MR-based renography as a replacement for radionuclide diagnostic studies

This study explores the importance of the partial volume effect (PVE) in quantifying renal function on magnetic dynamic contrast enhanced magnetic resonance imaging (DCE- MRI). DCE-MRI image data were acquired for a healthy volunteer and after motion correction a PV correction step was applied to remove non-renal contributions to time-intensity curves derived from a typical renal cortical region of interest (ROI). PV correction consisted on the assignment of a mixing vector to each voxel location, representing the contributions of each tissue into a given voxel due to the convolution action of the point spread function (PSF) of the acquisition sequence. These mixing vectors were then used to recover the true intensities that correspond to the unmixed (i.e. pure) signals associated with each constituent tissue, eliminating contributions from liver, spleen and other surrounding tissues from the renal component. The result was an increased slope in the filtration part of the enhancement curve for the renal component. Quantitatively, PV correction resulted in an increase of glomerular filtration rate (GFR) estimated through a Rutland-Patlak analysis. Using a common DCE-MRI sequence, the contribution to a typical renal cortical ROI from non-renal tissues was found to be ~ 25%. The removal of these component resulted in a 32% (left) and 37% (right kidney) increase in relative GFR and an increased R2 for the Rutland Patlak model compared to the same analysis undertaken with no PVE correction.