What Does CTA Stand For?
CTA stands for Computed Tomography Angiography, a non-invasive vascular imaging technique that uses CT scanning with intravenous contrast to visualize blood vessels throughout the body. 1
Technical Definition
CTA is defined by three essential elements 1:
- Timing: Thin-section CT acquisition timed to coincide with peak arterial and/or venous enhancement 1
- Reconstructions/Reformats: Volumetric data sets interpreted using primary transverse reconstructions and multiplanar reformations 1
- 3-D Renderings: Three-dimensional rendering is a required element that distinguishes CTA from standard contrast-enhanced CT 1
How CTA Works
CTA uses multidetector CT scanners with helical and multistation axial acquisitions to enable rapid scanning of the entire arterial system. 1 The technique offers volumetric (three-dimensional) imaging rather than planar images, enabling extensive image postprocessing including multiplanar reformatted and maximum-intensity projection images to create detailed arterial road maps 1, 2.
Clinical Applications
CTA is widely used across multiple vascular territories 1:
- Peripheral arterial disease: Sensitivity and specificity of 90-100% for detecting stenoses >50% diameter compared to catheter angiography 1, 2
- Pulmonary embolism: The imaging modality of choice for diagnosing acute PE 1
- Cerebrovascular disease: Sensitivity of 96.5% and specificity of 88% for detecting intracranial aneurysms of all sizes 1
- Mesenteric ischemia: Technique of choice for evaluating suspected mesenteric ischemia 1, 3
- Coronary arteries: Non-invasive alternative to catheter angiography for coronary artery assessment 1, 4
Key Advantages Over Catheter Angiography
CTA has largely replaced diagnostic catheter angiography as the reference standard for imaging the aorta and many other vascular territories. 1, 2 The advantages include 1, 2:
- Less invasive with lower complication rates
- Shows cross-sectional anatomy including nonvascular findings
- Visualizes collaterals and arteries distal to occlusions that may not appear on catheter angiography
- More rapid acquisition than MRA
- Better safety in patients with pacemakers or defibrillators
- Less problematic for claustrophobic patients
Important Limitations
Heavily calcified atheromatous disease can significantly limit the ability to interpret CTA images, particularly in tibial arteries. 1, 2 Other limitations include 1, 2, 5:
- Patients over 80 years of age, diabetics, and those on dialysis may have nondiagnostic tibial artery studies 1
- Streak artifacts from metallic stents or coils can obscure vessel assessment 1, 5
- Requires iodinated contrast with associated nephrotoxicity and anaphylactoid reaction risks 1
- Radiation exposure, particularly concerning in pediatric populations 1
- Sensitivity decreases for very small aneurysms (<3mm) or those adjacent to bone 5
Technical Optimization
Dual-energy CTA can reduce blooming and beam-hardening artifacts created by heavily calcified disease and metallic stents when available. 1, 2