MR PERFUSION IMAGING OF THE KIDNEY PREDIPYRIDAMOLE AND POSTDIPYRIDAMOLE STRESS

Animal studies have demonstrated that renal MR contrast enhancement de pends on the timing of image acquisition. Limited human studies have d emonstrated effects of dipyridamole (DP) on total renal perfusion, Thi s study assessed the effect of DP on total and regional rend perfusion using gated perfusion MRI for patients undergoing DP stress, Five sub jects with no evidence of renal ischemia were examined at rest sind af ter DP stress. Rest MRI, images in the left kidney were acquired using electrocardiogram (ECG)-gated MR: turbo fast low-angle shot (FLASH); echo time (TE) = 12, repetition time (TR) = 6, flip angle = 12, invers ion time (TI) = 100) 10 to 45 seconds after injection of gadopentetate dimeglumine, Stress was induced in the MRI scanner (DP, .56 mg/kg ove r 4 minutes) followed by stress MRI after a second bolus of gadopentet ate dimeglumine in the same position and identical time intervals, MR signal in the whole left kidney and renal medulla and cortex pre- and post-DP demonstrated a 70% depression of total renal perfusion with re lative preservation of cortical perfusion at the expense of medullary perfusion, Past-DP MR images demonstrated a decrease in cortical perfu sion with an additional 29% depression of medullary perfusion (P < .00 1) with respect to cortical perfusion. Turbo FLASH MRI can provide ade quate time and spatial resolution to demonstrate changes in renal perf usion, Depression of renal medullary perfusion after DP appears to be caused by the intrarenal effect of DP and may have clinical impact.