CT Angiography (Aorta, Carotid, Run-off)

What it does

CT Angiography reads arterial CTA outside the heart and the brain: the thoracic and abdominal aorta, the carotid bifurcations and the lower-limb run-off. Upload the arterial series, with a non-contrast or delayed series when the protocol includes one; the run segments the aorta and its branches, builds a centreline and measures diameters orthogonal to it at the standard landmarks.

On that vessel model it checks for acute aortic syndrome (dissection and intramural haematoma), sizes aneurysms and tracks their growth against a prior and grades carotid stenosis by the NASCET method. After endovascular repair it detects endoleaks and gives their type; on a run-off CTA it maps stenoses and occlusions from the aorto-iliac segment down to the pedal arteries.

Intended use

Decision support for whoever must act on an arterial CTA: the emergency physician with chest or back pain on a non-gated study, the vascular surgeon following an aneurysm or an endograft, the stroke team reading the neck vessels. Diameters follow one method at fixed landmarks, so serial studies can be compared.

Who it is for

Vascular and emergency radiologists, vascular and cardiothoracic surgeons, interventional radiologists, stroke neurologists and angiologists. Developers add aortic measurements and dissection triage to a PACS, aneurysm surveillance programme or vascular registry.

Accepted input

• Territories (DICOM CT series): aortic CTA (thoracic, abdominal or both), carotid CTA of the neck, lower-limb run-off CTA.
• Additional phases: a non-contrast series and a delayed series of the same examination, when acquired.
• Prior CT or CTA in prior_files: aneurysm growth and sac change after repair are measured against it.

Requirements

Requirement	Why
Arterial-phase contrast	Lumen, flap and stenosis are read on opacified vessels; a mistimed bolus is flagged
Non-contrast series when acute aortic syndrome is suspected	Intramural haematoma is best seen without contrast
Arterial and delayed series after EVAR	Endoleak typing needs both phases
Continuous coverage of the territory	Diameters and branch involvement need the whole segment
Rescale Slope and Intercept	Calcium, thrombus and contrast are separated in Hounsfield units

Aneurysm diameters are also measured on non-contrast CT. Aortic-root motion, contrast streak and calcium blooming in small vessels are reported as quality flags.

Optional context

Symptoms (acute chest or back pain, claudication, transient ischaemic attack), previous repair or stent graft and the date of the prior study go in clinical_context.

The result

One JSON result in sections; measurements carry the landmark or vessel segment they were taken at.

Section	Content
Aorta and branch segmentation	Multiclass mask of the aorta, branches and aortic zones, with the centreline
Aortic dissection	Dissection or intramural haematoma, entry tear, true and false lumen, branch involvement, malperfusion, Stanford and DeBakey class and zones
Aortic aneurysm	Maximal diameters orthogonal to the centreline at standard landmarks, extent and growth against the prior
Endoleak	Endoleak with its type (I–V), sac diameter and volume change
Carotid stenosis	Bifurcation and ICA segmentation, NASCET-method percentage stenosis, plaque, web and dissection flags
Peripheral run-off	Segmental stenoses and occlusions from the aorto-iliac level to the pedal arteries, calcification burden
Draft report	Opt-in (options.report): an English narrative that interprets the result for the reader (findings, impression, limitations); every number is checked against the findings

Standards

• DICOM: SR TID 3900 CT/MR Cardiovascular Analysis Report with TID 3902 Vascular Analysis for diameters and stenoses; SEG for the aortic tree and lumens; key images, Encapsulated PDF and FHIR DiagnosticReport.
• Guidelines: ESC 2024 aortic guidelines; ESVS 2024 abdominal aortic aneurysm guidelines; SVS/STS 2020 reporting standards for type B aortic dissection.
• Grading: NASCET method for carotid stenosis; Stanford and DeBakey classes for dissection.

Measurement notes

Every diameter is taken in the plane perpendicular to the centreline, not on axial slices, so oblique segments are not overestimated. Growth is the difference between matched landmarks on the current and the prior study.