Diffusion-weighted imaging and fluid attenuated inversion recovery imagingin the evaluation of primitive neuroectodermal tumors

The aim of our study was to determine whether fluid-attenuated inversion re covery (FLAIR) imaging and diffusion-weighted imaging (DWI) would be helpfu l in characterizing primitive neuroectodermal tumors (PNET) from other pedi atric brain tumors. We expected that the compact cellular nature and the re latively small extracellular space of this tumor would affect the signal in tensity on both pulse sequences relative to the more sparsely cellular glia l tumors that have larger extracellular spaces. Eighteen pediatric patients with PNET were examined on a 1.5 T MRI with routine imaging plus FLAIR and compared with 28 patients with non-PNET. DWI was also performed in 7 PNET and 18 non-PNET. Seventy-eight percent of PNET were isointense to gray matt er on FLAIR while 82% of non-PNET were hyperintense and only one was isoint ense (3 %). Diffusion was abnormally restricted in all 7 PNET examined (100 %) but was restricted in non-PNET in only 1 out of 18 (6 %) patients who h ad DWI. The differences in the histologic architecture between PNET and non -PNET are reflected in both FLAIR imaging and in DWI.