What Photon-Counting CT Reveals About Carotid Perivascular Adipose Tissue

We’re finally seeing something we couldn’t see before, and it’s subtle.

This is a project that Erica Maffei, MD, Luca Saba, MD, and I originated some time ago in a totally explorative manner and now the first results of its feasibility are out in a new study recently published in European Radiology.¹

Photon-counting CT (PCCT) is starting to reveal a new layer of vascular biology: the behavior of perivascular adipose tissue (PVAT).
In this study, PCCT was used to analyze PVAT around the carotid artery millimeter by millimeter. Not globally, not averaged, but layer-by-layer.

What did we see? There was a clear, consistent pattern: the closer you get to the vessel wall, the higher the attenuation. The farther away, the lower it goes.

This isn’t just imaging. This is a spatial gradient of biology.

Perivascular adipose tissue is not “just fat.” It’s metabolically active.
It reacts to what happens in the vessel wall. It may reflect local inflammation.

Now, for the first time, we can map it with precision.

Here is where it gets interesting. The patterns are not the same in everyone. Some patients show smooth gradients. Others may have irregular gradients or even inverted gradients.

That variability is the real signal. It tells us that vascular disease is not binary. It’s not “stenosis vs. no stenosis” nor even “inflammation vs. no inflammation.” It’s complex, individual, spatially heterogeneous biology.
Photon-counting CT is finally giving us the resolution to see it.

Are we ready to use PVAT clinically? Not yet. But are we opening a new window into early disease?

Absolutely.

The future is not about seeing the lumen better. It’s about understanding the environment around it, and this … is just the beginning.

Dr. Cademartiri is the director of advanced cardiovascular imaging and photon-counting CT at the Scientific Institute for Research, Hospitalization, and Healthcare Synlab Diagnostic Network in Naples, Italy. He is also a consultant in advanced cardiovascular imaging at CDI/Centro Diagnostico Italiano in Milan, Italy.

Reference

1. Saba L, Alkadhi H, Maffei E, et al. Photon-counting CT characterization of carotid perivascular adipose tissue: a layer-by-layer quantitative analysis. A preliminary analysis in an asymptomatic population. Eur Radiol. 2026 Apr 7. doi: 10.1007/s00330-026-12481-z. Online ahead of print.

(Editor’s note: This blog was adapted with permission from Dr. Cademartiri’s original LinkedIn post at https://www.linkedin.com/feed/update/urn:li:activity:7447512518513688576/?originTrackingId=xEYrqSb06Hm06%2BO1oOZSFQ%3D%3D .)