When is CT Angio (Computed Tomography Angiography) indicated for vascular imaging?

CT Angiography Indications for Vascular Imaging

CT angiography is the first-line imaging modality for suspected vascular injury in trauma, suspected vascular graft infections, peripheral arterial disease requiring revascularization planning, and acute cerebrovascular injury, with sensitivities and specificities exceeding 95% in most clinical scenarios.

Trauma-Related Indications

Limb Trauma

CT angiography should be performed in severe limb trauma when any of the following findings are present: 1

• Externalized bleeding of arterial origin
• Injury site in proximity to a main vascular axis
• Presence of a non-expanding hematoma
• Isolated neurological deficit
• Ankle-brachial index (ABI) less than 0.9

The evidence strongly supports CTA as first-line imaging, with a meta-analysis demonstrating 96.2% sensitivity and 99.2% specificity for detecting vascular injuries in limb trauma across 891 patients. 1 CTA has replaced diagnostic arteriography due to faster acquisition times, lower cost, and integration into whole-body trauma protocols. 1 Conventional arteriography remains second-line only when CTA is non-contributory due to metal artifact. 1

Head and Neck Trauma

CTA of the head and neck is the standard initial imaging for suspected blunt cerebrovascular injury (BCVI), with sensitivity up to 100% and specificity of 100% when compared to catheter angiography. 1

Specific indications include: 1

• Skull base fractures involving the carotid canal
• Abnormal enlargement of superior ophthalmic vein or cavernous sinus
• Complex skull fractures or scalp degloving
• High-velocity maxillofacial trauma with clinical suspicion for vascular injury

For penetrating neck trauma, CTA is the first-line imaging after clinical assessment, with sensitivity 90-100% and specificity 98.6-100%. 2 This has replaced conventional angiography as the preferred initial modality. 2

The Biffl grading scale (Grades I-V, from <25% luminal narrowing to transection) guides management, with lower grades typically managed medically and higher grades requiring endovascular or surgical intervention. 1

Vascular Graft Infections

CTA is reasonable as the initial imaging procedure for suspected intra-abdominal vascular graft infection, with sensitivity 85-100% and specificity 85-94%. 1

Key indications: 1

• Suspected intra-abdominal vascular graft infection in the absence of recent manipulations
• Gastrointestinal bleeding with suspected aortoenteric fistula (combined with esophagogastroduodenoscopy)
• Surgical planning for graft resection or revascularization

For intrathoracic vascular graft infections, CTA should be used in combination with echocardiography and clinical findings. 1 When CTA findings are indeterminate, MRI, PET/CT, or indium white blood cell scanning may be considered as second-line options. 1

Peripheral Arterial Disease

CTA is increasingly used for pre-intervention planning in peripheral arterial disease, with multidetector CT enabling rapid scanning of the entire arterial system. 1

Advantages over catheter angiography include: 1

• Volumetric rather than planar imaging
• Lower radiation exposure with comparable or lower iodine loads
• Visualization of collaterals and arteries distal to occlusions
• Detection of soft-tissue pathology and nonvascular findings

Noninvasive hemodynamic tests (ABI, toe-brachial index, segmental pressures) remain prerequisite to CTA, establishing the diagnosis before anatomic imaging. 1 CTA sensitivity and specificity for detecting stenoses >50% diameter are approximately 90% with modern multidetector systems. 1

Cerebrovascular Disease

For acute ischemic stroke evaluation, CTA of the neck combined with CTA of the head provides comprehensive assessment of extracranial thromboembolism sources and is essential for endovascular surgical planning. 2

For transient ischemic attack (TIA), noninvasive imaging of cervical carotid arteries should be performed within 48 hours in candidates for carotid endarterectomy or stenting. 2

For suspected cervical artery dissection, CTA is the preferred initial screening examination with sensitivity and specificity approaching 98%, detecting vessel irregularity, wall thickening/hematoma, pseudoaneurysm, and intimal flap. 2

Vasculitis and Large Vessel Inflammation

For giant cell arteritis (GCA), CTA is a useful but not first-line imaging modality, with sensitivity 67-73% and specificity 85-98%. 3 Ultrasound of temporal and axillary arteries is recommended as first-line imaging. 3

CTA may be particularly valuable when: 3

• Patients present with unspecific symptoms requiring evaluation for alternative diagnoses
• Long-term monitoring of structural damage is needed at sites of preceding vascular inflammation
• FDG-PET is unavailable and MRI is contraindicated

Imaging should ideally be performed before or within 72 hours of initiating glucocorticoid therapy, as treatment rapidly reduces detectability of vascular inflammation. 3

Important Limitations and Caveats

Contraindications and technical limitations include: 2

• Severe renal impairment or contrast allergy (consider MRA as alternative)
• Heavy calcifications may overestimate stenosis severity
• Metallic foreign bodies create streak artifact limiting evaluation
• Radiation exposure considerations in young patients or those requiring repeated imaging

Common pitfalls to avoid: 4

• Do not skip initial plain radiographs in extremity trauma before ordering CTA
• Do not delay CTA if signs of vascular compromise or compartment syndrome are present
• Recognize that spatial resolution remains inferior to catheter angiography for morphological assessment of small vessels (<2mm) 5

Catheter angiography remains reserved for: 1, 2

• Inconclusive CTA findings (e.g., possible arteriovenous fistula)
• When endovascular intervention is being considered
• Artifact-limited CTA examinations