Purpose:To determine the accuracy of single-kidney glomerular filtration rate (GFR) determination using contrastenhanced dynamic magnetic resonance imaging (MRI) and the Rutland-Patlak plot technique. Materials and Methods:Twenty-eight adult patients were included. As reference method, the GFR was measured by plasma clearance using a small bolus injection of iopromide. A three-dimensional gradient-echo (GRE) sequence with a flip angle of 50°was used for MRI; this showed a good linear relationship between gadolinium (Gd)-DTPA concentration and signal change when measured up to a Gd-DTPA concentration of 10 mmol/liter. A slab containing both kidneys and the abdominal aorta was measured 30 times in approximately 3.5 minutes. During this measurement, 15 mL of Gd-DTPA, 0.5 mol/liter diluted to a volume of 60 mL, was injected over 60 seconds. A Rutland-Patlak plot was calculated from the signal changes in the aorta and the renal parenchyma. Single-kidney GFR was calculated for different time windows from the Rutland-Patlak plot slope. Results:The best correlation compared to the reference method was found with the GFR calculated from the slope of the Rutland-Patlak plot 40 -110 seconds postaortic rise. Pearson's correlation coefficient was r ϭ 0.86, SD was 14.8 mL/minute. In many of the patients, a decrease of the renal signal was observed in the excretory phase, which was probably caused by very high Gd-DTPA concentrations in the collecting tubules. Conclusion:Single-kidney GFR can be calculated from dynamic contrast-enhanced MRI. We found a promising correlation of global GFR calculated by MRI compared to the reference method. In any future study, the amount of Gd-DTPA should by reduced to avoid artificial signal drop in the excretory phase induced by the T2* effect.

We determined the optimum gadolinium (Gd)-DTPA dose and time window for calculating the glomerular filtration rate (GFR) using contrast-enhanced (CE) dynamic MRI and the Patlak plot technique. Twelve adult volunteers with healthy kidneys were included in the study. As a reference method the GFR was measured by iopromide plasma clearance. A three-dimensional gradient-echo (GRE) sequence with a flip angle of 50°was used for MRI. Signal was measured using a body surface coil with four elements. Each volunteer was examined on four days using 2 mL, 4 mL, 8 mL, or 16 mL of Gd-DTPA 0.5 mmol/mL dissolved with sodium chloride (NaCl) 0.9% to a total of 60 mL. The injection rate was 1 mL/second. A Patlak plot was calculated from the kidney and aorta signals. The mean reference GFR was 133 mL/min (min-max, 116 -153 mL/min). The best correlation of GFR calculated from MRI data compared to the reference method was found in a time window 30 -90 seconds after aortic signal rise using 16 mL Gd-DTPA. Pearson's correlation coefficient was r ϭ 0.83, and the standard deviation (SD) from the line of regression was 10.5 mL/minute. We found a significantly lower average GFR(MR) using 16 mL Gd-DTPA compared to 4 mL and 2 mL in the late time window 60 -120 seconds post aortic rise. A dose of 16 mL Gd-DTPA was optimal for measuring GFR using dynamic MRI and the Patlak plot technique. The slope should be measured in a time window of 30 -90 seconds post aortic rise.

Using the interstitial space as a third compartment may introduce an error into the measurement of GFR with the Patlak plot technique. We found that the CT protocol in our study resulted in considerable overestimation of GFR as determined with the Patlak plot in patients with increased interstitial space.

Micro CT is feasible for analysis of the coronary artery wall.

CT clearance calculated from data acquired with a minimally modified diagnostic abdominal CT protocol was well correlated with the reference method in determining contrast media clearance for patients without acute renal disorders. The presented method can be used to calculate single kidney contrast media clearance in patients receiving contrast-enhanced abdominal CT for clinical indications.