In vitro evaluation of a mechanical injector for infusion of magnetic resonance contrast media

The authors evaluated the performance of a prototype mechanical injector developed for infusion of magnetic resonance (MR) contrast media. The injector was installed in a 0.6-T clinical MR scanner, and evaluation was made using saline (viscosity: 1.0 cP) and gadopentetate dimeglumine (viscosity: 4.9 cP) with 16-, 21-, and 25-gauge needles, and 244- and 366-cm connecting tubing. At a fixed flow rate of 1 mL/second, volume infused was within 10% of the desired volume except for infusions less than 1 mL. Reproduction of flow rates was less reliable. With saline, maximal flow rates were 5.5 mL/second, 4.2 mL/second, and 1.1 mL/second for the 16-, 21-, and 25-gauge needles, respectively, and 3.7 mL/second, 2.4 mL/second, and 0.9 mL/second, respectively, for gadopentetate dimeglumine. Needle size was identified as the major factor limiting flow rate. The magnet was reshimmed after the injector was installed, and no deleterious effects were identified on gradient echo (TR: 250/TE:18/flip angle 60 degrees) MR images.