School of Biomedical Engineering and Imaging Sciences, King's College London, 3rd Floor, Lambeth Wing, St Thomas' Hospital, Lambeth Palace Rd, London, SE1 7EH, UK.
Siemens Healthcare, MR Research Collaborations, Frimley, UK.
J Cardiovasc Magn Reson. 2020 Feb 3;22(1):12. doi: 10.1186/s12968-020-0597-5.
Cardiovascular magnetic resonance (CMR) T1ρ mapping can be used to detect ischemic or non-ischemic cardiomyopathy without the need of exogenous contrast agents. Current 2D myocardial T1ρ mapping requires multiple breath-holds and provides limited coverage. Respiratory gating by diaphragmatic navigation has recently been exploited to enable free-breathing 3D T1ρ mapping, which, however, has low acquisition efficiency and may result in unpredictable and long scan times. This study aims to develop a fast respiratory motion-compensated 3D whole-heart myocardial T1ρ mapping technique with high spatial resolution and predictable scan time.
The proposed electrocardiogram (ECG)-triggered T1ρ mapping sequence is performed under free-breathing using an undersampled variable-density 3D Cartesian sampling with spiral-like order. Preparation pulses with different T1ρ spin-lock times are employed to acquire multiple T1ρ-weighted images. A saturation prepulse is played at the start of each heartbeat to reset the magnetization before T1ρ preparation. Image navigators are employed to enable beat-to-beat 2D translational respiratory motion correction of the heart for each T1ρ-weighted dataset, after which, 3D translational registration is performed to align all T1ρ-weighted volumes. Undersampled reconstruction is performed using a multi-contrast 3D patch-based low-rank algorithm. The accuracy of the proposed technique was tested in phantoms and in vivo in 11 healthy subjects in comparison with 2D T1ρ mapping. The feasibility of the proposed technique was further investigated in 3 patients with suspected cardiovascular disease. Breath-hold late-gadolinium enhanced (LGE) images were acquired in patients as reference for scar detection.
Phantoms results revealed that the proposed technique provided accurate T1ρ values over a wide range of simulated heart rates in comparison to a 2D T1ρ mapping reference. Homogeneous 3D T1ρ maps were obtained for healthy subjects, with septal T1ρ of 58.0 ± 4.1 ms which was comparable to 2D breath-hold measurements (57.6 ± 4.7 ms, P = 0.83). Myocardial scar was detected in 1 of the 3 patients, and increased T1ρ values (87.4 ± 5.7 ms) were observed in the infarcted region.
An accelerated free-breathing 3D whole-heart T1ρ mapping technique was developed with high respiratory scan efficiency and near-isotropic spatial resolution (1.7 × 1.7 × 2 mm) in a clinically feasible scan time of ~ 6 mins. Preliminary patient results suggest that the proposed technique may find applications in non-contrast myocardial tissue characterization.
心血管磁共振（CMR）T1ρ 映射可用于检测缺血性或非缺血性心肌病，而无需使用外源性对比剂。目前的二维心肌 T1ρ 映射需要多次屏气，并且提供的覆盖范围有限。最近，膈肌导航的呼吸门控已被用于实现自由呼吸的 3D T1ρ 映射，但这种方法采集效率低，可能导致不可预测且扫描时间长。本研究旨在开发一种快速的呼吸运动补偿的 3D 全心心肌 T1ρ 映射技术，具有高空间分辨率和可预测的扫描时间。
所提出的心电图（ECG）触发 T1ρ 映射序列是在自由呼吸下使用欠采样的可变密度 3D 笛卡尔采样和螺旋状顺序进行的。使用不同 T1ρ 自旋锁定时间的准备脉冲来获取多个 T1ρ 加权图像。在每个心跳开始时播放饱和预脉冲，以便在 T1ρ 准备之前重置磁化。图像导航器用于对每个 T1ρ 加权数据集进行逐拍 2D 平移呼吸运动校正，之后进行 3D 平移配准以对齐所有 T1ρ 加权体积。欠采样重建使用多对比度 3D 基于补丁的低秩算法进行。将所提出的技术在 11 名健康受试者的体模和体内进行了测试，并与 2D T1ρ 映射进行了比较。在 3 名疑似心血管疾病的患者中进一步研究了所提出技术的可行性。在患者中采集屏气晚期钆增强（LGE）图像作为疤痕检测的参考。
体模结果表明，与二维 T1ρ 映射参考相比，所提出的技术在模拟心率范围内提供了准确的 T1ρ 值。健康受试者获得了均匀的 3D T1ρ 图，中隔 T1ρ 值为 58.0 ± 4.1ms，与 2D 屏气测量值（57.6 ± 4.7ms，P=0.83）相当。在 3 名患者中的 1 名中检测到心肌疤痕，并且在梗死区域观察到升高的 T1ρ 值（87.4 ± 5.7ms）。
开发了一种加速的自由呼吸 3D 全心 T1ρ 映射技术，具有高呼吸扫描效率和近各向同性的空间分辨率（1.7 × 1.7 × 2mm），在临床可行的扫描时间约 6 分钟内完成。初步的患者结果表明，该技术可能在非对比心肌组织特征化中具有应用前景。
