Verification of Quantification of Quantitative Susceptibility Mapping for Estimating the Amount of Gadolinium Deposited in the Brain: a Preliminary Phantom Study

Abstract

This study aimed to clarify the effects of different types of gadolinium (Gd)-based contrast agents (GBCAs) and different T1 values of Gd-containing materials on the R1 value and magnetic susceptibility of quantitative susceptibility mapping (QSM). GBCA dilution phantoms were prepared using five types to of GBCA evaluate their effects. The effect of different T1 values of substances with Gd was assessed. A 3.0 T-MR scanner with a 20-channel head/neck coil was used to acquire the R1 map and QSM for the phantom. Linear regression analysis was performed to evaluate the relationship between Gd concentration and R1 or magnetic susceptibility for each phantom. An analysis of covariance (ANCOVA) was employed to assess the consistency of the slopes. Linear regression analysis showed that Gd concentration had a high coefficient of determination for R1 values and magnetic susceptibility (R², 0.696–0.999; p < 0.001). ANCOVA showed significant differences in the slopes of R1 values when different GBCA types were used (p < 0.001), but no significant differences in the slopes for magnetic susceptibility (p = 0.719). Differences in surrounding T1 values significantly altered the intercepts and slopes of the measurements of R1 values and magnetic susceptibility (p < 0.001). The change in slope was smaller for magnetic susceptibility than for R1 values. Thus, while R1 was minimally affected by the GBCA type, it varied with surrounding tissue T1 values. QSM, however, was unaffected by the GBCA type and less influenced by T1 values, suggesting QSM may offer more quantitative measurements of Gd compared to R1 maps.