CIMT & Plaque Imaging
Ultrasound the arteries
Carotid intima-media thickness (CIMT) uses ultrasound to measure the thickness of the inner two layers of your carotid arteries — and spot soft plaque before it calcifies. Unlike CAC it picks up non-calcified lesions, which matters in younger people whose plaque hasn't hardened yet.
Better for younger adults
In people under 50, CAC scores are often 0 even when soft plaque is present — calcification hasn't started yet. CIMT catches this earlier phase. Once plaque calcifies CAC is more specific, but CIMT keeps its edge for tracking disease progression over time.
Not perfect, still useful
CIMT has operator-dependent quality variability — two technicians can produce different results on the same person. It's also less standardised than CAC. In 2013 the ACC/AHA stopped recommending it for population screening. Preventive cardiologists still use it in targeted cases, especially repeat measurements on the same person, same machine, same reader.
When to pick CIMT over CAC
Under 45 with family history of early CVD and normal labs. CAC will likely be 0, so you learn nothing. CIMT can reveal early thickening and soft plaque. Over 50, CAC is almost always the better first choice. Many preventive cardiologists use both, sequenced.
What the numbers actually mean
Mean CIMT < 0.6 mm is normal for under-40s. 0.6–0.8 mm is mild thickening (vascular age 5–10 years older than chronological). 0.8–1.0 mm is moderate thickening (vascular age +10–15 years). > 1.0 mm or any focal plaque > 1.5 mm is plaque territory and should trigger aggressive lipid + BP management. Bots 2012 showed each 0.1 mm increase associates with ~10–15 % higher CV event risk over 5 years.
Key Takeaway
CIMT shines when CAC is likely to miss — younger adults with family history, progression tracking over years. It has quality issues, but used well it closes the gap that CAC leaves below age 50. Track the same artery on the same machine annually for the most reliable trend.