Paramagnetic contrast enhancement at 0.02 T: an experimental study using Gd-DOTA in normal and hydronephrotic kidneys

Both normal and experimentally hydronephrotic rabbits were imaged at 0.02 T using partial saturation (PS 160/30) and inversion recovery (IR 1000/200/40) sequences. The signal intensity of normal renal medulla and cortex markedly increased after the injection of 0.1 mmol/kg of Gd-DOTA. In the unilateral total hydronephrosis the dilated renal pelvis did not contrast enhance after 15 and 35 min of Gd-DOTA injection. The enhancement pattern was similar in 1- and 3-week-old hydronephrosis. The effect of Gd-DOTA on renal T1 times at 0.02 T was studied using rats. Fifteen minutes after the Gd-DOTA injection (0.1 mmol/kg) the T1 times of excised rat kidneys decreased from 311 to 90 ms. The authors conclude that the enhancement of the MR signal of the kidney by Gd-DOTA at an ultralow magnetic field (0.02 T) is similar to its enhancement at higher fields (greater than 0.15 T).