低机械指数灰阶造影对肝VX2瘤动态期相性变化的研究

Low mechanical index gray-scale contrast enhancement in rabbit liver VX2 tumor

目的应用低机械指数灰阶超声造影研究肝恶性肿瘤的动态期相性增强变化规律及其诊断价值。方法分别经耳缘静脉对8只荷VX2瘤新西兰大白兔团注超声造影剂SonoVue(0.1ml/kg),应用CnTI低机械指数实时造影匹配成像技术,动态观察兔VX2瘤及其周围肝实质造影增强效应。结果在所有造影过程中,肝肿瘤及肝实质内造影剂随时间呈动态增强。VX2瘤动脉期明显强化,呈“灯泡征”,与周围肝组织灰阶对比明显;随后造影剂逐渐退出,肿瘤回声强度从与周围肝实质持平,到低于周围肝实质,最后造影剂完全退出瘤组织,在肝实质增强的背景下呈极低回声。肿瘤强化呈“快进快出”型。结论VX2瘤主要为肝动脉供血,具有恶性肿瘤“快进快出”典型的超声造影增强特点;低机械指数灰阶超声造影能完全反映肝恶性肿瘤血流动力学变化;观察肿瘤的动脉期是超声造影的关键,对诊断及鉴别诊断具有重要意义。

Objective To study the dynamic enhancement changes of VX2 tumor and peri-neoplastic liver parenchyma with gray-scale contrast enhancement. Methods An in vivo animal model was studied using low mechanical index（MI） in conjunction with single-level dynamic contrast-enhanced sonography. SonoVue was applied in eight VX2-bearing rabbits by intravenous bolus injection. Results Low MI grayscale imaging clearly delineated the dynamic enhancement of the tumors and liver parenchyma during the whole phase. All tumors showed hyperechoic enhancement during the early phase and hypoechoic enhancement during the late phase in relation to the hepatic parenchyma throughout the single-level ultrasonographic scans, with the appearance of the tumor vessel preceding that of tumor blush. After contrast agent injection, the tumors were enhanced markedly and display intensity increased rapidly to the peak level. After the arterial phase, the echogenicity of the surrounding liver tissue increased and the intensity of the nodule decreased gradually. Contrast agent was washed out earlier from the tumor than from surrounding liver parenchyma. Conclusions Dynamic contrast-enhanced sonography with low MI level could provide real-time and continuous enhancement in images of the liver and the tumor during the whole phase, and fully delineate the typical enhancement pattern of VX2 tumor, with contrast agents being washed in and washed out quickly relative to the liver parenchyma, due to exclusive dependence on arterial blood supply. It may be useful for the diagnosis of the liver tumor, especially those showing atypical enhancement pattern in biphasic helical CT scanning.