What is the scanning regimen for an ascending aortic aneurysm using Computed Tomography Angiography (CTA)?

From the Guidelines

For ascending aortic aneurysms, the recommended CTA scanning regimen includes a non-contrast phase followed by arterial phase imaging after intravenous contrast administration, with ECG-gating to minimize cardiac motion artifacts, and multiplanar reconstructions, as outlined in the most recent guidelines 1. The protocol should involve thin-slice (1-3 mm) acquisition, with imaging timed using bolus tracking, and coverage extending from the thoracic inlet to the diaphragm for thoracic aortic aneurysms, with wider coverage if dissection is suspected. Key considerations for the scanning regimen include:

• The use of high-end MSCT scanners (16 detectors or higher) for their higher spatial and temporal resolution compared with lower-end devices 1
• The importance of ECG-gated acquisition protocols in reducing motion artefacts of the aortic root and thoracic aorta 1
• The recommendation for delayed images after stent-graft repair of aortic aneurysms, to detect endoleaks 1
• The potential for simultaneous CT coronary angiography in suitable candidates scanned on 64-detector systems or higher-end devices, to confirm or exclude the presence of significant coronary artery disease before transcatheter or surgical repair 1 Follow-up scans should use consistent protocols to ensure accurate size comparisons, allowing for precise measurement of aneurysm size, growth rate assessment, evaluation of branch vessel involvement, and detection of complications like dissection or rupture. The frequency of scanning may be based on the established relationship between aneurysm size and rupture risk, with larger aneurysms growing faster and having higher rupture rates, although specific scanning frequencies are not detailed in the most recent guidelines 1.

From the Research

Scanning Regimen for Ascending Aortic Aneurysm with CTA

• The scanning regimen for ascending aortic aneurysm with CTA involves the use of low dose radiation and low volume contrast medium techniques to evaluate non-cardiac chest pain 2.
• A protocol using 80 kilovolt (peak) (kV[p]) and 150 effective milliampere-second (eff mA-s) with 40 mL of low osmolar contrast material administered at 3.0 mL/s can be used 2.
• High-pitch dual-source CT angiography can provide motion-artifact-free imaging of the ascending aorta at a low radiation dose compared to conventional protocol 3.
• The use of low tube voltage and low contrast agent concentration can yield good image quality for aortic CT angiography while reducing radiation dose and iodine contrast agent doses 4.
• The diagnostic quality of CTA can be improved by using simultaneous analysis of the coronary artery tree, which is useful in determining the most suitable procedure for each patient 5.
• The location, size, and etiology of an aneurysm all impact the clinical outcomes, and these factors are used to determine the appropriate timing of surgical replacement 6.

Key Considerations

• Image quality and radiation dose are important considerations in the scanning regimen for ascending aortic aneurysm with CTA 3, 4.
• The use of low dose radiation and low volume contrast medium techniques can reduce the risk of contrast-induced nephropathy 2.
• High-pitch dual-source CT angiography can provide better image quality of the ascending aorta compared to conventional protocol 3.
• The "double-low" technique for aortic CTA can significantly reduce the doses of radiation and iodine contrast agent while maintaining good image quality 4.