From the Guidelines
For planning abdominal aortic aneurysm (AAA) surgery, a contrast-enhanced CT angiogram with thin-slice acquisition (1-2 mm) is best, as recommended by the most recent guidelines 1. This should be performed as a multiphasic study with arterial and venous phases to provide optimal visualization of the aorta and its branches. The protocol should include coverage from the thoracic aorta to the femoral arteries to allow complete assessment of access routes and landing zones for potential endovascular repair. Intravenous contrast (typically 100-150 mL of iodinated contrast at 4-5 mL/second) is essential for vessel opacification. The arterial phase should be timed using bolus tracking with a region of interest placed in the descending thoracic aorta and a trigger threshold of 100-150 Hounsfield units. Three-dimensional reconstructions, including multiplanar reformats (MPR), maximum intensity projections (MIP), and volume rendering techniques (VRT), are crucial for accurate measurement of aneurysm dimensions, neck angulation, and relationship to branch vessels. This comprehensive imaging approach allows surgeons to determine whether open surgical repair or endovascular aneurysm repair (EVAR) is more appropriate and helps with detailed procedural planning, including selection of appropriate stent graft sizes and configurations, as supported by recent studies 1.
Some key points to consider when planning AAA surgery include:
- The use of CT angiography as the primary imaging modality for preoperative planning and follow-up after repair 1
- The importance of accurate measurement of aneurysm dimensions and neck angulation for procedural planning 1
- The role of three-dimensional reconstructions in evaluating the relationship between the aneurysm and branch vessels 1
- The consideration of patient factors, such as renal function and allergy to iodinated contrast, when selecting an imaging modality 1
Overall, the use of a contrast-enhanced CT angiogram with thin-slice acquisition and multiphasic study is the best approach for planning AAA surgery, as it provides the most accurate and comprehensive information for procedural planning and helps to minimize adverse outcomes 1.
From the Research
CT-Angiogram Types for Abdominal Aortic Aneurysm Surgery Planning
The type of CT-angiogram best suited for planning abdominal aortic aneurysm surgery can vary based on patient-specific factors such as renal function and the need for contrast enhancement.
- Contrast-Enhanced CT Angiography: This is currently considered the gold standard for preoperative imaging and image-based treatment planning in AAA repair 2. It provides detailed images of the aorta and its branches, which are crucial for planning endovascular aneurysm repair (EVAR).
- Low-Volume Contrast CT Angiography: For patients with impaired renal function, a technique using direct intra-aortic injection of a low volume of iodinated contrast can provide adequate and reproducible aortic enhancement on CT angiography, limiting the total volume of contrast required 3.
- Non-Contrast MR Angiography: This can be an alternative for patients with contraindications to CT, such as renal impairment. It allows for accurate monitoring of aortic diameters and can provide preoperative anatomic information equivalent to contrast-enhanced CT for surgical planning 4, 5.
Considerations for Choosing a CT-Angiogram Type
When selecting a CT-angiogram type for abdominal aortic aneurysm surgery planning, considerations include:
- Patient renal function: Patients with impaired renal function may benefit from low-volume contrast CT angiography or non-contrast MR angiography.
- Need for detailed aortic and branch vessel imaging: Contrast-enhanced CT angiography is preferred for its high-resolution images.
- Presence of contraindications to CT: Non-contrast MR angiography can serve as an alternative in such cases.
Imaging Techniques and Their Applications
Different imaging techniques have their applications: