Glomerular filtration rate measurements by dual-injection MR renography

Dynamic contrast-enhanced MR renography, analyzed with appropriate tracer kinetic models [1], is a promising technique for the non-invasive assessment of glomerular filtration rate (GFR). Dual-injection measurements, such as before and after administration of an angiotensin-convertingenzyme (ACE) inhibitor, have been proposed as an improved diagnostic marker of renovascular disease [2]. Technical challenges associated with dualinjection measurements during the same exam include (a) optimization of the injected doses for each of the two measurements and (b) appropriate analysis of the second renography dataset given residual tracer from the first injection. We performed Monte Carlo simulations to determine the optimal distribution of dose for two injections and evaluated the precision of the two GFR values estimated by a 3-compartment tracer kinetic model. A patient study was done to assess reproducibility of GFR measurements after ACE-inhibitor in subjects without renal artery stenosis (RAS).