Pharmacokinetics of three gadolinium chelates with different molecular sizes shortly after intravenous injection in rabbits - Relevance to MR angiography

RATIONALE AND OBJECTIVES. TO mimic an MR angiographic protocol, an experime ntal model was developed in rabbits to determine gadolinium concentrations in blood early after injection. Contrast agents with different molecular si zes were compared. METHODS. The influence of injection parameters (injection rate, duration of injection, volume of injection, dose) was assessed, and two blood pool age nts (P760, P717) were compared with the low-molecular-weight Gd-DOTA under similar conditions. RESULTS. Two main phases were identified: bolus and postbolus, Injection pa rameters strongly influenced the pattern of the bolus phase, but the postbo lus phase was sensitive only to the injected dose. The blood pool agents pr esented a bolus phase profile similar to that of Gd-DOTA, but 45 seconds af ter injection, 84% of P717 molecules were still present in the blood compar tment, compared with 65% of P760 molecules and only 51% of Gd-DOTA molecule s. CONCLUSIONS. Blood pool agents are useful for MR angiographic protocols inv olving the postbolus phase. In protocols in which only the bolus phase is i maged, blood pool agents provide similar data to Gd-DOTA, provided that the injection rate, iso-T1 efficiency dose, and volume are similar.