[Assessment of retropharyngeal lymph node by comparing CT with MRI]

The incidence of nasopharyngeal carcinoma (NPC) is high as part of malignancy of head and neck in South China. Some of the foreign radiologists investigated on it by comparing CT (computed tomography) with MRI (magnetic resonance imaging), but there was no description for metastatic retropharyngeal lymph node (RPN) of NPC. None of this kind of article published in domestic. The current study was designed to evaluate CT and MRI in identifying retropharyngeal node by comparing the finding of CT and MRI in 56 patients with NPC.

Fifty-six cases pathologically proven as nasopharyngeal carcinoma were selected from August, 1993 to December, 2000; CT scan were performed by Elscient CT Twin flash, axial scan were parallel to the OM line routinely from soft palate to the supracellar cistern. MRI scan were performed by Philip T5-II super-conducting magnetic resonance imaging system(0.5T). The standard quadrature head coil was used. Routine axial, saggital, and coronal scan with SE sequences were obtained. Scanned field ranged from soft palate to the supracellar cistern. After plain scaned, contrast material were administrated in 40 cases by intravenous injection of Gd-DTPA 0.1 mmol per kilogram body weight. And then repeat axial, saggital and coronal scan.

MRI recovered the RPN more exactly than CT (13 cases by CT and 24 cases by MRI) and there was significant differentiation 0(P < 0.05). It is possible to distinguish the metastatic RPN of NPC from the directly infiltration of tumor by MRI.

MRI is more precise than CT in differentiating the RPN from the directly invasion by tumor tissue of NPC, which will affects the 92 Chinese staging systems, for NPC obviously.