Browsing by Author "Crabb, Michael G."

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    3D joint T 1/T 1 ρ/T 2 mapping and water-fat imaging for contrast-agent free myocardial tissue characterization at 1.5T.
    (2025) Crabb, Michael G.; Kunze, Karl P.; Littlewood, Simon J.; Tripp, Donovan; Fotaki, Anastasia; Prieto Vásquez, Claudia; Botnar, René Michael
    PURPOSE: To develop a novel, free-breathing, 3D joint T 1 $$ {T}_1 $$ / T 1 ρ $$ {T}_{1\rho } $$ / T 2 $$ {T}_2 $$ mapping sequence with Dixon encoding to provide co-registered 3D T 1 $$ {T}_1 $$ , T 1 ρ $$ {T}_{1\rho } $$ , and T 2 $$ {T}_2 $$ maps and water-fat volumes with isotropic spatial resolution in a single ≈ 7 $$ \approx 7 $$ min scan for comprehensive contrast-agent-free myocardial tissue characterization and simultaneous evaluation of the whole-heart anatomy. METHODS: An interleaving sequence over 5 heartbeats is proposed to provide T 1 $$ {T}_1 $$ , T 1 ρ $$ {T}_{1\rho } $$ , and T 2 $$ {T}_2 $$ encoding, with 3D data acquired with Dixon gradient-echo readout and 2D image navigators to enable 100 % $$ 100\% $$ respiratory scan efficiency. Images were reconstructed with a non-rigid motion-corrected, low-rank patch-based reconstruction, and maps were generated through dictionary matching. The proposed sequence was compared against conventional 2D techniques in phantoms, 10 healthy subjects, and 1 patient. RESULTS: The proposed 3D T 1 $$ {T}_1 $$ , T 1 ρ $$ {T}_{1\rho } $$ , and T 2 $$ {T}_2 $$ measurements showed excellent correlation with 2D reference measurements in phantoms. For healthy subjects, the mapping values of septal myocardial tissue were T 1 = 1060 ± 48 ms $$ {T}_1=1060\pm 48\kern0.2778em \mathrm{ms} $$ , T 1 ρ = 48 . 1 ± 3 . 9 ms $$ {T}_{1\rho }=48.1\pm 3.9\kern0.2778em \mathrm{ms} $$ , and T 2 = 44 . 2 ± 3 . 2 ms $$ {T}_2=44.2\pm 3.2\kern0.2778em \mathrm{ms} $$ for the proposed sequence, against T 1 = 959 ± 15 ms $$ {T}_1=959\pm 15\kern0.2778em \mathrm{ms} $$ , T 1 ρ = 56 . 4 ± 1 . 9 ms $$ {T}_{1\rho }=56.4\pm 1.9\kern0.2778em \mathrm{ms} $$ , and T 2 = 47 . 3 ± 1 . 5 ms $$ {T}_2=47.3\pm 1.5\kern0.2778em \mathrm{ms} $$ for 2D MOLLI, 2D T 1 ρ $$ {T}_{1\rho } $$ -prep bSSFP and 2D T 2 $$ {T}_2 $$ -prep bSSFP, respectively. Promising results were obtained when comparing the proposed mapping to 2D references in 1 patient with active myocarditis. CONCLUSION: The proposed approach enables simultaneous 3D whole-heart joint T 1 $$ {T}_1 $$ / T 1 ρ $$ {T}_{1\rho } $$ / T 2 $$ {T}_2 $$ mapping and water/fat imaging in ≈ $$ \approx $$ 7 min scan time, demonstrating good agreement with conventional mapping techniques in phantoms and healthy subjects and promising results in 1 patient with suspected cardiovascular disease.
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    Free‐breathing 3D whole‐heart joint T1/T2 mapping and water/fat imaging at 0.55 T
    (2024) Si, Dongyue; Crabb, Michael G.; Kunze, Karl P.; Littlewood, Simon J.; Prieto Vasquez, Claudia Del Carmen; Botnar, René M.
