Differences in contrast enhancement between intra- and extra-axial lesions after two hours of iodine injection

In order to try to improve discrimination between the brain lesions that produce damage to the brain-blood barrier and those which are irrigated by extracerebral vessels, the behavior of contrast enhancement up to two hours after iodine injection was studied in two groups of patients. Eight patients had extra-axial lesions (7 meningiomas, one acoustic neuroma) and eleven had intra-axial lesions (6 of astrocytic type, 3 metastases, 2 inflammatory). In the first group, mean values of the lesioned areas in HU decreased progressively with time. However, in many cases in the second group the values at the end of the study were equal to or higher than those observed immediately after contrast medium injection. Highly significant differences were observed between the two groups. The contrast medium in the intra-axial lesions conform to the behavior of all other fluids in a damaged barrier, remaining for a very long time in the interstitial space. In the extra-axial lesions, the contrast moved freely and the return from the interstitial to the intravascular space was also unobstructed, since values decayed immediately after injection. For these reasons, the observation of scans after two hours of contrast injection might be useful for differential diagnosis in those cases where doubt exists.