Browsing by Author "Si, Dongyue"

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    3D Whole‐Heart Joint T1/T1ρ Mapping and Water‐Fat Imaging on a Clinical 0.55‐T Low‐Field Scanner
    (2026) Crabb, Michael G.; Kunze, Karl P.; Castillo Passi, Carlos; Si, Dongyue; Littlewood, Simon J.; Prieto Vásquez, Claudia; Botnar, Rene Michael
    Myocardial maps are conventionally acquired in 2D breath-hold single-parameter scans that are slow and have limited heart coverage. To overcome limitations associated with 2D breath-hold mapping sequences, we develop a novel free-breathing 3D joint T₁ / T₁ρ mapping sequence with Dixon encoding to provide co-registered 3D T₁ and T₁ρ maps and water-fat volumes with isotropic spatial resolution in a single scan for comprehensive contrast-agent free myocardial tissue characterization and visualization of the whole-heart anatomy on a clinical 0.55-T MR scanner. The proposed sequence acquires four interleaved 3D volumes with preparation modules to provide T₁ and T₁ρ encoding, with data acquired with a two-echo Dixon readout and 2D image navigators to enable 100% respiratory scan efficiency. Images were reconstructed with nonrigid respiratory motion-corrected iterative SENSE with multi-dimensional low-rank patch-based denoising, and maps generated by matching with simulated dictionaries. The proposed sequence was tested in phantoms, 11 healthy subjects and 1 patient, and compared with conventional techniques. For phantoms, the proposed 3D T₁ and T₁ρ measurements showed good correlation with 2D spin-echo reference measurements. For healthy subjects, septal myocardial tissue mapping values were T₁ = 743 ± 19 ms and T₁ρ = 46.9 ± 2.7 ms for the proposed sequence, against T₁ = 681 ± 23 ms and T₁ρ = 57.9 ± 3.6 ms for 2D modified Look-Locker inversion recovery and 2D T₁ρ, respectively. Promising results were obtained when the proposed mapping was compared to 2D late-gadolinium enhancement imaging in a patient. The proposed approach enables simultaneous 3D whole-heart joint T₁ / T₁ρ mapping and water-fat imaging at 0.55 T in a single scan of ≈ 11 min, demonstrating good agreement with conventional techniques in phantoms and healthy subjects, and promising results in a patient.
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    Cardiovascular magnetic resonance imaging: Principles and advanced techniques
    (2025) Si, Dongyue; Littlewood, Simon J.; Crabb, Michael G.; Phair, Andrew; Prieto Vásquez, Claudia; Botnar, René Michael
    Cardiovascular magnetic resonance (CMR) imaging is an established non-invasive tool for the assessment of cardiovascular diseases, which are the leading cause of death globally. CMR provides dynamic and static multi-contrast and multi-parametric images, including cine for functional evaluation, contrast-enhanced imaging and parametric mapping for tissue characterization, and MR angiography for the assessment of the aortic, coronary and pulmonary circulation. However, clinical CMR imaging sequences still have some limitations such as the requirement for multiple breath-holds, incomplete spatial coverage, complex planning and acquisition, low scan efficiency and long scan times. To address these challenges, novel techniques have been developed during the last two decades, focusing on automated planning and acquisition timing, improved respiratory and cardiac motion handling strategies, image acceleration algorithms employing undersampled reconstruction, all-in-one imaging techniques that can acquire multiple contrast/parameters in a single scan, deep learning based methods applied along the entire CMR imaging pipeline, as well as imaging at high- and low-field strengths. In this article, we aim to provide a comprehensive review of CMR imaging, covering both established and emerging techniques, to give an overview of the present and future applications of CMR.
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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