High resolution susceptibility weighted MR-imaging of brain tumors during the application of a gaseous agent

Purpose: To employ a high resolution blood oxygenation level dependent (BOLD) method called susceptibility weighted imaging (SWI) together with the breathing of carbogen to investigate the response of cerebral tumors to this breathing gas and to assess tumor anatomy at high resolution. Methods: Five patients with cerebral tumors (four glioblastoma multiforme, one astrocytoma [WHO grade II]) were studied using a susceptibility weighted 3D gradient echo, first order velocity compensated sequence (TE=45 ms, TR=67 ms, alpha =25 degrees, FOV=256 x 192 x 64 mm(3), typical matrix =512 x 192 x 64), on a 1.5 T MR scanner while they were breathing air and carbogen. Signal changes between the two breathing conditions were investigated. Results: The glioblastomas showed strong but heterogeneous signal changes between carbogen and air breathing, with changes between +22.4 +/- 4.9% at the perimeter of the tumors and -5.0 +/- 0.4% in peritumoral areas that appeared hyperintense on T-2-weighted images. The astrocytoma displayed a signal decrease during carbogen breathing (-4.1 +/- 0.1% to -6.8 +/- 0.3% in peritumoral areas that correspond to hyperintense regions on T-2-weighted images, and -3.1 +/- 0.1% in the tumor-center). Conclusions: SWI provides high resolution images of cerebral anatomy and venous vascularization. Combined with hypercapnia it allows for regional assessment of tumor activity.