Utilisation of Objective and Subjective Image Quality Metrics to Guide Optimal Contrast Volumes for Abdominal CT

Determining the appropriate volume of iodinated contrast media (ICM) for portal venous phase abdominal computed tomography (CT) remains challenging. Evidence is limited regarding the volume required for consistent enhancement and whether this translates into optimal subjective image quality. To address this gap, we compared fixed-volume and weight-based dosing strategies, utilising objective enhancement and subjective image quality to identify approaches that may optimise diagnostic performance.

The abdominal CT ICM dosing protocol was revised from fixed (100 mL) to weight-based (1 mL/kg, 10 kg increments) volume dosing. Data from 90 fixed and 90 weight-based ICM volume procedures were matched by age, gender, weight and kVp. Objective measures of ICM enhancement (Hounsfield unit, HU) were obtained in key vessels and organs. Subjective image quality scores were obtained from 24 cases per group, matched by weight and kVp, followed by visual grading characteristic (VGC) analysis.

Weight-based dosing reduced the dependence of key vessel and organ enhancement on patient size compared with fixed dosing. VGC analysis comparing patients < 90 kg and ≥ 90 kg suggests light patients require greater HU enhancement than heavy patients to achieve equal subjective image quality.

Consistent HU enhancement across all patient sizes can be achieved by using weight-based ICM volume dosing in abdominal CT, although this does not necessarily translate to consistent subjective image quality. Our findings suggest that lighter patients may benefit from greater enhancement to achieve equivalent subjective image quality to larger patients, highlighting the need for further optimisation of ICM dose strategies beyond standard weight-based approaches.