Jie Xiang, Rajiv Ramasawmy, Felicia Seemann, Dana C Peters, Adrienne E Campbell-Washburn
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引用次数: 0
Abstract
Background: There is a growing interest in the development and application of mid-field (0.55T) for cardiovascular magnetic resonance (CMR), including flow imaging. However, aortic flow imaging at 0.55T has limited signal-to-noise ratio (SNR), especially in diastolic phases where there is reduced inflow-driven contrast for spoiled gradient recalled echo (GRE) sequences. The low SNR can limit the accuracy of flow and regurgitant fraction measurements.
Methods: In this work, we developed a two-dimensional phase contrast (PC) acquisition with balanced steady-state free precession (bSSFP), termed PC-SSFP, for flow imaging and quantification at 0.55T. This PC-SSFP approach precisely nulls the zeroth and first gradient moments at both the echo time (TE) and repetition time, except for the flow-encoded acquisition, for which the first gradient moment at the TE is determined by the velocity encoding. Our proposed sequence was tested in both phantoms and in healthy volunteers (n = 11), to measure aortic flow. In volunteers, both a breath-hold (bh) and a free-breathing (fb) protocol, with averaging to increase SNR, were obtained. Total flow, peak flow, cardiac output, and SNR were compared for PC-SSFP and PC-GRE. Stroke volumes were also measured and compared to planimetry method.
Results: In a phantom, SNR was significantly higher using PC-SSFP compared to PC-GRE (25.5 ± 9.6 vs 8.2 ± 2.9), and the velocity measurements agreed well (R = 1.00). In healthy subjects, for both bh and fb protocols, PC-SSFP measured accurate peak flow (fb: R = 0.99, bh: R = 0.96) and cardiac output (fb: R = 0.98, bh: R = 0.88), compared to PC-GRE, accurate stroke volume (fb: R = 0.94, bh: R = 0.97), compared to planimetry measurement, and offered constant high SNR (fb: 28 ± 9 vs 18 ± 6, bh: 24 ± 7 vs 11 ± 3) over the cardiac cycle in 11 subjects.
Conclusion: PC-SSFP is a more reliable evaluation tool for aortic flow quantification, when compared to the conventional PC-GRE method at 0.55T, providing higher SNR, and thus potentially more accurate flows.
期刊介绍:
Journal of Cardiovascular Magnetic Resonance (JCMR) publishes high-quality articles on all aspects of basic, translational and clinical research on the design, development, manufacture, and evaluation of cardiovascular magnetic resonance (CMR) methods applied to the cardiovascular system. Topical areas include, but are not limited to:
New applications of magnetic resonance to improve the diagnostic strategies, risk stratification, characterization and management of diseases affecting the cardiovascular system.
New methods to enhance or accelerate image acquisition and data analysis.
Results of multicenter, or larger single-center studies that provide insight into the utility of CMR.
Basic biological perceptions derived by CMR methods.