First and second year — the floor first, then every step
Confirm the study is diagnostic, map the coronary anatomy and dominance, grade every stenosis in the segment model, then summarise with CAD-RADS 2.0 — stenosis category plus plaque burden and modifiers.
Orient first
The 18-segment SCCT model divides the coronary tree; each stenosis is reported by segment.
Motion (heart rate), calcium blooming and poor opacification are the three reasons a segment becomes non-diagnostic — say which segments and why.
CAD-RADS 2.0 grades the WORST stenosis (0–5) and adds plaque burden (P1–P4) and modifiers (N non-diagnostic, S stent, G graft, HRP high-risk plaque, E exceptions, I ischaemia).
Acquire the study
ECG-gated CT (prospective triggering at a controlled heart rate, commonly under about 65 bpm after beta-blockade) with sublingual nitrate; calcium score on the non-contrast scan.
Read axial source images, curved planar reformats along each vessel and cross-sectional views at each lesion; use the best-quality phase.
Anatomy: left main, LAD, circumflex, RCA; dominance; anomalous origins and interarterial courses.
Each segment on curved reformat and cross-section: plaque type (calcified, non-calcified, partially calcified) and stenosis as a diameter reduction band (minimal, mild, moderate, severe, occlusion).
High-risk plaque features: positive remodelling, low-attenuation plaque, spotty calcification, napkin-ring sign — two or more make HRP.
Plaque burden: from the calcium score or a visual estimate (P1–P4).
Extracardiac structures in the field of view: lungs, mediastinum, aorta, pericardium.
What confirms it
The CAD-RADS category is the worst diagnostic stenosis, with modifiers for anything non-diagnostic, stented, grafted or high-risk.
What licenses you to exclude it
A good-quality CTA with no plaque (CAD-RADS 0) excludes obstructive coronary disease with a high negative predictive value; a non-diagnostic segment does not — label it N.
The classic misread
Over-grading a heavily calcified segment through blooming artefact — narrow the window or use the cross-section.
Calling motion artefact a stenosis — check the other phase.
Missing a malignant interarterial course of an anomalous coronary artery.
Reference values
Each value carries the caveat that keeps it from being misused. Normal limits and diagnostic criteria are kept apart on purpose: a disease cut-off read as a normal range is the more dangerous mistake.
zero is normal; 1–99 is mild, 100–399 moderate, and 400 or more severe by the conventional Agatston bands
Requires the dedicated non-contrast, ECG-gated acquisition — a score eyeballed from a routine chest CT is an estimate and should be labelled as such (ordinal visual scoring is the accepted fallback). Percentile-for-age-and-sex conveys more than the raw number in younger patients.
CT
Coronary arteries · CAD-RADS categorisation — how to report it
a named criteria set: stenosis severity bands (minimal under 25%, mild 25–49%, moderate 50–69%, severe 70–99%, occluded) assign categories 0–5 with modifiers
Category follows the HIGHEST-grade stenosis in the coronary tree; modifiers (plaque burden, stents, grafts, high-risk plaque) are part of the system, not optional extras. Read the definitions from the current version. Versioned criterion — verify against the current edition before clinical use.
CT
See it on real cases
Direct links to Radiopaedia — the reference article and worked cases with their images. Each opens on Radiopaedia.