BackgroundThis 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 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 methodsPhantoms and ten healthy volunteers were imaged at 1.5T 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 obtained from conventional MOLLI and AM-SMS3-MOLLI were equivalent in LV myocardium (SMS1-T1=935.5±36.1ms; AM-SMS3-T1=933.8±50.2ms; P=0.436) and LV blood pool (SMS1-T1=1475.4±35.9ms; AM-SMS3-T1=1452.5±70.3ms; P=0.515). Identically, no differences were found between SMS1 and SMS3 postcontrast T1 values in the myocardium (SMS1-T1=556.0±19.7ms; SMS3-T1=521.3±28.1ms; P=0.626) and the blood (SMS1-T1= 478±65.1ms; AM-SMS3-T1=447.8±81.5; P=0.085). ConclusionsCompared 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.

BackgroundThe aim of our study was to evaluate the feasibility of exercise cardiac magnetic resonance (CMR) in patients with repaired tetralogy of Fallot (RTOF) and to assess right and left ventricular adaptation and aortic wall response to exercise in comparison with volunteers.Methods11 RTOF and 11 volunteers underwent prospective CMR at rest and during exercise. A supine bicycle ergometer was employed to reach twice the resting heart rate during continuous exercise, blood pressure and heart rate were recorded. Bi-ventricular parameters and aortic stiffness were assessed using accelerated cine sequences and flow-encoding CMR. A t-test was used to compare values between groups. A Mann Whitney test was used to compare values within groups.ResultsIn RTOF both ventricles showed an impaired contractile reserve (RVEF rest 36.2±8.3%, +1.3±3.9% increase after exercise; LVEF rest 53.8±6.1%, +5.7±6.4% increase after exercise) compared to volunteers (RVEF rest 50.5±5.0%, +10.4±7.1% increase after exercise, p = 0.039; LVEF rest 61.9±3.1%, +12.2±4.7% increase after exercise, p = 0.014).RTOF showed a reduced distensibility of the ascending aorta during exercise compared to volunteers (RTOF: 3.4±1.9 10-3.mmHg-1 vs volunteers: 5.1±1.4 10-3.mmHg-1; p = 0.027). Ascending aorta distensibility was correlated to cardiac work in the volunteers but not in RTOF.ConclusionRTOF showed an impaired contractile reserve for both ventricles. The exercise unmasked a reduced distensibility of the ascending aorta in RTOF, which may be an early sign of increased aortic rigidity.

Purpose To 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. Methods A 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. Results SNR 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. Conclusion Three‐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.

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