基于特征追踪和 DENSE CMR 的左心室应变和扭转的比较。
Comparison of left ventricular strains and torsion derived from feature tracking and DENSE CMR.
机构信息
Department of Biomedical Engineering, University of Kentucky, Lexington, KY, USA.
Department of Imaging Science and Innovation, Geisinger, 100 North Academy Avenue, Danville, PA, 17822-4400, USA.
出版信息
J Cardiovasc Magn Reson. 2018 Sep 13;20(1):63. doi: 10.1186/s12968-018-0485-4.
BACKGROUND
Cardiovascular magnetic resonance (CMR) feature tracking is increasingly used to quantify cardiac mechanics from cine CMR imaging, although validation against reference standard techniques has been limited. Furthermore, studies have suggested that commonly-derived metrics, such as peak global strain (reported in 63% of feature tracking studies), can be quantified using contours from just two frames - end-diastole (ED) and end-systole (ES) - without requiring tracking software. We hypothesized that mechanics derived from feature tracking would not agree with those derived from a reference standard (displacement-encoding with stimulated echoes (DENSE) imaging), and that peak strain from feature tracking would agree with that derived using simple processing of only ED and ES contours.
METHODS
We retrospectively identified 88 participants with 186 pairs of DENSE and balanced steady state free precession (bSSFP) image slices acquired at the same locations across two institutions. Left ventricular (LV) strains, torsion, and dyssynchrony were quantified from both feature tracking (TomTec Imaging Systems, Circle Cardiovascular Imaging) and DENSE. Contour-based strains from bSSFP images were derived from ED and ES contours. Agreement was assessed with Bland-Altman analyses and coefficients of variation (CoV). All biases are reported in absolute percentage.
RESULTS
Comparison results were similar for both vendor packages (TomTec and Circle), and thus only TomTec Imaging System data are reported in the abstract for simplicity. Compared to DENSE, mid-ventricular circumferential strain (Ecc) from feature tracking had acceptable agreement (bias: - 0.4%, p = 0.36, CoV: 11%). However, feature tracking significantly overestimated the magnitude of Ecc at the base (bias: - 4.0% absolute, p < 0.001, CoV: 18%) and apex (bias: - 2.4% absolute, p = 0.01, CoV: 15%), underestimated torsion (bias: - 1.4 deg/cm, p < 0.001, CoV: 41%), and overestimated dyssynchrony (bias: 26 ms, p < 0.001, CoV: 76%). Longitudinal strain (Ell) had borderline-acceptable agreement (bias: - 0.2%, p = 0.77, CoV: 19%). Contour-based strains had excellent agreement with feature tracking (biases: - 1.3-0.2%, CoVs: 3-7%).
CONCLUSION
Compared to DENSE as a reference standard, feature tracking was inaccurate for quantification of apical and basal LV circumferential strains, longitudinal strain, torsion, and dyssynchrony. Feature tracking was only accurate for quantification of mid LV circumferential strain. Moreover, feature tracking is unnecessary for quantification of whole-slice strains (e.g. base, apex), since simplified processing of only ED and ES contours yields very similar results to those derived from feature tracking. Current feature tracking technology therefore has limited utility for quantification of cardiac mechanics.
背景
心血管磁共振（CMR）特征追踪技术越来越多地用于从电影 CMR 成像中定量心脏力学，尽管与参考标准技术的验证有限。此外，研究表明，通常衍生的指标，如峰值整体应变（在 63%的特征追踪研究中报告），可以仅使用两个帧的轮廓来定量-舒张末期（ED）和收缩末期（ES）-而无需跟踪软件。我们假设特征追踪得出的力学与参考标准（位移编码刺激回波（DENSE）成像）得出的力学不一致，并且特征追踪得出的峰值应变与仅使用 ED 和 ES 轮廓的简单处理得出的应变一致。
方法
我们回顾性地在两个机构中识别出了 88 名参与者，他们具有 186 对 DENSE 和平衡稳态自由进动（bSSFP）图像切片。从特征追踪（TomTec Imaging Systems，Circle Cardiovascular Imaging）和 DENSE 定量左心室（LV）应变、扭转和不同步性。从 bSSFP 图像的基于轮廓的应变来自 ED 和 ES 轮廓。使用 Bland-Altman 分析和变异系数（CoV）评估一致性。所有偏差均以绝对值报告。
结果
两种供应商软件包（TomTec 和 Circle）的比较结果相似，因此为简单起见，仅在摘要中报告 TomTec Imaging System 数据。与 DENSE 相比，特征追踪的中隔室圆周应变（Ecc）具有可接受的一致性（偏差：-0.4%，p=0.36，CoV：11%）。然而，特征追踪显着高估了基底（偏差：-4.0%绝对值，p<0.001，CoV：18%）和顶点（偏差：-2.4%绝对值，p=0.01，CoV：15%）处 Ecc 的幅度，低估了扭转（偏差：-1.4 度/厘米，p<0.001，CoV：41%），并高估了不同步性（偏差：26 毫秒，p<0.001，CoV：76%）。纵向应变（Ell）具有边缘可接受的一致性（偏差：-0.2%，p=0.77，CoV：19%）。基于轮廓的应变与特征追踪具有极好的一致性（偏差：-1.3-0.2%，CoV：3-7%）。
结论
与 DENSE 作为参考标准相比，特征追踪对于定量 LV 心尖和基底圆周应变、纵向应变、扭转和不同步性的准确性较差。特征追踪仅适用于定量中隔室圆周应变。此外，由于仅对 ED 和 ES 轮廓进行简单处理即可产生与特征追踪非常相似的结果，因此特征追踪对于定量整个切片应变（例如基底、顶点）是不必要的。因此，当前的特征追踪技术对于心脏力学的定量具有有限的实用性。
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