Differentiating between T1 and T2* changes caused by gadopentetate dimeglumine in the kidney by using a double-echo dynamic MR imaging sequence.

Dynamic MR images of the passage of gadopentetate dimeglumine through the kidneys of normal rats are obtained using a dual gradient-echo sequence. The amplitudes of gradient echoes are defined by local T1 and T2* values in the tissue. The ratio of these amplitudes, primarily defined by local T2*, can be used to differentiate between T1 and T2* effects. This is particularly important with regard to renal studies because, due to a highly inhomogeneous distribution of gadopentetate dimeglumine in the kidney, T2* shortening can impede MR data analysis. To study changes in the observed signal caused by gadopentetate dimeglumine, curves of MR renal intensity versus time were obtained in the cortex and medulla after administration of the contrast agent. Using T2* compensation, distinct temporal peaks were observed in the cortex and outer medulla, indicating a high concentration of gadopentetate dimeglumine in the vascular phase. The authors conclude that this technique can be a useful tool for studying renal function noninvasively.