How to design injection protocols for multiple detector-row CT angiography (MDCTA)

Abstract

The basis of the development of optimal injection protocols for multiple detector-row CT-angiography is knowledge of the physiological and pharmacokinetic principles of arterial enhancement. This article reviews the key rules of early arterial contrast medium dynamics: (1) Arterial enhancement is directly proportional to the iodine administration rate (iodine flux), and can be controlled by the injection flow rate and the iodine concentration of the contrast medium; (2) Arterial enhancement continuously increases over time with longer injection durations, due to the cumulative effects of bolus broadening and recirculation; (3) The strength of an individual’s enhancement response to intravenously administered CM depends primarily on the patient’s cardiac output and correlates inversely with body weight.

In CTA, any of the following strategies can be employed alone, or in combination, to achieve adequate arterial enhancement in spite of short acquisition times: Increasing the injection rate, using higher concentration CM or increasing the injection duration (and scanning delay) relative to the scan time. Both injection volumes and flow rates should be adjusted to body weight, at least for patients ≤60 kg and ≥90kg BW.

Rationally designed injection protocols based on physiological concepts allow optimal CM utilisation and take full advantage of the technical capabilities offered by modern MDCT scanners.