OBJECTIVETo investigate the sonographic features of the cervical lymph nodes in rabbit VX2 tongue carcinoma model and hyperplasia cervical lymph nodes model using gray scale contrast-enhanced ultrasonography (CEUS) after intravenous administration of SonoVue (a sonographic contrast agent) and to evaluate the potential utility of CEUS in detecting early metastatic cervical lymph nodes in the rabbit VX2 tongue carcinoma model.

METHODSTwenty New Zealand rabbits were placed into 2 groups, 12 for node metastasis and 18 for node hyperplasia. Cervical CEUS was performed in the rabbits of both groups before and after intravenous administration of SonoVue(0.6 ml). The phase, pattern, beginning area and echogenicity of enhancement of the lymph nodes on the right neck were observed and recorded. Dissection of the lymph nodes were guided by the marks made during CEUS and examined histopathologically.

RESULTSOn the right side of each rabbit only one lymph node were detected in both groups. All 8 cases in the hyperplasia group showed homogeneous enhancement starting from central, while in the metastasis group one case showed homogeneous enhancement starting from the central, 3 cases showed inhomogeneous enhancement starting from periphery, and 8 cases showed inhomogeneous enhancement starting both from central and periphery. One lymph node was dissected on the right side of the neck in each rabbit in both groups. Pathological examination showed all 12 lymph nodes in the metastatic group were metastatic lymph nodes, and all 8 lymph nodes in the hyperplasia group were hyperplastic lymph nodes.

CONCLUSIONSAfter intravenous CEUS, metastatic lymph nodes show inhomogeneous enhancement starting from periphery/central or periphery area, while hyperplastic lymph nodes show homogeneous enhancement starting from central area. Metastatic lymph nodes can be characterized as being neoplastic or benign on the basis of the enhancement patterns evaluated by CEUS.