Delayed Effect of Contrast Enhancement in Brain Tumors on MRI

ABSTRACT

PURPOSE: To evaluate the degree of contrast enhancement of intracranial tumors on delayed (6-8min.) MR imaging after administration of Gd-DTPA. MATERIALS AND METHODS: Both immediate and delayed post-contrast MR imagings were studied prospectively in 35 patients. with brain tumors (11 gliomas, 6 meningiomas, 4 neurinomas, 5 parencymal metastases, 5 hemangioblastoma, 4 others) at either 0.5 T or 2.0 T unit. After precontrast TI-, proton-density, and T2-weighted spin echo images were obtained, each patient underwent Tl-weighted imaging immediately following infusion of 0.1 mmol/Kg of Gd-DTPA. Subsequently, the second postcontrast Tl-weighted images were obtained with no additional injection of the contrast media. Time-interval between the postcontrast immediate and the delayed images was approximately 6-8 minutes. Degree of contrast enhancement of the lesions was assessed both visually and quantitatively. For quantitative study, contrast enhancement ratio(CER) of tumors was calculated in both immediate and delayed post-contrast images. RESULTS: There was stronger visual enhancement in 7 of 11 cases with gliomas and 3 of 5 cases with parenchymal metastasis on delayed images when compared with immediate images, whereas all 10 cases of extraaxial tumors(meningiomas and neurinomas) showed decreased enhancement on delayed images. Quantitatively, mean CERs of gliomas and metastases were higher on delayed study than on immediate study by 20. 5% and 49.2%, respectively. Extraaxial tumors showed decrease of CER on delayed study by 19.7% as compared with that of immediate study. Hemangioblastomas showed visually poor enhancement on delayed image in 4 cases and equal enhancement on both immediate and delayed images in remaining one case, and quantitatively demonstrated decrease of CER on delayed study by 15.4%. CONCLUSION: Since there was more conspicuous contrast enhancement in many intraaxial tumors such as gliomas and metastases on 6-8 minutes delayed post-contrast MR study, the delayed post-contrast study may be needed in some intraaxial tumors for their characterization, and may also be helpful for the differential diagnosis between intraaxial and extraaxial tumors.