Weight-based contrast in abdominal CT

Intravenous iodinated contrast is commonly and routinely used in abdominal imaging computed tomography (CT) to demonstrate patient’s anatomy and visualise and pathology.

Historically, a fixed volume of contrast is used for abdominal CT. However, this fixed dose approach means small patients are typically overdosed, resulting in excessive enhancement of the abdominal organs. Conversely, larger patients are underdosed which results in scans that have less than ideal enhancement. The idea of a simple weight-based contrast regimen was proposed by our team as a solution to this problem.

A review of other Queensland Health sites indicated that most medical imaging departments were using fixed volume or simplified 2- or 3-step volume protocols (e.g., small, medium, and large patients). A thorough literature review was conducted to see if there was evidence to support a more tailored approach. The literature suggested that a weight-adjusted contrast dosing protocol can objectively provide more consistent vessel and solid organ enhancement and subjectively improve image quality across a spectrum of body weights. In addition, it could reduce the amount of total contrast used, saving money and reducing waste.

The issue with the current body of literature is that there is no consensus as to the ideal enhancement of the image, in other words how the image should look. It is largely dependent on the country of the study and the patient demographics of that region. As a result of this, our team decided to conduct our own study to determine if the patient specific approach could work at our site.

Our team consisted of radiographers, radiation physicists and radiologists. A weight-based contrast protocol was established by our team based on 1ml of contrast per kilogram of patient weight in 10kg increments and was rolled out across the department. Quantitative and qualitative data was collected to compare the fixed dose vs weight-based methods and analysed.

The main aim of this clinical audit was to determine whether a weight-based contrast regimen in abdominal CT can provide more consistently enhanced images for our clinicians across the spectrum of patient sizes. In addition, can the change in practice reduce contrast wastage and therefore costs. If so, the weight-based protocol could be implemented across more Queensland health sites to improve the quality of the abdominal CT scans we perform statewide.