Surgically induced intracranial contrast enhancement: Potential source of diagnostic error in intraoperative MR imaging

BACKGROUND AND PURPOSE: Intraoperative MR imaging is being used increasingl y during neurosurgical interventions. The aim of this study was to describe and classify different forms of surgically induced intracranial contrast e nhancement observed during intraoperative MR examinations. METHODS: A total of 51 intraoperative MR examinations were performed to ass ess the extent of brain tumor removal. The intraoperative MR results (T1-we ighted images, unenhanced and obtained serially after the IV administration of paramagnetic contrast material) were compared with preoperative and ear ly postoperative MR findings. Animal experiments were conducted to obtain f urther evidence of the mechanism of surgically induced contrast enhancement . RESULTS: Four different types of surgically induced contrast enhancement we re found: meningeal enhancement, increased enhancement of the choroid plexu s, delayed enhancement at the resection margins, and immediate intraparench ymal contrast enhancement. The types of surgically induced contrast enhance ment differ regarding their location, configuration, and time course. Their potential to be confused with contrast-enhancing, residual tumor also vari es, Three of the four types of surgically induced contrast enhancement were reproducible in an animal model. CONCLUSION: Surgically induced contrast enhancement is a potential source o f error in intraoperative MR imaging, Careful analysis of the location, con figuration, and time course of intraoperatively observed intracranial enhan cement is critical to avoid confusing surgically induced contrast enhanceme nt with contrast-enhancing, residual tumor.