Roujol Sébastien, Foppa Murilo, Weingärtner Sebastian, Manning Warren J, Nezafat Reza
Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA.
Magn Reson Med. 2015 Apr;73(4):1469-82. doi: 10.1002/mrm.25270. Epub 2014 May 5.
To propose and evaluate a novel nonrigid image registration approach for improved myocardial T1 mapping.
Myocardial motion is estimated as global affine motion refined by a novel local nonrigid motion estimation algorithm. A variational framework is proposed, which simultaneously estimates motion field and intensity variations, and uses an additional regularization term to constrain the deformation field using automatic feature tracking. The method was evaluated in 29 patients by measuring the DICE similarity coefficient and the myocardial boundary error in short axis and four chamber data. Each image series was visually assessed as "no motion" or "with motion." Overall T1 map quality and motion artifacts were assessed in the 85 T1 maps acquired in short axis view using a 4-point scale (1-nondiagnostic/severe motion artifact, 4-excellent/no motion artifact).
Increased DICE similarity coefficient (0.78 ± 0.14 to 0.87 ± 0.03, P < 0.001), reduced myocardial boundary error (1.29 ± 0.72 mm to 0.84 ± 0.20 mm, P < 0.001), improved overall T1 map quality (2.86 ± 1.04 to 3.49 ± 0.77, P < 0.001), and reduced T1 map motion artifacts (2.51 ± 0.84 to 3.61 ± 0.64, P < 0.001) were obtained after motion correction of "with motion" data (∼56% of data).
The proposed nonrigid registration approach reduces the respiratory-induced motion that occurs during breath-hold T1 mapping, and significantly improves T1 map quality.
提出并评估一种用于改进心肌T1映射的新型非刚性图像配准方法。
心肌运动被估计为通过一种新型局部非刚性运动估计算法细化的全局仿射运动。提出了一个变分框架，该框架同时估计运动场和强度变化，并使用一个额外的正则化项通过自动特征跟踪来约束变形场。通过测量短轴和四腔数据中的DICE相似系数和心肌边界误差，在29名患者中对该方法进行了评估。每个图像序列在视觉上被评估为“无运动”或“有运动”。使用4分制（1-非诊断性/严重运动伪影，4-优秀/无运动伪影）对短轴视图中获取的85幅T1映射图的整体T1映射图质量和运动伪影进行评估。
在对“有运动”数据（约占数据的56%）进行运动校正后，DICE相似系数增加（从0.78±0.14提高到0.87±0.03，P<0.001）、心肌边界误差减小（从1.29±0.72毫米减小到0.84±0.20毫米，P<0.001）、整体T1映射图质量提高（从2.86±1.04提高到3.49±0.77，P<0.001）以及T1映射图运动伪影减少（从2.51±0.84减小到3.61±0.64，P<0.001）。
所提出的非刚性配准方法减少了屏气T1映射过程中发生的呼吸诱导运动，并显著提高了T1映射图质量。
