Practical in-syringe mixing method for uniform particle delivery during embolization procedures.

Embolic particles settle out of suspension inside syringes over time, leading to nonuniform particle delivery. A stepper motor stator was placed around a syringe containing a magnetic agitator to provide easily programmable rotating magnetic fields that result in the stirring of suspensions within the syringe. Injection uniformity was evaluated using a microscope, which recorded particle flow resulting from injections with and without mixing. Increasing delay times between initial uniform suspension and injection allowed particles to settle, which caused up to sixfold reductions in injection uniformity across all injection rates (1, 5, 10 mL/min), with particle boluses often ejected near the end of an injection. In-syringe mixing provided a fourfold improvement in injection uniformity at all injection flow rates following long delay times (120 s); at slow injection rates (1 mL/min), mixing provided better uniformity than all injections performed without mixing. Mixing performance was optimized by using moderate agitator rotation rates (~ 10 revolutions per second) and frequent changes in rotation direction (~ every 250 ms). This compact solution for maintaining and injecting uniform embolic suspensions prevents particle settling, reduces variability during injections, and has applications in both clinical and research settings.