a School of Microelectronics , Tianjin University , Tianjin , China.
b Graduate Institute of Clinical Medical Sciences, College of Medicine, Chang Gung University , Taoyuan , Taiwan.
Int J Hyperthermia. 2018;35(1):548-558. doi: 10.1080/02656736.2018.1512160. Epub 2018 Oct 25.
Radiofrequency (RF) ablation (RFA) is the most commonly used minimally invasive procedure for thermal ablation of liver tumors. Ultrasound not only provides real-time feedback of the electrode location for RFA guidance but also enables visualization of the tissue temperature. Changes in backscattered energy (CBE) have been widely applied to ultrasound temperature imaging for assessing thermal ablation. Pilot studies have revealed that significant shadowing features appear in CBE imaging and are caused by the electrode and RFA-induced gas bubbles. To resolve this problem, the current study proposed ultrasound single-phase CBE imaging based on positive CBE values. An in vitro model with tissue samples derived from the porcine tenderloin was used to validate the proposed method. During RFA with various electrode lengths, ultrasound scans of tissue samples were obtained using a clinical ultrasound scanner equipped with a convex array transducer of 3 MHz. Raw image data comprising 256 scan lines of backscattered RF signals were acquired for B-mode, conventional CBE, and single-phase CBE imaging by using the proposed algorithmic scheme. The ablation sizes estimated using CBE imaging and gross examinations were compared to calculate the correlation coefficient. The experimental results indicated that single-phase CBE imaging largely suppressed artificial CBE information in the shadowed region. Moreover, compared with conventional CBE imaging, single-phase CBE imaging provided a more accurate estimation of ablation sizes (the correlation coefficient was higher than 0.8).
射频（RF）消融（RFA）是用于肝脏肿瘤热消融的最常用的微创程序。超声不仅为 RFA 引导提供电极位置的实时反馈，还能够可视化组织温度。背散射能量（CBE）的变化已广泛应用于超声温度成像以评估热消融。初步研究表明，在 CBE 成像中出现明显的阴影特征，这是由电极和 RFA 诱导的气泡引起的。为了解决这个问题，本研究提出了基于正 CBE 值的超声单相 CBE 成像。使用源自猪里脊肉的组织样本的体外模型来验证所提出的方法。在具有各种电极长度的 RFA 期间，使用配备 3MHz 凸阵换能器的临床超声扫描仪对组织样本进行超声扫描。通过使用所提出的算法方案，从回波射频信号的 256 条扫描线中获取用于 B 模式、常规 CBE 和单相 CBE 成像的原始图像数据。使用 CBE 成像和大体检查估计的消融大小来计算相关系数。实验结果表明，单相 CBE 成像在很大程度上抑制了阴影区域中的人为 CBE 信息。此外，与常规 CBE 成像相比，单相 CBE 成像提供了更准确的消融尺寸估计（相关系数高于 0.8）。
