University of Chicago Medical Center, Chicago, Illinois, USA.
J Am Soc Echocardiogr. 2012 Sep;25(9):978-85. doi: 10.1016/j.echo.2012.06.001. Epub 2012 Jul 4.
Myocardial strain is useful in the evaluation of left ventricular function using high-frame rate two-dimensional (2D) speckle-tracking echocardiography (STE). Three-dimensional (3D) STE allows 3D measurement of myocardial deformation, which is potentially more accurate, because it is not affected by through-plane motion. However, the low frame rates of 3D STE are a potential limitation that has not been studied to date. Whereas with 2D STE, high frame rates are necessary because speckles may move out of the imaging plane, it was hypothesized that because they always remain within the scan volume, they should be tracked with 3D STE, even if frame rates are considerably lower.
Twenty-seven subjects were studied, including 16 normal volunteers and 11 patients with nonischemic dilated cardiomyopathy, who underwent 2D (frame rate, 62 ± 9 frames/sec) and 3D echocardiographic imaging. In normal subjects, 3D imaging was performed at four different frame rates, achieved by varying the number of beats used for full-volume acquisition (six, four, two, and one). In the patients with dilated cardiomyopathy, 3D imaging was performed using a four-beat acquisition. The principal components of strain and the corresponding strain rates were calculated in 16 myocardial segments and averaged. Both 2D and 3D images were analyzed using TomTec software to avoid analysis-related differences.
In normal subjects, strain and strain rate values were the same for 3D STE with six-beat and four-beat full-volume data sets, corresponding to 25 and 18 frames/sec, respectively. In contrast, 3D STE with one-beat and two-beat data sets, corresponding to 5 and 10 frames/sec, respectively, resulted in significantly lower values. Strain and strain rate values derived from six-beat and four-beat 3D data sets were not significantly lower than 2D STE-derived values, indicating that there was no loss of information due to lower frame rates. In patients with dilated cardiomyopathy, both 2D STE-derived and 3D STE-derived strain values were significantly reduced compared with normal hearts. The differences between 2D STE-derived and 3D STE-derived strain values echoed those noted in the normal subjects.
Three-dimensional speckle-tracking echocardiographic assessment of myocardial deformation is not compromised by low frame rates when derived from 18 or 25 frames/sec data sets but is underestimated with lower frame rates.
心肌应变成像技术（STE）利用高帧率二维（2D）斑点追踪技术评估左心室功能。三维（3D）STE 允许对心肌变形进行 3D 测量，这可能更准确，因为它不受平面外运动的影响。然而，3D STE 的低帧率是一个尚未研究的潜在限制。虽然 2D STE 需要高帧率，因为斑点可能会移出成像平面，但假设由于它们始终在扫描体积内，因此即使帧率低得多，也应该用 3D STE 对其进行跟踪。
对 27 名受试者进行了研究，包括 16 名正常志愿者和 11 名非缺血性扩张型心肌病患者，他们接受了二维（帧率为 62±9 帧/秒）和三维超声心动图检查。在正常受试者中，通过改变用于全容积采集的心跳数（6、4、2 和 1），在四个不同的帧率下进行 3D 成像。在扩张型心肌病患者中，使用四拍采集进行 3D 成像。在 16 个心肌节段计算应变的主成分，并对其进行平均。使用 TomTec 软件分析 2D 和 3D 图像，以避免分析相关的差异。
在正常受试者中，六拍和四拍全容积数据集的 3D STE 的应变和应变速率值相同，分别对应 25 和 18 帧/秒。相比之下，一拍和两拍数据集的 3D STE，分别对应 5 和 10 帧/秒，结果明显较低。六拍和四拍 3D 数据集得出的应变和应变速率值并不明显低于 2D STE 得出的值，表明由于帧率较低而没有丢失信息。在扩张型心肌病患者中，二维应变与三维应变与正常心脏相比均显著降低。二维应变与三维应变值之间的差异与在正常受试者中观察到的差异一致。
当源自 18 或 25 帧/秒的数据时，3D STE 评估心肌变形不受低帧率的影响，但当帧率较低时，其结果会被低估。
