RADS - Reporting and Data Systems Support

FAQ-143: How does CEUS LI-RADS differ from CT/MR LI-RADS?

Key differences between CEUS and CT/MRI LI-RADS are summarized below: 

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FAQ-144: Why does intrahepatic cholangiocarcinoma (ICC) show early marked washout on CEUS but delayed central enhancement on CT/MRI?

CEUS microbubbles are too large to pass through vascular endothelial fenestrations. Instead, they remain confined to the blood space or bool pool (hence, “blood space agents” or “blood pool agents”) and their postarterial phase distribution reflects regional blood volume. Since ICCs have low blood volume, they show early and marked postarterial phase washout after administration of these agents – earlier and more marked, in fact, than most HCCs. By comparison, the low-molecular-weight (LMW) agents used in CT and MRI pass through endothelial fenestrations easily, extravasate into the interstitium, and accumulate progressively in the centrally located fibrous stroma of these tumors. This produces the characteristic delayed central enhancement of ICCs at CT or MRI. 

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FAQ-145: Why do HCCs typically show washout on CEUS and on CT/MRI?

Washout is a poorly understood phenomenon. A partial explanation: since most HCCs have lower blood volume and lower extracellular volume than liver, they generally exhibit washout with blood-pool agents and with LMW extracellular space agents.

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FAQ-146: Why is LR-M termed “probably or definitely malignant”? 

Since rare benign entities (e.g., inflammatory pseudotumor, sclerosed hemangioma, abscess) may show LR-M features (e.g., rim APHE) on all dynamic imaging modalities (CEUS, CT, MR), “probably or definitely malignant” is more appropriate than “definitely malignant.” 

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FAQ-147: Is there a size threshold for CEUS LR-M?

No. Although CEUS is usually performed to assess nodules ≥ 10 mm detected on surveillance US, smaller nodules with CEUS LR-M features may be identified during CEUS and should be categorized LR-M.

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FAQ-148: Why are arterioportal shunts (APS) not visible on CEUS?

One plausible explanation is that the microscopic shunts are too small to be depicted by CEUS, whereas CT and MRI detect the extravasation of contrast material into the regional interstitium. Regardless of the mechanism, the insensitivity of CEUS to perfusion alterations is an advantage because these can cause diagnostic confusion. 

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FAQ-149: Why do the tie-breaking rules choose lower certainty? 

See CT/MRI LI-RADS Core

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