Effect of Echo Time on the Maximum Relationship between Contrast Agent Concentration and Signal Intensity Using FLAIR Sequence

Contrast-enhanced fluid-attenuated inversion recovery (FLAIR) is one of the MRI sequences that can be used for detection and evaluation of pathological changes in the brain. In this work, we have studied the effect of different echo times (TE) on the maximum relationship between signal intensity and concentration of the contrast agent using the FLAIR sequence. For assessment of the relationship between signal intensity (SI) and concentration, a water-filled phantom containing vials of different concentrations of Gd-DTPA (0 to 19.77 mmol/L) was used. The mean SI was obtained in the region of interest when T1-weighted images were implemnted. The SI was corrected for coil non-uniformity. This study showed that an increase in TE is associated with a decrease in the maximum relationship between SI and concentration. TE is an important parameter when the SI is measured in clinical FLAIR studies. The concentration leading to a maximum SI depends on this parameter, with the relevant concentration range decreasing at high TE.