Cardiothoracic CT Angiography: Current Contrast Medium Delivery Strategies

Abstract

Thorough understanding of contrast medium dynamics is essential for the design of effective acquisition and injection protocols. This article provides an overview of the fundamentals affecting contrast enhancement, emphasizing the modifications to contrast material delivery protocols required to optimize cardiothoracic CT angiography.

The role of multidetector-row CT in the diagnosis, classification and management of acute aortic syndrome

“…4,31,33 Following the unenhanced study, a bolustracked CT angiogram should be performed using 120 ml of 370 mg l ml 21 iodinated contrast medium delivered at a rate of between 4 and 5 ml s 21 via a power injector to achieve a target opacification of the aorta of .250 HU. 34 The volume of contrast should be reduced to 80-100 ml in elderly patients with reduced cardiac outputs. 34 ECG-gated acquisitions are performed prospectively at mid-diastole with a breath-hold performed whilst scanning the thoracic aorta to the level of the diaphragmatic hiatus, and the patient asked to free breath whilst the subdiaphragmatic aorta is imaged.…”

“…34 The volume of contrast should be reduced to 80-100 ml in elderly patients with reduced cardiac outputs. 34 ECG-gated acquisitions are performed prospectively at mid-diastole with a breath-hold performed whilst scanning the thoracic aorta to the level of the diaphragmatic hiatus, and the patient asked to free breath whilst the subdiaphragmatic aorta is imaged. Unlike coronary CT angiography studies, pre-medication with b-blockers or nitroglycerine is not required and should be avoided.…”

“…In order to further minimize streak artefact arising from the superior vena cava, a saline flush of 20 ml should be power injected immediately following contrast medium injection using the same flow rate. 34 In the evaluation of AAS, craniocaudal coverage should extend from the thoracic inlet to the aortoiliac bifurcation. 3,27 This range of coverage is important to diagnose major branch vessel involvement and to characterize the presence and severity of the resultant organ malperfusion.…”

Clinical Pharmacology, Uses, and Adverse Reactions of Iodinated Contrast Agents: A Primer for the Non-radiologist

“…This opacification is proportional to the iodine delivery rate, which is determined primarily by the rate of contrast injection and is influenced by the concentration of iodine in the contrast medium. 10 Because arterial opacification is the primary goal, the total amount of contrast media used is frequently less of an issue than how quickly the contrast can be injected. Therefore, as with catheter angiography, viscosity and iodine concentration have an effect on the selection of the appropriate contrast media to be injected, particularly when intravenous access is limited.…”

The Significance of Pulmonary Artery Size in Pulmonary Hypertension

“…The conditions that cause mechanical changes to the mediastinal vasculature by compression, traction, or shifting, as well as pathologic changes in the heart or lungs, such as from congenital heart disease, prior surgeries, or radiation, can cause additional anatomic distortion. Despite limited investigations that address this [20,[37][38][39], we suspect that technical issues in the imaging of the PA (e.g., body position, different acquisition protocols and reconstruction algorithms, depth of inspiration, the use of contrast, and reduced intraand inter-rater reliability) may also affect the accurate measure of the PA size and further confound the relationship between the PA size and PA pressures. Although logical deduction would indicate that the PA size should correlate nicely with PH and PH severity, there are a multitude of factors that may potentially make the measurement unreliable or inaccurate.…”