Image Quality Monitoring: Variability in Contrast Enhancement Across a Clinical Population

Purpose: Iodinated contrast agents are commonly used in computed tomography (CT) to delineate vasculature and blood perfusion by enhancement of Hounsfield unit values. Contrast-enhancement is affected by anatomical and physiological factors, and varies across patients. The purpose of this study was to quantify the variability of the contrast-enhancement amongst patients within a clinical operation and investigate trends of this enhancement as a function of patient size and age. Methods: Using an IRB-approved protocol, an algorithm was developed and applied to automatically assess Hounsfield unit (HU) value enhancement from the aorta of 600 patients (200 contrast enhanced with 150 mL of Isovue-300 contrast medium, 400 non-contrast enhanced, 400 chest and 200 abdominal/pelvic). The results were analyzed in terms of the standard deviation of the mean aortic HU values across the population (for both contrast-enhanced and non-contrast enhanced cohorts) and the relationships between mean aortic HU values and patient factors (size and age). Results: The HU values of the aorta exhibited a seven-fold enhancement in magnitude in contrast-enhanced exams, as expected. More remarkably, they also exhibited five times more variability in the aortic HU values compared to non-contrast-enhanced cohort (25.1 11.0 for non-contrast and 177.2 60.0 for contrast-enhanced scans). There was no statistically significant trend between aortic HU values and age with either exam type (p > 0.2). The mean HU values in contrast-enhanced exams, however, showed a decreasing trend with patient size in (p < 0.05). Conclusion: Mean HU values of the aorta were found to be more variable in contrast enhanced examinations. Size also exhibits a strong influence. Considering that the applied protocol used a fixed amount of administrated contrast agent irrespective of patient size, this presents a potential to right-size the amount of administered contrast as a function of patient size.

Duke Scholars

Author Ehsan Abadi Radiology

Author Aiping Ding Radiology

Author Ehsan Samei Radiology