BACKGROUND 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. METHODS 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. RESULTS 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. CONCLUSIONS 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 mm3) 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.

中文翻译：

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呼吸运动补偿的高分辨率3D全心T1ρ映射。

背景技术心血管磁共振（CMR）T1ρ作图可用于检测缺血性或非缺血性心肌病，而无需外源性造影剂。当前的2D心肌T1ρ映射需要多次屏气，并且覆盖范围有限。通过横diaphragm膜导航的呼吸门控最近已被用来实现自由呼吸的3DT1ρ映射，但是，其采集效率低，并且可能导致不可预测的长扫描时间。这项研究旨在开发一种具有高空间分辨率和可预测扫描时间的快速呼吸运动补偿3D全心心肌T1ρ定位技术。方法拟议的心电图（ECG）触发的T1ρ映射序列是在自由呼吸条件下使用螺旋状阶数的欠采样可变密度3D笛卡尔采样进行的。使用具有不同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一个饱和预脉冲，以在准备T1ρ之前重置磁化强度。图像导航器用于为每个T1ρ加权数据集启用心跳对心脏的2D平移呼吸运动校正，此后，执行3D平移配准以对齐所有T1ρ加权体积。使用基于多对比度3D补丁的低秩算法执行欠采样重建。与2DT1ρ作图相比，在11名健康受试者的体模和体内测试了所提出技术的准确性。在3名怀疑患有心血管疾病的患者中进一步研究了该技术的可行性。在患者中获取屏气后late增强（LGE）图像，作为疤痕检测的参考。结果Phantoms结果表明，与二维T1ρ映射参考相比，所提出的技术在广泛的模拟心率范围内提供了准确的T1ρ值。获得健康受试者的同质3DT1ρ图，间隔T1ρ为58.0±4.1 ms，与2D屏气测量结果相当（57.6±4.7 ms，P = 0.83）。3例患者中有1例检测到心肌疤痕，并且在梗塞区域观察到T1ρ值升高（87.4±5.7 ms）。结论在临床可行的约6分钟扫描时间内，开发了具有高呼吸扫描效率和接近各向同性的空间分辨率（1.7×1.7×2 mm3）的加速自由呼吸3D全心T1ρ映射技术。