Deng Yufeng, Palmeri Mark L, Rouze Ned C, Haystead Clare M, Nightingale Kathryn R
Department of Biomedical Engineering, Duke University, Durham, North Carolina.
Department of Biomedical Engineering, Duke University, Durham, North Carolina.
Ultrasound Med Biol. 2018 Feb;44(2):303-310. doi: 10.1016/j.ultrasmedbio.2017.10.003. Epub 2017 Nov 21.
Harmonic imaging techniques have been applied in ultrasonic elasticity imaging to obtain higher-quality tissue motion tracking data. However, harmonic tracking can be signal-to-noise ratio and penetration depth limited during clinical imaging, resulting in decreased yield of successful shear wave speed measurements. A logical approach is to increase the source pressure, but the in situ pressures used in diagnostic ultrasound have been subject to a de facto upper limit based on the Food and Drug Administration guideline for the mechanical index (MI <1.9). A recent American Institute of Ultrasound in Medicine report concluded that an in situ MI up to 4.0 could be warranted without concern for increased risk of cavitation in non-fetal tissues without gas bodies if there were a concurrent clinical benefit. This work evaluates the impact of using an elevated MI in harmonic motion tracking for hepatic shear wave elasticity imaging. The studies indicate that high-MI harmonic tracking increased shear wave speed estimation yield by 27% at a focal depth of 5 cm, with larger yield increase in more difficult-to-image patients. High-MI tracking improved harmonic tracking data quality by increasing the signal-to-noise ratio and decreasing jitter in the tissue motion data. We conclude that there is clinical benefit to use of elevated acoustic output in shear wave tracking, particularly in difficult-to-image patients.
谐波成像技术已应用于超声弹性成像，以获取更高质量的组织运动跟踪数据。然而，在临床成像过程中，谐波跟踪可能受到信噪比和穿透深度的限制，导致成功测量剪切波速度的成功率降低。一种合理的方法是提高源压力，但根据美国食品药品监督管理局关于机械指数的指南（MI<1.9），诊断超声中使用的原位压力实际上存在上限。美国医学超声学会最近的一份报告得出结论，如果有同时存在的临床益处，对于没有气体的非胎儿组织，原位MI高达4.0是合理的，而无需担心空化风险增加。这项工作评估了在肝脏剪切波弹性成像的谐波运动跟踪中使用升高的MI的影响。研究表明，在5厘米的焦深处，高MI谐波跟踪使剪切波速度估计成功率提高了27%，在更难成像的患者中成功率提高幅度更大。高MI跟踪通过提高信噪比和减少组织运动数据中的抖动，改善了谐波跟踪数据质量。我们得出结论，在剪切波跟踪中使用升高的声输出具有临床益处，特别是在难成像的患者中。
