Bolus injection of MR contrast agents: hemodynamic effects evaluated by intracerebral laser Doppler flowmetry in rats.

PURPOSE To determine the effects on arterial blood pressure and cerebral blood flow of intravenous bolus injection of three MR contrast agents: gadopentetate dimeglumine, polylysine-Gd-DTPA, and superparamagnetic iron particles (SPIO). METHODS A single-fiber laser Doppler flowmetry probe was placed intracerebrally in 56 anesthetized rats. Cerebral blood flow and mean arterial blood pressure were measured before (baseline), during, and up to 30 minutes after intravenous bolus administration of the three contrast agents: 0.1 mmol/kg and 0.3 mmol/kg gadopentetate dimeglumine (n = 18 per group), 0.3 mmol/kg polylysine-Gd-DTPA (n = 10), and 0.03 mmol/kg SPIO (n = 10). RESULTS Neither the higher nor lower dose of gadopentetate dimeglumine had any statistically significant effect on cerebral blood flow, and there was no change in blood pressure during administration of either dose of gadopentetate dimeglumine. Administration of polylysine-Gd-DTPA caused a transient drop in blood pressure in two animals, marked in one (decrease to 21% of baseline values) and mild in the other (84% of baseline). After administration of SPIO, a significant decrease in blood pressure occurred in one animal (41% of baseline). Despite this decrease in mean arterial blood pressure, there were no statistically significant changes in cerebral blood flow after administration of polylysine-Gd-DTPA or SPIO. CONCLUSION Our results suggest that bolus injection of these contrast agents at clinically relevant doses causes no significant alteration in cerebral blood flow. We conclude that gadopentetate dimeglumine is well suited for cerebral MR perfusion imaging without inherent influence on cerebral blood flow and that the same is probably true for polylysine-Gd-DTPA and SPIO.