Accuracy of iodinated contrast and saline delivery using a piston-driven and a peristaltic power injector in CT—an in vitro study

Abstract Objective To evaluate the accuracy of iodinated contrast media (ICM) and saline flush volumes delivered by a piston- and a peristaltic-based injector in an in vitro study. Materials and methods Seven clinical injection protocols, ranging from pediatric to bariatric indications and incorporating varying flow rates, ICM volumes, saline volumes, and dilution ratios, were tested. Identical prescriptions were programmed into a piston-based injector and a peristaltic-based injector. Injections were performed into vials. Calibration samples (5–20 mgI/mL) were scanned on a multi-slice CT scanner to generate a calibration curve relating CT number to iodine concentration. The saline test volume and combined ICM + saline flush volume were measured for each injection. CT numbers of mixtures were converted to iodine concentration using the calibration curve, and delivered ICM and saline volumes were calculated. Percent errors between expected and measured volumes were determined. A Wilcoxon signed-rank test assessed statistical significance. Results For the peristaltic-based injector, ICM volume error ranged from 4.0% to 10.0% and saline flush error from 0.6% to 9.2%. For the piston-based injector, ICM volume error ranged from 9.9% to 40.0% and saline flush error from 1.5% to 50.2%. Differences between expected and delivered volumes were statistically significant across protocols ( p = 0.031/= 0.035), except for peristaltic saline flush protocols (Ped 12 mL ( p = 0.094), Adult 170 mL ( p = 0.156), and High Flow ( p = 0.093)). Conclusions Both injectors delivered excess ICM while saline flush volumes showed variability. These findings underscore the importance of performance verification to ensure accurate and consistent contrast delivery in clinical practice. Key Points Question Automated injectors often delivered more contrast than expected. Findings Both systems often underdelivered saline with some instances of overdelivery. Relevance statement Unrecognized variability in contrast and saline delivery across different injection settings may affect enhancement consistency, contrast exposure, and diagnostic reliability. Broader injector performance evaluation across clinically used protocols and clinically simulated setups may improve CT practice.