Effect of intravenous gadolinium-DTPA on diffusion tensor MR imaging for the evaluation of brain tumors.

INTRODUCTION: The aim of this study was to investigate whether indices of diffusion tensor MRI (DT-MRI) are altered after contrast medium injection in patients with brain tumors.
METHODS: DT-MRIs at a 3-T unit before and 6 min after gadolinium-diethylenetriamine penta-acetic acid injection were obtained in nine patients (five women, four men) with histologically confirmed brain tumors (four metastases, one glioblastoma multiforme, three meningiomas, and one lymphoma). Fractional anisotropy (FA), trace and mean raw DT-MRI data without (DT_b0, b value = 0 s/mm(2)) and with (DT_b800, b value = 800 s/mm(2)) diffusion-encoded gradients were calculated. Regions of interest (ROIs) were placed in the tumor, peritumoral edema, and normal-appearing symmetric contralateral brain tissue for each patient. The Kruskal-Wallis rank sum test was used to determine the effects of contrast medium and ROI for all of the maps, and the Wilcoxon signed-rank test was performed for either paired t test between pre- and post-contrast values of DTI indices for the ROIs or the post hoc test.
RESULTS: Statistically significant differences between pre-contrast and post-contrast DT-MRI are shown in the trace value of the peritumoral edema area (p = 0.0195) and the FA value of the tumor area (p = 0.0273). Trace and FA values of the other areas show no statistically significant differences between pre- and post-contrast (p > 0.05). In addition, we find a significant ROI effect for both FA (chi (2) = 26.514, df = 2, p = 0.0001) and trace (chi (2) = 21.218, df = 2, p = 0.0001).
CONCLUSION: DT-MRI obtained after contrast medium injection of 6 min results in significant changes in diffusion isotropic and anisotropic values. Therefore, clinical applications of DT-MRI after administrating a contrast medium require caution in interpretation.