Effect of exposure to gadodiamide and brain irradiation on T₁-weighted images and ADC maps of the dentate nucleus

Background Brain irradiation is considered a cofactor influencing the dentate nucleus (DN) signal intensity (SI) on unenhanced T-1-weighted images in patients exposed to gadolinium-based contrast agents (GBCAs). Purpose To assess the effect of gadodiamide and whole-brain radiation therapy (WBRT) on T-1-weighted images and on apparent diffusion coefficient (ADC) maps of DN. Study Type Single-center retrospective. Population In all, 125 patients who underwent brain MRIs were classified into four groups: 1) patients who did neither receive intravenous GBCAs injections nor irradiation (controls); 2) patients having >= 3 GBCAs-enhanced scans and no WBRT; 3) patients having WBRT and < 3 GBCAs-enhanced scans; and 4) patients having WBRT and >= 3 GBCAs-enhanced scans. Field Strength/Sequence 1.5T magnet, echo-planar diffusion weighted imaging (DWI) and unenhanced T-1-weighted sequences. Assessment The DN-to-pons SI ratio on unenhanced T-1-weighted images and ADC values of the DN were calculated. Values were compared between groups and relative to the cumulative gadolinium dose and to the time delay after WBRT. Statistical Tests Statistical analysis included the Mann-Whitney U-test and Spearman's rank-order correlation. Results DN ADC values were not significantly different (P = 0.34) between patients exposed to gadodiamide (0.81 +/- 0.06) and controls (0.83 +/- 0.07). There were no differences in DN ADC values (P = 0.28) and DN-to-pons SI ratios (P = 0.42) between patients exposed to WBRT (ADC values: 0.85 +/- 0.09; SI ratio: 1.11 +/- 0.10) and controls (ADC values: 0.83 +/- 0.06; SI ratio: 1.09 +/- 0.06). There was a significant negative correlation between DN ADC values and the time (days) since the end of WBRT (r = - 0.33; 95% confidence interval [CI]: -0.55, -0.06; P < 0.05). Data Conclusion We did not find changes suggestive of gadolinium-related tissue microstructural damage of the DN. The ADC values of the DN are associated with the time from WBRT. Level of Evidence 3 Technical Efficacy Stage 5