Delayed computed tomography contrast enhancement patterns in biopsy proven cases

After a stereotactic brain biopsy of intracranial lesions, many neurosurgeons routinely obtain a noncontrast computed tomographic scan to rule out hemorrhage. We have observed there is often a significant delayed contrast enhancement on this postoperative scan, and the pattern of this enhancement frequently differs from the preoperative pattern. To assess these changes and to determine if they are related to lesion pathology or other clinical factors, the pre- and postoperative scans of 89 patients who underwent stereotactic biopsies were reviewed. Despite an average time delay of 153 minutes between scans, 81% of the lesions enhanced similarly or better on the postbiopsy image. One lesion enhanced only on the postoperative image, and in two cases, new lesions were seen postoperatively. Ring and other enhancing lesions tended to fill in with time, becoming homogeneous. The area of contrast enhancement increased in 83%. The borders of the lesions tended to become less sharp with time. No patterns of delayed enhancement, which give histologically definitive diagnostic information, were found. The tendency toward an increased area of contrast enhancement with time suggests that computed tomographic scans taken at the time of contrast injection may not show the true extent of the lesion. For patients undergoing computed tomography-guided stereotactic biopsies or radiosurgery of poorly enhancing lesions, the localization scan might be delayed after the administration of contrast medium to improve resolution and target selection.