    To develop and validate a highly efficient motion compensated free-breathingisotropic resolution 3D whole-heart joint T 1 /T2 mapping sequence with anatomicalwater/fat imaging at 0.55 T.Methods: The proposed sequence takes advantage of shorter T1 at 0.55 T to acquirethree interleaved water/fat volumes with inversion-recovery preparation, no prepara-tion, and T 2 preparation, respectively. Image navigators were used to facilitate nonrigidmotion-compensated image reconstruction. T1 and T2 maps were jointly calculated bya dictionary matching method. Validations were performed with simulation, phantom,and in vivo experiments on 10 healthy volunteers and 1 patient. The performance ofthe proposed sequence was compared with conventional 2D mapping sequences includ-ing modified Look-Locker inversion recovery and T2 -prepared balanced steady-SSFPsequence.Results: The proposed sequence has a good T1 and T2 encoding sensitivity in simula-tion, and excellent agreement with spin-echo reference T 1 and T2 values was observedin a standardized T1 /T2 phantom (R2 = 0.99). In vivo experiments provided good-qualityco-registered 3D whole-heart T1 and T2 maps with 2-mm isotropic resolution in ashort scan time of about 7 min. For healthy volunteers, left-ventricle T1 mean andSD measured by the proposed sequence were both comparable with those of modi-fied Look-Locker inversion recovery (640 ± 35 vs. 630 ± 25 ms [p = 0.44] and 49.9 ± 9.3vs. 54.4 ± 20.5 ms [p = 0.42]), whereas left-ventricle T2 mean and SD measured by theproposed sequence were both slightly lower than those of T2 -prepared balanced SSFP(53.8 ± 5.5 vs. 58.6 ± 3.3 ms [p < 0.01] and 5.2 ± 0.9 vs. 6.1 ± 0.8 ms [p = 0.03]). MyocardialT 1 and T2 in the patient measured by the proposed sequence were in good agreementwith conventional 2D sequences and late gadolinium enhancement.Conclusion: The proposed sequence simultaneously acquires 3D whole-heart T1 and T2mapping with anatomical water/fat imaging at 0.55 T in a fast and efficient 7-min scan.Further investigation in patients with cardiovascular disease is now warranted
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    Highly efficient image navigator based 3D whole-heart cardiac MRA at 0.55T
    (2024) Castillo-Passi, Carlos; Kunze, Karl P.; Crabb, Michael G.; Munoz, Camila; Fotaki, Anastasia; Neji, Radhouene; Irarrazaval, Pablo; Prieto, Claudia; Botnar, Rene M.
    PurposeTo develop and evaluate a highly efficient free-breathing and contrast-agent-free three-dimensional (3D) whole-heart Cardiac Magnetic Resonance Angiography (CMRA) sequence at 0.55T.MethodsFree-breathing whole-heart CMRA has been previously proposed at 1.5 and 3T. Direct application of this sequence to 0.55T is not possible due to changes in the magnetic properties of the tissues. To enable free-breathing CMRA at 0.55T, pulse sequence design and acquisition parameters of a previously proposed whole-heart CMRA framework are optimized via Bloch simulations. Image navigators (iNAVs) are used to enable nonrigid respiratory motion-correction and 100% respiratory scan efficiency. Patch-based low-rank denoising is employed to accelerate the scan and account for the reduced signal-to-noise ratio at 0.55T. The proposed approach was evaluated on 11 healthy subjects. Image quality was assessed by a clinical expert (1: poor to 5: excellent) for all intrapericardiac structures. Quantitative evaluation was performed by assessing the vessel sharpness of the proximal right coronary artery (RCA).ResultsOptimization resulted in an imaging flip angle of 110 degrees$$ 11{0}<^>{\circ } $$, fat saturation flip angle of 180 degrees$$ 18{0}<^>{\circ } $$, and six k-space lines for iNAV encoding. The relevant cardiac structures and main coronary arteries were visible in all subjects, with excellent image quality (mean 4.9/5.0$$ 4.9/5.0 $$) and minimal artifacts (mean 4.9/5.0$$ 4.9/5.0 $$), with RCA vessel sharpness (50.3%+/- 9.8%$$ 50.3\%\pm 9.8\% $$) comparable to previous studies at 1.5T.ConclusionThe proposed approach enables 3D whole-heart CMRA at 0.55T in a 6-min scan (5.9 +/- 0.7 min$$ 5.9\pm 0.7\;\min $$), providing excellent image quality, minimal artifacts, and comparable vessel sharpness to previous 1.5T studies. Future work will include the evaluation of the proposed approach in patients with cardiovascular disease.
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    Simultaneous 3D T1,T2, and fat-signal-fraction mapping with respiratory-motion correction for comprehensive liver tissue characterization at 0.55 T
    (2024) Tripp, Donovan P.; Kunze, Karl P.; Crabb, Michael G.; Prieto, Claudia; Neji, Radhouene; Botnar, Rene M.
    Purpose: To develop a framework for simultaneous three-dimensional (3D) mapping of T-1, T-2, and fat signal fraction in the liver at 0.55T. Methods: The proposed sequence acquires four interleaved 3D volumes with a two-echo Dixon readout. T-1 and T-2 are encoded into each volume via preparation modules, and dictionary matching allows simultaneous estimation of T-1, T-2, and M0 for water and fat separately. 2D image navigators permit respiratory binning, and motion fields from nonrigid registration between bins are used in a non rigid respiratory-motion-corrected reconstruction, enabling 100% scan efficiency from a free-breathingacquisition.Theintegratednatureoftheframeworkensures the resulting maps are always co-registered. Results: T-1, T-2, and fat-signal-fraction measurements in phantoms correlated strongly (adjusted r(2) > 0.98) with reference measurements. Mean liver tissue parameter values in 10 healthy volunteers were 427 +/- 22, 47.7 +/- 3.3ms, and 7 +/- 2% for T-1, T-2, and fat signal fraction, giving biases of 71,-30.0 ms, and -5 percentage points, respectively, when compared to conventional methods. Conclusion: A novel sequence for comprehensive characterization of liver tissue at 0.55T was developed. The sequence provides co-registered 3D T-1, T-2, and fat-signal-fraction maps with full coverage of the liver, from a single nine-and-a-half-minute free-breathing scan. Further development is needed to achieve accurate proton-density fat fraction (PDFF) estimation in vivo.