a multi‐echo readout. CRISTINA was compared to simultaneous single‐quantum and triple‐quantum‐filtered MRI of sodium (SISTINA) under strong static magnetic gradient. CRISTINA capabilities were assessed on 8 × 60 mL, 0% to 5% agarose phantom with 50 to 154 mM 23Na concentration at 7 T. CRISTINA was demonstrated subsequently in vivo in the brain. Results Simulation of B0 inhomogeneity showed severe signal dropout, which can lead to erroneous MQC measurement. Stimulated echo signal was highest at the time of triple‐quantum coherences signal maximum. However, stimulated echo signal is separated by Fourier Transform as an offset and did not interfere with MQC signals. The multi‐echo readout enabled capturing both single‐quantum coherences and triple‐quantum coherences signal evolution at once. Signal combination of 2 phase‐cycles with a corresponding B0 map was found to recover the signal optimally. Experimental results confirm and complement the simulations. Conclusion Considerations for efficient MQC measurements, most importantly avoiding B0 signal loss, led to the design of CRISTINA. CRISTINA captures triple‐quantum coherences and single‐quantum coherences signal evolution to provide complete sodium signal characterization including T2∗ fast, T2∗ slow, MQC amplitudes, and sodium concentration.

International audience; In the context of pelvic floor diseases understanding we advocate a process to observe the bladder over time in 3D. Thanks to multiplanar MRI acquisitions and adequate volume constructions, several volumes per seconds can show a bladder undergoing deformations under strain conditions. To our knowledge it is the first time such observation is performed. In addition we propose some deformation estimation clues that may be useful to pathology characterization and clinical diagnosis.

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International audience; To develop a Compressed Sensing (CS)-MP2RAGE sequence to drastically shorten acquisition duration and then detect and measure the T1 of brain metastases in mice at 7 T.METHODS:The encoding trajectory of the standard Cartesian MP2RAGE sequence has been modified (1) to obtain a variable density Poisson disk under-sampling distribution along the ky -kz plane, and (2) to sample the central part of the k-space exactly at TI1 and TI2 inversion times. In a prospective study, the accuracy of the T1 measurements was evaluated on phantoms containing increasing concentrations of gadolinium. The CS acceleration factors were increased to evaluate their influence on the contrast and T1 measurements of brain metastases in vivo. Finally, the 3D T1 maps were acquired with at 4-fold increased spatial resolution. The volumes and T1 values of the metastases were measured while using CS to reduce scan time.RESULTS:The implementation of the CS-encoding trajectory did not affect the T1 measurements in vitro. Accelerating the acquisition by a factor of 2 did not alter the contrast or the T1 values of the brain metastases. 3D T1 maps could be obtained in < 1 min using a CS factor of 6. Increasing the spatial resolution enabled more accurately measurement of the metastasis volumes while maintaining an acquisition duration below 5 min.CONCLUSION:The CS-MP2RAGE sequence could be of great interest in oncology to either rapidly obtain mouse brain 3D T1 maps or to increase the spatial resolution with no penalty on the scan duration.

International audience; PurposeTo accelerate cardiac cine at 7 tesla using simultaneous multi‐slice (SMS) acquisition with self‐calibration to resolve misalignment between calibration and imaging data due to breathing motion.MethodsA spoiled‐gradient echo cine sequence was modified with radiofrequency phase‐cycled SMS excitations. A Fourier encoding strategy was applied along the cardiac phase dimension to allow for slice untangling and split‐slice GRAPPA calibration. Split‐slice GRAPPA was coupled with regular GRAPPA (SMS‐GRAPPA) and L1‐SPIRiT (SMS‐L1SPIRiT) for image reconstruction. 3‐slice SMS cine MRI was evaluated in ten subjects against single‐slice cine MRI in terms of SNR and contrast‐to‐noise ratio and slice leakage.ResultsSNR decreased significantly from 10.1 ± 7.1 for single‐slice cine to 7.4 ± 2.8 for SMS‐GRAPPA (P = 0.02) and was recovered to 9.0 ± 4.5 with SMS‐L1SPIRiT (P = 0.02). Contrast to noise ratio decreased significantly from 14.5 ± 8.1 for single‐slice cine to 5.6 ± 3.6 for SMS‐GRAPPA (P < 0.0001) and increased slightly but significantly back to 6.7 ± 4.4 for SMS‐L1SPIRiT (P = 0.03). Specific absorption rate restrictions imposed a reduced nominal flip angle (−37 ± 7%, P = 0.02) for 3‐slice SMS excitations compared to single‐slice acquisitions. SMS slice leakage increased significantly from apex (8.6 ± 6.5 %) to base (13.1 ± 4.1 %, P = 0.03) in the left ventricle.ConclusionThree‐fold acceleration of cine at 7T was achieved using the proposed SMS technique. Fourier encoding self‐calibration and regularized image reconstruction enabled simultaneous acquisition of three slices without significant SNR decrease but significant CNR decrease linked to the reduced nominal excitation flip angle.

PURPOSE The purpose of this study was to quantify the distribution of trabeculated (T) and compact (C) left ventricular (LV) myocardium masses in a healthy Caucasian population against age, gender and LV parameters, and to provide normal values for T, C and T/C. MATERIALS AND METHODS One hundred and forty healthy subjects were prospectively recruited and underwent cardiac MRI at 1.5T with a stack of short-axis cine sequences covering the entire LV. End-diastolic volume (EDV), C and T masses were quantified using a semi-automatic method. Ejection fraction (EF) and T/C ratio were computed. RESULTS We included 70 men and 70 women with a mean age of 44±14 (SD) years (range: 20-69 years). The mean EF was 63.7±6.3 (SD) % (range: 50.7-82.0%), the mean EDV was 75.9±16.2 (SD) mL/m2 (range: 36.4-112.2mL/m2), the mean C mass was 53.9±11.2 (SD) g/m2 (range: 26.5-93.4g/m2) and the mean T mass was 4.9±2.4 (SD) g/m2 (range: 1.1-11.4g/m2). The T/C ratio was 9.2±4.5% (range: 2.0-29.4%). Multivariate ANOVA test showed that the compact mass was influenced by EDV (P