The Effect of Gadolinium on Synthetic Magnetic Resonance Quantitative Imaging

Synthetic (Sy) MRI is a clinically approved technique providing quantitative MRI measures based on T₁-weighted, T₂-weighted, and proton density relaxometry. MRI sequences are often acquired after contrast injection with gadolinium (Gd) to assess active lesions in persons with multiple sclerosis (PwMS), affecting relaxation time. We aimed to assess the influence of Gd on the SyMRI-based volumetrics in PwMS.

We enrolled 106 PwMS and 15 controls who performed pre-/post-contrast brain SyMRI on a 3T scanner. We evaluated mean change in brain parenchymal fraction (BPF), white matter (WM), grey matter (GM), myelin (Myl), non-aqueous component (NAC), excess parenchymal water (EPW), and T₁ enhancement (T₁E) using paired sample t-test for pre-/post-Gd volumes and independent sample t-test for comparison between groups.

The mean age was 40.9 and 39.9 years with 69% and 87% females in MS and controls, respectively. Compared to native volumetrics, Gd caused a significant observed volume increase (p < 0.001) in BPF 1.05 ± 0.3%, WM 2.8 ± 0.99%, Myl 1.42 ± 0.39%, NAC 1.04 ± 0.23%, and EPW 0.6 ± 0.4% and decrease in GM -3.05 ± 1.34% in MS. Similar change was seen in controls: BPF 0.99 ± 0.21%, WM 2.94 ± 0.93%, Myl 1.35 ± 0.37%, NAC 0.99 ± 0.22%, EPW 0.47 ± 0.29%, and GM -2.89 ± 1.18%. The change in T₁E was 0.05 ± 0.12% in MS (p < 0.001) and 0.02 ± 0.25% (p = 0.76) in controls. The number of contrast-enhancing lesions correlated with T₁E (r = 0.348, p < 0.003).

There was a consistent pattern of volume changes in PwMS and controls, except for T₁E, where the contrast could have affected the results in PwMS. Therefore, combining pre- and post-contrast metrics in longitudinal studies should be interpreted with caution.