MR Applications & Workflow, GE Healthcare, Barcelona, Spain.
Universitat de Barcelona, Barcelona, Spain.
Sci Rep. 2021 Sep 17;11(1):18546. doi: 10.1038/s41598-021-97841-z.
Myocardial tissue T1 constitutes a reliable indicator of several heart diseases related to extracellular changes (e.g. edema, fibrosis) as well as fat, iron and amyloid content. Magnetic resonance (MR) T1-mapping is typically achieved by pixel-wise exponential fitting of a series of inversion or saturation recovery measurements. Good anatomical alignment between these measurements is essential for accurate T1 estimation. Motion correction is recommended to improve alignment. However, in the case of inversion recovery sequences, this correction is compromised by the intrinsic contrast variation between frames. A model-based, non-rigid motion correction method for MOLLI series was implemented and validated on a large database of cardiac clinical cases (n = 186). The method relies on a dedicated similarity metric that accounts for the intensity changes caused by T1 magnetization relaxation. The results were compared to uncorrected series and to the standard motion correction included in the scanner. To automate the quantitative analysis of results, a custom data alignment metric was defined. Qualitative evaluation was performed on a subset of cases to confirm the validity of the new metric. Motion correction caused noticeable (i.e. > 5%) performance degradation in 12% of cases with the standard method, compared to 0.3% with the new dedicated method. The average alignment quality was 85% ± 9% with the default correction and 90% ± 7% with the new method. The results of the qualitative evaluation were found to correlate with the quantitative metric. In conclusion, a dedicated motion correction method for T1 mapping MOLLI series has been evaluated on a large database of clinical cardiac MR cases, confirming its increased robustness with respect to the standard method implemented in the scanner.
心肌组织 T1 是多种与细胞外变化（如水肿、纤维化）以及脂肪、铁和淀粉样蛋白含量相关的心脏疾病的可靠指标。磁共振（MR）T1 映射通常通过对一系列反转或饱和恢复测量进行逐像素指数拟合来实现。这些测量之间良好的解剖配准对于准确的 T1 估计至关重要。建议进行运动校正以改善配准。然而，在反转恢复序列的情况下，这种校正会因帧之间的固有对比度变化而受到影响。针对 MOLLI 序列实现了一种基于模型的非刚性运动校正方法，并在大量心脏临床病例数据库（n=186）上进行了验证。该方法依赖于专门的相似度度量，该度量考虑了 T1 磁化弛豫引起的强度变化。结果与未校正系列和扫描仪中包含的标准运动校正进行了比较。为了自动分析结果，定义了自定义数据对齐度量。在一部分病例中进行了定性评估，以确认新度量的有效性。与标准方法相比，在 12%的病例中，标准方法会导致明显（即>5%）的性能下降，而新的专用方法仅为 0.3%。默认校正的平均对齐质量为 85%±9%，新方法为 90%±7%。定性评估的结果与定量度量相关。总之，已经在大量临床心脏 MR 病例数据库上评估了用于 T1 映射 MOLLI 序列的专用运动校正方法，证实了与扫描仪中实现的标准方法相比，该方法具有更高的稳健性。
