Optimize scan timing in abdominal multiphase CT: Bolus tracking with an individualized post-trigger delay

Abstract

Purpose: To conduct a head-to-head comparison in terms of image quality and diagnostic confidence between an individualized post-trigger delay and a conventional fixed post-trigger delay in bolus tracking abdominal multiphase CT.

Methods and materials: Abdominal multiphase CT was performed in 104 patients with either of the two bolus tracking strategies: an individualized post-trigger delay (group A) and fixed post-trigger delay of 11 s (group B). All CT scan parameters and contrast media protocol parameters were consistent between the two groups. Quantitative parameters (organs and blood vessels enhancement, image noise, signal-to-noise ratios [SNRs] and contrast-to-noise ratios [CNRs]) and qualitative visual parameters (overall image quality and diagnostic confidence) were compared. Quantitative and qualitative image quality for the two groups were compared using the Mann-Whitney U and independent sample t test. Degrees of agreement between two radiologists were evaluated using the Kappa analysis.

Results: In the arterial phase (AP), images of group A provided higher attenuation (P ≤ 0.001). Although SNRs of liver, pancreas and aorta were similar in AP between the two groups, CNRs of liver, pancreas and portal vein in group A were significantly higher than those in group B (all P values ≤ 0.002). The overall subjective image quality and diagnostic confidence between the two groups were similar (P = 0.809; P = 0.768).

Conclusion: Compared to a fixed post-trigger delay using bolus tracking, application of an individualized post-trigger delay can optimize the objective image quality in arterial phase without compromising diagnostic quality in abdominal multiphase CT.

Keywords: Abdomen; Bolus tracking; Computed tomography; Scan timing.