Jahnke Cosima, Nehrke Kay, Paetsch Ingo, Schnackenburg Bernhard, Gebker Rolf, Fleck Eckart, Nagel Eike
Department of Internal Medicine/Cardiology, German Heart Institute Berlin, Berlin, Germany.
J Magn Reson Imaging. 2007 Sep;26(3):780-6. doi: 10.1002/jmri.21078.
To evaluate the impact of a new, cross-correlation based method for compensation of respiratory induced motion of the heart using an individually adapted three-dimensional (3D) translation or affine transformation approach.
A total of 32 patients underwent a routine cardiac MR examination. In each patient, a calibration scan was performed during free-breathing to register breathing-related motion within a 3D ellipsoid registration kernel covering the entire heart. Three navigators were employed for all three spatial dimensions (feet-head, anterior-posterior, and left-right) and the optimal translatory correction factors for each spatial dimension were determined. In addition, the cross-correlations for different motion models (no compensation, fixed 1D-translation, adapted 3D-translation, and affine transformation) were calculated.
The mean correction factor for the feet-head direction was 0.45 +/- 0.13. Though the mean correction factors for the anterior-posterior and left-right direction were nearly zero (-0.01 +/- 0.08 and 0.02 +/- 0.09, respectively), the correction factors exceeded the amount of 0.1 in 12 (19%) and in 19 patients (30%), respectively. All motion compensation models showed significantly higher cross-correlations when compared to "no compensation" (P < 0.05). In particular, the affine transformation algorithm achieved the highest cross-correlation values (88.3 +/- 5.1%) with a significant increase compared to fixed 1D translation (84.7 +/- 6.5%, P < 0.05).
A considerable number of patients demonstrated relevant breathing-related movement of the heart in the anterior-posterior or left-right direction in addition to the predominant breathing-related movement in the feet-head direction. Thus, it is recommended to compensate for all three spatial dimensions. The affine transformation algorithm combined with three navigators significantly improved breathing-related cardiac motion compensation when compared to the conventionally applied 1D translation with a fixed correction factor.
使用个体适配的三维（3D）平移或仿射变换方法，评估一种基于互相关的新方法对心脏呼吸诱导运动的补偿效果。
共有32例患者接受了常规心脏磁共振检查。对每位患者在自由呼吸状态下进行一次校准扫描，以在覆盖整个心脏的3D椭球配准内核内记录与呼吸相关的运动。在所有三个空间维度（头足、前后、左右）均采用三个导航器，并确定每个空间维度的最佳平移校正因子。此外，计算了不同运动模型（无补偿、固定一维平移、适配3D平移和仿射变换）的互相关。
头足方向的平均校正因子为0.45±0.13。虽然前后方向和左右方向的平均校正因子几乎为零（分别为-0.01±0.08和0.02±0.09），但校正因子分别在12例（19%）和19例（30%）患者中超过了0.1。与“无补偿”相比，所有运动补偿模型的互相关均显著更高（P<0.05）。特别是，仿射变换算法获得了最高的互相关值（88.3±5.1%），与固定一维平移（84.7±6.5%，P<0.05）相比有显著提高。
相当数量的患者除了在头足方向存在主要的与呼吸相关的运动外，在前后或左右方向也表现出与呼吸相关的心脏运动。因此，建议对所有三个空间维度进行补偿。与传统应用的固定校正因子的一维平移相比，仿射变换算法结合三个导航器显著改善了与呼吸相关的心脏运动补偿。
