Bharat Shyam, Techavipoo Udomchai, Kiss Miklos Z, Liu Wu, Varghese Tomy
Department of Medical Physics, University of Wisconsin-Madison, Madison, WI 53706, USA.
Ultrasound Med Biol. 2005 Mar;31(3):415-22. doi: 10.1016/j.ultrasmedbio.2004.12.020.
The variations in the stiffness or stiffness contrast of lesions resulting from radiofrequency (RF) ablation of canine liver tissue at different temperatures and for different ablation durations at a specified temperature are analyzed. Tissue stiffness, in general, increases with temperature; however, an anomaly exists around 80 degrees C, where the stiffness of the lesion is lower than that of the lesion ablated at 70 degrees C. On the other hand, the stiffness increases monotonically with the duration of ablation. Plots illustrating the ratio of mean strains in normal canine liver tissue to mean strains in ablated thermal lesions demonstrate the variation in the stiffness contrast of the thermal lesions. The contrast-to-noise ratio (CNRe) of the lesions, which serves as an indicator of the detectability of the lesions under the different experimental imaging conditions described above, is also presented. The results presented in this paper show that the elastographic depiction of stiffer thermal lesions is better, in terms of the CNRe parameter. An important criterion in the elastographic depiction of RF-ablated regions of tissue is the trade-off between ablation temperature and duration of ablation. Tissue necrosis can occur either by ablating tissue to high temperatures for short durations or to lower temperatures for longer durations. In this paper, we attempt to characterize the elastographic depiction of thermal lesions under these different experimental conditions. This paper provides results that may be utilized by practitioners of RF ablation to decide the ablation temperature and duration, on the basis of the strain images of normal liver tissue and ablated thermal lesions discussed in this paper.
分析了在不同温度下以及在特定温度下不同消融持续时间对犬肝组织进行射频（RF）消融所导致的病变硬度或硬度对比度的变化。一般来说，组织硬度随温度升高而增加；然而，在80摄氏度左右存在异常情况，此时病变的硬度低于在70摄氏度下消融的病变。另一方面，硬度随消融持续时间单调增加。展示正常犬肝组织平均应变与消融热损伤平均应变之比的图表表明了热损伤硬度对比度的变化。还给出了病变的对比噪声比（CNRe），它作为上述不同实验成像条件下病变可检测性的指标。本文给出的结果表明，就CNRe参数而言，对较硬热损伤的弹性成像描绘更好。在组织射频消融区域的弹性成像描绘中，一个重要标准是消融温度与消融持续时间之间的权衡。组织坏死既可以通过短时间将组织消融至高温，也可以通过长时间将组织消融至较低温度来实现。在本文中，我们试图描述在这些不同实验条件下热损伤的弹性成像描绘。本文提供的结果可供射频消融从业者根据本文讨论的正常肝组织和消融热损伤的应变图像来决定消融温度和持续时间。
