Contrast Enhancement in Spinal MR Imaging 633

We evaluated 44 patients with suspected spinal tumors or previous laminectomies with gadolinium-DTPA MR imaging in order to characterize the enhancement in normal, postoperative, and neoplastic intraspinal tissue. Using the signal intensity of CSF as an internal control, we calculated the percentage increase in signal intensity from pre-to postgadolinium studies. Tumors (astrocytoma, ependymoma, schwannoma) enhanced 70-350%; epidural scar, normal epidural venous plexus, and dorsal root ganglion enhanced up to 200%. Contrast enhancement does not per se distinguish neoplastic from normal tissue. Enhancement with gadolinium-DTPA appeared to increase the conspicuousness of intramedullary tumors but not intraosseous metastases. We believe that gadolinium-enhanced MR imaging is a valuable adjunct to routine MR imaging in the evaluation of intraspinal neoplastic processes and may be useful in delineating normal and postoperative structures in the spinal canal. Gadolinium (Gd)-DTPA is under evaluation by the FDA as a contrast medium tor MR imaging of the spine. Enhancement of spinal tumors has been shown previously Materials and Methods Forty-two patients were studied under two different phase Ill protocol s. In one protocol (group 1), 22 patients with suspected spinal tumors were studied. Of the 22 enrolled, 15 had surgical or postmortem verification of the diagnosis. Among these patients there were th ree astrocytomas, three ependymomas, three schwannomas, two metastases , and four cysts not associated with a tumor. One of the 15 patients had previously undergone resection of an ependymoma and was evaluated for a presumed recurrence but has not yet been reoperated . Four of the 22 patients had negative MR studies without anatomic confirmation, and three had positive studies . In a second protocol (group II), 20 patients who had previously undergone laminectomy were studied to investigate possible scar tissue or recurrent disk herniations. Eight patients with MR evidence of epidural scar at one or more levels had surgical confirmation of epidural scar (with or without herniated disk). Measurements of contrast enhancement were made in the 14 tumor tissues in group I, in epidural scar in group II , and in normal tissues in both groups. MR was performed on a 1.5-T cryogenic imager with surface coil s. Each patient had sagittal or axial images with 800/20/2 (TR /TE jexcitations) , then with 2500/25/2 and 2500/ 80/2 plus additional images as needed. Gd-DTPA was injected intravenously in a dose of 0.1 mmjkg body weight. The 800/20 images were then repeated in the same planes with the same number of acquisitions, field of view , and so on. Transmit and receive attenuation were optimized with the system 's automatic tuning software for both pre-and post-Gd-DTPA acquisitions. The signal intensity was measured in reg ions of interest in the images pre-and post-Gd-DTPA. The signal intensity of CSF (which was assumed not to enhanc