[Imaging of sacral chordoma: comparison between MRI and CT]

Sacral chordoma is a primarily benign tumor with a high tendency to recur. A correct definition of tumor volume is a significant prognostic factor. We compared the value of CT and MRI in diagnosing a sacral chordoma.

31 patients with a histologically proven sacral chordoma were included in this study. Following parameters were analyzed by two independent radiologists: septation, signs of blood and ossification in the tumor tissue, contrast enhancement, maximal tumor diameter, infiltration of the soft tissue, the dural salc and the cauda equina and multifocality.

In CT all chordomas showed a hypodensity to the normal tissue and in MRI a hyperintensity on T2w images with a low level of contrast enhancement. On the basis of the more precise soft tissue contrast of MRI compared with CT, MRI was significantly more accurate in all tested parameters (p <0.05) besides in detecting tumor ossification. In CT tumor volume was frequently underestimated.

MRI in sacral chordoma is an essential tool in the pretherapeutic diagnostic regimen and in a state of relapse.