The effect of inversion times on the minimum signal intensity of the contrast agent concentration using inversion recovery t1-weighted fast imaging sequence

Background: Inversion recovery (IR) pulse sequences can generate T1-weighted images with a different range of inversion time (TI) to suppress or null the signal intensity (SI) for a specified tissue. In this study, we aimed to investigate the effect of TI values on the concentration of the contrast agent, which leads to a minimum signal intensity, using an inversion recovery T1-weighted 3-dimensional fast-gradient echo imaging sequence. Methods: A phantom was designed to hold 25 vials which contained different (between 0 and 19.77mmol/L of (Gd-DTPA)) concentrations of the contrast agent. We used the vials of different concentrations to measure SI using IR sequences with different inversion times (TI, 100-3000ms). Results: The results of this study revealed that the T1 recovery curve did not cross the x- axis for the lower TI. Therefore, a minimum SI can be observed from the concentration of the contrast agent versus SI curves. The findings of this study also revealed that the concentration of the contrast agent, which leads to a minimum SI, is dependent on the TI and the minimum SI will be increased at higher TI concentrations. Conclusion: In conclusion, when the TI parameter is used to suppress the SI of the specified tissues in clinical studies (e.g., fat suppression or blood suppression in perfusion measurements), it should be chosen with great caution.