Samimi Kayvan, White James K, Brace Christopher L, Varghese Tomy
Department of Electrical and Computer Engineering, College of Engineering, University of Wisconsin, Madison, Wisconsin, USA.
Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA.
Ultrasound Med Biol. 2017 Jul;43(7):1441-1451. doi: 10.1016/j.ultrasmedbio.2017.03.010. Epub 2017 Apr 26.
Thermal ablation of soft tissue changes the tissue microstructure and, consequently, induces changes in its acoustic properties. Although B-mode ultrasound provides high-resolution and high-frame-rate images of ablative therapeutic procedures, it is not particularly effective at delineating boundaries of ablated regions because of poor contrast in echogenicity between ablated and surrounding normal tissue. Quantitative ultrasound techniques can provide quantitative estimates of acoustic properties, such as backscatter and attenuation coefficients, and differentiate ablated and unablated regions more effectively, with the potential for monitoring minimally invasive thermal therapies. In this study, a previously introduced attenuation estimation method was used to create quantitative attenuation coefficient maps for 11 microwave ablation procedures performed on refrigerated ex vivo bovine liver. The attenuation images correlate well with the pathologic images of the ablated region. The mean attenuation coefficient for regions of interest drawn inside and outside the ablated zones were 0.9 (±0.2) and 0.45 (±0.15) dB/cm/MHz, respectively. These estimates agree with reported values in the literature and establish the usefulness of non-invasive attenuation imaging for monitoring therapeutic procedures in the liver.
软组织的热消融会改变组织微观结构，进而引起其声学特性的变化。尽管B超能够提供消融治疗过程的高分辨率和高帧率图像，但由于消融组织与周围正常组织的回声性对比度较差，它在描绘消融区域边界方面效果欠佳。定量超声技术可以提供声学特性的定量估计，如背向散射和衰减系数，并能更有效地区分消融和未消融区域，具有监测微创热疗法的潜力。在本研究中，一种先前引入的衰减估计方法被用于为11例在冷藏的离体牛肝上进行的微波消融手术创建定量衰减系数图。衰减图像与消融区域的病理图像相关性良好。在消融区内外绘制的感兴趣区域的平均衰减系数分别为0.9（±0.2）和0.45（±0.15）dB/cm/MHz。这些估计值与文献报道的值相符，并证实了无创衰减成像在监测肝脏治疗过程中的实用性。
