应用 subtly-tagged 稳态自由进动特征追踪技术评估左心室功能和局部应变。

Left ventricular function and regional strain with subtly-tagged steady-state free precession feature tracking.

机构信息

Translational Medicine, the Hospital for Sick Children, Toronto, Canada.

Department of Anatomy with Radiology, University of Auckland, Auckland, New Zealand.

出版信息

J Magn Reson Imaging. 2018 Mar;47(3):787-797. doi: 10.1002/jmri.25819. Epub 2017 Jul 19.

DOI:10.1002/jmri.25819

PMID:28722247

Abstract

PURPOSE

To provide regional strain and ventricular volume from a single acquisition, using subtly tagged steady-state free precession (SubTag SSFP) feature tracking.

MATERIALS AND METHODS

The effects on regional strain of tag strength in gradient recalled echo (GRE) tagging, flip angle in untagged balanced SSFP, and both in SubTag SSFP were examined in the mid left ventricle of 15 healthy volunteers at 3T. Optimal parameters were determined from varying both tag strength and SSFP flip angle using full tag saturation GRE as the reference standard. SubTag SSFP was acquired in 15 additional healthy volunteers for whole-heart volume and strain assessment using the optimized parameters. Values measured by two image analysts were compared to clinical reference standards from untagged SSFP (volumes) and GRE tagging (strains).

RESULTS

Regional strain accuracy was maintained with decreasing total tagging flip angle (β); less than 3% differences for β ≥ 26°. For untagged SSFP flip angle (α), whole-wall strain differences became statistically significant when α < 40°. A SubTag SSFP acquisition with α = 40° and β = 46° showed the best combination of tagging strength, blood-myocardial contrast, and tag persistence at end-systole for regional strain estimation. SubTag SSFP also showed excellent agreement with untagged SSFP for volumetrics (percent difference: end-diastolic volume = 0.6%, end-systolic volume = 0.4%, stroke volume = 1.2%, ejection fraction = 0.6%, mass = 1.1%).

CONCLUSION

Feature tracking for regional myocardial strain assessment is dependent on image features, mainly the tag strength, persistence, and image contrast. SubTag SSFP balances these criteria to provide accurate regional strain and volumetric assessment in a single acquisition.

LEVEL OF EVIDENCE

1 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2018;47:787-797.

摘要

目的

利用 subtlytagged 稳态自由进动（SubTag SSFP）特征追踪技术，从单次采集获得区域性应变和心室容积。

材料与方法

在 3T 下，对 15 名健康志愿者的左心室中部进行梯度回波（GRE）标记中的标记强度、未标记平衡稳态自由进动（SSFP）中的翻转角以及 SubTag SSFP 中这两者对区域性应变的影响进行了检查。使用全标记饱和 GRE 作为参考标准，通过改变标记强度和 SSFP 翻转角来确定最佳参数。使用优化后的参数，在另外 15 名健康志愿者中采集 SubTag SSFP，用于全心室容积和应变评估。由两名图像分析员测量的值与来自未标记 SSFP（容积）和 GRE 标记（应变）的临床参考标准进行了比较。

结果

随着总标记翻转角（β）的降低，区域性应变的准确性得以保持；当β≥26°时，差异小于 3%。对于未标记 SSFP 的翻转角（α），当α<40°时，全壁应变差异具有统计学意义。在进行区域性应变估计时，采用α=40°、β=46°的 SubTag SSFP 采集可获得最佳的标记强度、血心肌对比度和标记在收缩末期的持久性组合。SubTag SSFP 与未标记 SSFP 相比，在容积学方面也具有极好的一致性（百分比差异：舒张末期容积=0.6%，收缩末期容积=0.4%，搏出量=1.2%，射血分数=0.6%，质量=1.1%）。