Glioblastoma multiforme: MR imaging at 1.5 and 9.4 T after injection of polylysine-DTPA-Gd in rats.

Polylysine-DTPA-Gd, a new MR contrast agent, was injected into the aorta of rats 7 days after C6 glioblastoma was implanted in their brains; MR imaging was performed 3 days later. The imaging was done at two field strengths: (1) 1.5 T with a 3-mm slice thickness and in-plane resolutions of 600 microns and (2) 9.4 T with a 125- or 500-microns slice thickness and in-plane resolutions of 95 microns. In animals injected with polylysine-DTPA-Gd (1 microgram or more per rat), the T1-weighted images and mixed T1, T2 images of the C6 glioblastoma revealed a higher signal intensity at the marginal region between tumor and normal brain than that seen in surrounding normal brain. The central tumor region had a low signal intensity. The concentration of Gd in the C6 glioblastoma, after injection of 1 microgram polylysine-DTPA-Gd per rat, was calculated to be 0.14 mumol/l. The central tumor region also had a low signal intensity in animals that were not injected with the contrast agent, but the margin between tumor and normal brain was resolved poorly, if at all. The polylysine-DTPA-Gd revealed the microvasculature of the C6 glioblastoma in the 125-micron-thick slices obtained at 9.4 T. This is the first study to reveal the utility of the 9.4-T MR imager for examination of glioblastomas in situ and to demonstrate the utility of polylysine-DTPA-Gd as a contrast agent for the definition of the margin between glioblastoma and normal brain tissue.