背景:T1,T2和T1ρ是定量心脏MRI公认的参数。这些参数的同时估计允许全面的心肌组织表征,如心肌纤维化和水肿。然而,传统技术要么通过单独的屏气采集单独量化参数,这可能会导致未注册的参数映射,或估计长时间屏气采集中的多个参数,这可能是病人无法忍受的。我们提出了一种自由呼吸多参数映射(FB-MultiMap)技术,该技术可在一次有效采集中提供共同配准的心肌T1,T2和T1ρ图。
方法:所提出的FB-MultiMap在16个连续心动周期内执行心电图触发的单次笛卡尔采集,在那里反转,引入T2和T1ρ制剂以进行不同的对比。使用隔膜导航仪进行前瞻性的平面运动校正,并通过分组图像配准方法对平面运动进行回顾性校正。通过对运动校正图像的字典匹配进行定量映射,其中特定于主题的字典是使用Bloch模拟为一系列T1、T2和T1ρ值创建的,以及B1因素来解释B1的不均匀性。在数值仿真中对FB-MultiMap进行了优化和验证,幻影实验,15名健康受试者和6名疑似心脏病患者的体内成像。
结果:用FB-MultiMap估计的体模T1、T2和T1ρ值与参考测量值非常吻合,不依赖于心率。在健康的受试者中,FB-MultiMapT1高于MOLLIT1映射(1218±50msvs.1166±38ms,p<0.001)。与T2或T1ρ准备的2D平衡稳态自由进动的映射相比,用FB-MultiMap估计的心肌T2和T1ρ较低(T2:41.2±2.8msvs.42.5±3.1ms,p=0.06;T1ρ:45.3±4.4msvs.50.2±4.0,p<0.001)。在所有患者中,用FB-MultiMap测量的心肌参数的病理变化与常规技术一致。
结论:提出的自由呼吸多参数标测技术在16次心跳中提供了共同配准的心肌T1,T2和T1ρ图,实现与常规屏气映射方法相似的映射质量。
T1, T2 and T1ρ are well-recognized parameters for quantitative cardiac MRI. Simultaneous estimation of these parameters allows for comprehensive myocardial tissue characterization, such as myocardial fibrosis and edema. However, conventional techniques either quantify the parameters individually with separate breath-hold acquisitions, which may result in unregistered parameter maps, or estimate multiple parameters in a prolonged breath-hold acquisition, which may be intolerable to patients. We propose a free-breathing multi-parametric mapping (FB-MultiMap) technique that provides co-registered myocardial T1, T2 and T1ρ maps in a single efficient acquisition.
The proposed FB-MultiMap performs electrocardiogram-triggered single-shot Cartesian acquisition over 16 consecutive cardiac cycles, where inversion, T2 and T1ρ preparations are introduced for varying contrasts. A diaphragmatic navigator was used for prospective through-plane motion correction and the in-plane motion was corrected retrospectively with a group-wise image registration method. Quantitative mapping was conducted through dictionary matching of the motion corrected images, where the subject-specific dictionary was created using Bloch simulations for a range of T1, T2 and T1ρ values, as well as B1 factors to account for B1 inhomogeneities. The FB-MultiMap was optimized and validated in numerical simulations, phantom experiments, and in vivo imaging of 15 healthy subjects and six patients with suspected cardiac diseases.
The phantom T1, T2 and T1ρ values estimated with FB-MultiMap agreed well with reference measurements with no dependency on heart rate. In healthy subjects, FB-MultiMap T1 was higher than MOLLI T1 mapping (1218 ± 50 ms vs. 1166 ± 38 ms, p < 0.001). The myocardial T2 and T1ρ estimated with FB-MultiMap were lower compared to the mapping with T2- or T1ρ-prepared 2D balanced steady-state free precession (T2: 41.2 ± 2.8 ms vs. 42.5 ± 3.1 ms, p = 0.06; T1ρ: 45.3 ± 4.4 ms vs. 50.2 ± 4.0, p < 0.001). The pathological changes in myocardial parameters measured with FB-MultiMap were consistent with conventional techniques in all patients.
The proposed free-breathing multi-parametric mapping technique provides co-registered myocardial T1, T2 and T1ρ maps in 16 heartbeats, achieving similar mapping quality to conventional breath-hold mapping methods.