Kuijer J P, Jansen E, Marcus J T, van Rossum A C, Heethaar R M
Dept. of Clinical Physics & Informatics, Vrije Universiteit Medical Center, Amsterdam, The Netherlands.
Magn Reson Med. 2001 Nov;46(5):993-9. doi: 10.1002/mrm.1286.
Magnetic resonance tagging has proven a valuable tool in the quantification of myocardial deformation. However, time-consuming postprocessing has discouraged the use of this technique in clinical routine. Recently, the harmonic phase (HARP) technique was introduced for automatic calculation of myocardial strain maps from tagged images. In this study, a comparison was made between HARP instantaneous strain maps calculated from single tagged images (SPAMM) and those calculated from subtracted tagged images (CSPAMM). The performance was quantified using simulated images of an incompressible cylinder in the 'end-systolic' state with realistic image contrast and noise. The error in the second principal stretch ratio was 0.009 +/- 0.032 (mean +/- SD) for the SPAMM acquisition, and 0.007 +/- 0.016 for CSPAMM at identical contrast-to-noise ratio. Furthermore, differences between the methods were illustrated with in vivo strain maps. Those calculated from CSPAMM images showed fewer artifacts and were less sensitive to the choice of cut-off frequencies in the HARP band-pass filter. A prerequisite for the method to become practical is that the CSPAMM images should be acquired in a single breathhold.
磁共振标记已被证明是定量心肌变形的一种有价值的工具。然而，耗时的后处理阻碍了该技术在临床常规中的应用。最近，谐波相位（HARP）技术被引入用于从标记图像自动计算心肌应变图。在本研究中，对从单标记图像（SPAMM）计算得到的HARP瞬时应变图与从相减标记图像（CSPAMM）计算得到的应变图进行了比较。使用具有逼真图像对比度和噪声的“收缩末期”状态下不可压缩圆柱体的模拟图像对性能进行了量化。在相同的对比度噪声比下，SPAMM采集的第二主拉伸比误差为0.009±0.032（平均值±标准差），CSPAMM为0.007±0.016。此外，用体内应变图说明了方法之间的差异。从CSPAMM图像计算得到的应变图伪影较少，并且对HARP带通滤波器截止频率的选择不太敏感。该方法实用的一个前提是CSPAMM图像应在一次屏气中采集。
