Department of Electrical and Computer Engineering, Hajim School of Engineering and Applied Sciences, University of Rochester, NY, USA.
IEEE Trans Ultrason Ferroelectr Freq Control. 2013 Feb;60(2):332-42. doi: 10.1109/TUFFC.2013.2569.
Stroke may occur when an atherosclerotic plaque ruptures in the carotid artery. Noninvasive vascular elastography (NIVE) visualizes the strain distribution within the carotid artery, which is related to its mechanical properties that govern plaque rupture. Strain elastograms obtained from the transverse plane of the carotid artery are difficult to interpret, because strain is estimated in Cartesian coordinates. Sparsearray (SA) elastography overcomes this problem by transforming shear and normal strain to polar coordinates. However, the SA's transmit power may be too weak to produce useful elastograms in the clinical setting. Consequently, we are exploring other imaging methods to solve this potential problem. This study evaluated the quality of elastograms produced with SA imaging, plane-wave (PW) imaging, and compounded-plane-wave (CPW) imaging. We performed studies on simulated and physical vessel phantoms, and the carotid artery of a healthy volunteer. All echo imaging was performed with a linear transducer array that contained 128 elements, operating at 5 MHz. In SA imaging, 7 elements were fired during transmission, but all 128 elements were active during reception. In PW imaging, all 128 elements were active during both transmission and reception. We created CPW images by steering the acoustic beam within the range of -15° to 15° in increments of 5°. SA radial and circumferential strain elastograms were comparable to those produced using PW and CPW imaging. Additionally, side-lobe levels incurred during SA imaging were 20 dB lower than those produced during PW imaging, and 10 dB lower than those computed using CPW imaging. Overall, SA imaging performs well in vivo; therefore, we plan to improve the technique and perform preclinical studies.
当颈动脉中的动脉粥样硬化斑块破裂时，可能会发生中风。无创血管弹成像（NIVE）可视化颈动脉内的应变分布，这与控制斑块破裂的机械特性有关。从颈动脉的横切面获得的应变弹性图难以解释，因为应变是在笛卡尔坐标系中估计的。稀疏数组（SA）弹性成像通过将剪切和法向应变转换为极坐标来克服这个问题。然而，SA 的发射功率可能太弱，无法在临床环境中产生有用的弹性图。因此，我们正在探索其他成像方法来解决这个潜在的问题。本研究评估了使用 SA 成像、平面波（PW）成像和复合平面波（CPW）成像产生的弹性图的质量。我们在模拟和物理血管模型以及健康志愿者的颈动脉上进行了研究。所有回声成像都是使用包含 128 个元件的线性换能器阵列在 5 MHz 下进行的。在 SA 成像中，在发射期间发射 7 个元件，但在接收期间所有 128 个元件都是活动的。在 PW 成像中，在发射和接收期间，所有 128 个元件都是活动的。我们通过在 -15°至 15°的范围内以 5°的增量引导声束来创建 CPW 图像。SA 径向和周向应变弹性图与使用 PW 和 CPW 成像产生的弹性图相当。此外，在 SA 成像过程中产生的旁瓣电平比在 PW 成像过程中产生的低 20 dB，比使用 CPW 成像计算的低 10 dB。总体而言，SA 成像在体内表现良好；因此，我们计划改进该技术并进行临床前研究。
