[Assessment of renal function using low doses of paramagnetic contrast media]

Dynamic MR techniques with Gd-DTPA bolus administration can be used to study renal perfusion and function. In previous studies, the concentration of Gd-DTPA injected was never lower than 0.1 mmol/kg: as a result, depending on the magnetic susceptibility effect, renal signal intensity reduced in the early phases, right after contrast agent injection. To prevent signal intensity from reducing in the early phases, in our study we used a concentration of 0.05 mmol/kg. Qualitative and quantitative evaluations were performed. Seven healthy subjects and 14 patients with different degrees of renal insufficiency were enrolled in the study. All exams were performed using an 0.5-T magnet (Philips Gyroscan T5, II), with 15 mT/m gradient power. Signal intensity measurements at the cortical, external medullary and internal medullary levels, allowed the drawing of curves typical of each degree of renal insufficiency which correlated well with nuclear medicine (scintigraphy) findings. The qualitative evaluation provided results comparable with scintigraphic findings in all 7 normal subjects, in 3 of 4 cases of moderate renal insufficiency, in all 7 cases of moderate/severe renal insufficiency and in the only case of severe renal insufficiency. To conclude, this trial demonstrates the feasibility of MR studies of renal function, which provide morphological and functional pieces of information. Low concentration Gd-DTPA is decisive to avoid the magnetic susceptibility artifacts observed in previous studies.