Optimization of flushing strategies to minimize dilution of high-concentration radiopharmaceuticals in intravenous tubing.

backgroundIn precise imaging techniques such as dynamic imaging with radiopharmaceuticals, achieving a high-concentration bolus in target sites is crucial. However, dilution within infusion tubing severely compromises bolus integrity. Although pulsed flushing is clinically used to clear intravenous tubing, its efficacy in mitigating radiopharmaceutical dilution and the optimal protocol parameters remain insufficiently elucidated.

methodsThis study employed a theoretical analysis of dilution mechanisms and utilized computational fluid dynamics simulations to compare the efficacy of pulsed flushing with different volumes and frequencies, verifying its feasibility. Subsequently, in vivo rat pharmacokinetic experiments were performed to systematically assess the pulsed flushing strategy.

resultsTheoretical and computational fluid dynamics analyses indicate that while higher continuous flow rates shorten injection time, it exacerbates the "tailing" phenomenon caused by parabolic flow patterns. In contrast, a high frequency, small-volume pulsed flushing strategy generates a greater number of vortices at abrupt cross-section changes in the tubing during injection pauses, effectively clearing residual drug and thereby significantly suppressing axial dispersion of the bolus. Compared to continuous flushing, pulsed flushing demonstrates superior performance in reducing the final residual rate and controlling tailing. In vivo experiments in rats further confirmed that, compared to manual operation, the automated pulsed flushing strategy produces boluses with better morphology during the initial injection phase, exhibits greater consistency both between and within individuals, and leaves no radioactive residue at the puncture site.

conclusionHigh frequency, small-volume pulsed flushing is an effective strategy for clearing dead space and suppressing the tubing dilution effect through vortex induction, outperforming traditional manual and continuous automatic injection. Appropriate selection of pulse bolus volume parameters is the core solution for overcoming the dilution challenge in automatic bolus injection and for improving injection consistency.