Dresselaers Tom, De Keyzer Frederik, Cernicanu Alexandru, Bogaert Jan, Gatehouse Peter
Department of Radiology, University Hospitals Leuven, Herestraat 49, 3000 Leuven, Belgium; Department of Imaging and Pathology, KU Leuven, Herestraat 49, 3000 Leuven, Belgium.
Department of Radiology, University Hospitals Leuven, Herestraat 49, 3000 Leuven, Belgium; Department of Imaging and Pathology, KU Leuven, Herestraat 49, 3000 Leuven, Belgium.
J Cardiovasc Magn Reson. 2025 May 8;27(2):101908. doi: 10.1016/j.jocmr.2025.101908.
Although balanced steady-state free-precession (bSSFP) cines provide excellent contrast for morpho-functional cardiac evaluation, the fluctuating myocardial cine signal intensity (mcSI) is rarely used diagnostically. These mcSI fluctuations were related to through-plane motion but the impact of this motion remains unclear. We aim to characterize the mid-ventricular pre- and postcontrast bSSFP cyclic mcSI fluctuations in healthy subjects and compare these to Bloch simulations incorporating through-plane motion.
Retrospectively-gated mid-ventricular short-axis cine bSSFP images from healthy subjects (n = 49) acquired at 1.5T pre- and early postcontrast were analyzed. First, the mcSI fluctuations during the heart cycle were determined and their timing compared to the radial myocardial motion. Next, pre- vs postcontrast differences were determined during systole, early-diastole, and late-diastole. Finally, Bloch simulations and acquisitions in a moving T1 phantom were performed to analyze the through-plane motion effect on the bSSFP and spoiled gradient echo (SGRE) mcSI.
The bSSFP mcSI showed a three-peak pattern both pre- and postcontrast, corresponding to the contraction and relaxation phases. However, the mcSI peaks showed a time lag vs the times of maximum radial velocity that was larger for the systolic contraction than for the early or late-diastolic relaxation phases. In addition, the shape and amplitude of the systolic and early diastolic mcSI peaks changed significantly post- vs precontrast. Bloch simulations showed an in-vivo-like (regional) three-peak signal profile and similar changes for post- vs precontrast T1 levels. Finally, results in the moving phantom and accompanying simulations confirmed a slice-thickness-dependent time lag between the motion and mcSI profile in both bSSFP and SGRE.
In healthy subjects before and after contrast, the bSSFP mcSI variation during the heart cycle is characterized by a three-peak pattern associated with the contraction and relaxation phases. However, the delays in timing of these peaks vs the myocardial motion, as well as the differences between pre- and postcontrast, vary with the stage of the heart cycle. Bloch simulations suggest that these mcSI fluctuations are largely determined by the regional through-slice motion. A better understanding of these motion-induced contrast mechanisms may be beneficial to methods exploiting bSSFP mcSI.
尽管平衡稳态自由进动（bSSFP）电影成像为形态功能心脏评估提供了出色的对比度，但波动的心肌电影信号强度（mcSI）很少用于诊断。这些mcSI波动与层面内运动有关，但这种运动的影响仍不清楚。我们旨在描述健康受试者心室中部对比剂注射前后bSSFP周期性mcSI波动特征，并将其与纳入层面内运动的布洛赫模拟结果进行比较。
对49名健康受试者在1.5T场强下采集的回顾性门控心室中部短轴电影bSSFP图像进行分析，分别在注射对比剂前和早期注射后采集。首先，确定心动周期中的mcSI波动，并将其时间与径向心肌运动进行比较。其次，确定收缩期、舒张早期和舒张晚期对比剂注射前后的差异。最后，进行布洛赫模拟并在移动的T1模型中采集数据，以分析层面内运动对bSSFP和扰相梯度回波（SGRE）mcSI的影响。
bSSFP mcSI在对比剂注射前后均呈现三峰模式，对应于收缩期和舒张期。然而，mcSI峰值相对于最大径向速度时间存在时间滞后，收缩期收缩的时间滞后大于舒张早期或舒张晚期的舒张期。此外，收缩期和舒张早期mcSI峰值的形状和幅度在对比剂注射后与注射前相比有显著变化。布洛赫模拟显示出类似体内的（区域）三峰信号分布，以及对比剂注射后与注射前T1水平的类似变化。最后，移动模型和伴随模拟的结果证实，在bSSFP和SGRE中，运动与mcSI分布之间存在与切片厚度相关的时间滞后。
在健康受试者对比剂注射前后，心动周期中bSSFP mcSI变化的特征是与收缩期和舒张期相关的三峰模式。然而，这些峰值相对于心肌运动的时间延迟以及对比剂注射前后的差异随心动周期阶段而变化。布洛赫模拟表明，这些mcSI波动在很大程度上由区域层面内运动决定。更好地理解这些运动诱导的对比机制可能对利用bSSFP mcSI的方法有益。
