Kusunose Jiro, Caskey Charles F
Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, Tennessee, USA.
Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, Tennessee, USA; Department of Radiology and Radiologic Sciences, Vanderbilt University Medical Center, Nashville, Tennessee, USA; Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA.
Ultrasound Med Biol. 2018 Oct;44(10):2131-2142. doi: 10.1016/j.ultrasmedbio.2018.05.020. Epub 2018 Jul 26.
Plane-wave ultrasound contrast imaging offers a faster, less destructive means for imaging microbubbles compared with traditional ultrasound imaging. Even though many of the most acoustically responsive microbubbles have resonant frequencies in the lower-megahertz range, higher frequencies (>3 MHz) have typically been employed to achieve high spatial resolution. In this work we implement and optimize low-frequency (1.5-4 MHz) plane-wave pulse inversion imaging on a commercial, phased-array imaging transducer in vitro and illustrate its use in vivo by imaging a mouse xenograft model. We found that the 1.8-MHz contrast signal was about four times that acquired at 3.1 MHz on matched probes and nine times greater than echoes received on a higher-frequency probe. Low-frequency imaging was also much more resilient to motion. In vivo, we could identify sub-millimeter vasculature inside a xenograft tumor model and easily assess microbubble half-life. Our results indicate that low-frequency imaging can provide better signal-to-noise because it generates stronger non-linear responses. Combined with high-speed plane-wave imaging, this method could open the door to super-resolution imaging at depth, while high power pulses could be used for image-guided therapeutics.
与传统超声成像相比，平面波超声造影成像为微泡成像提供了一种更快、破坏性更小的方法。尽管许多声学响应最强的微泡的共振频率在较低的兆赫兹范围内，但通常采用较高频率（>3兆赫兹）来实现高空间分辨率。在这项工作中，我们在商用相控阵成像换能器上实施并优化了低频（1.5 - 4兆赫兹）平面波脉冲反转成像，并通过对小鼠异种移植模型成像来说明其在体内的应用。我们发现，在匹配的探头中，1.8兆赫兹的造影信号约为3.1兆赫兹时所采集信号的四倍，比在高频探头上接收到的回波大九倍。低频成像对运动的耐受性也更强。在体内，我们能够识别异种移植肿瘤模型内的亚毫米级脉管系统，并轻松评估微泡的半衰期。我们的结果表明，低频成像可以提供更好的信噪比，因为它能产生更强的非线性响应。结合高速平面波成像，这种方法可以为深度超分辨率成像打开大门，而高功率脉冲可用于图像引导治疗。
