Photon-counting CT made nearly every coronary stent assessable

Design

Retrospective single-centre diagnostic accuracy study with conventional CT comparison group

Population

70 patients with 176 stents on photon-counting CT; 71 patients with 126 stents on conventional CT

Primary outcome

In-stent restenosis ≥50% vs invasive angiography; image quality

Effect

Nondiagnostic 1.1% vs 46.8%; per-stent sensitivity 100%, specificity 86.5%, PPV 56.3%

This single-centre retrospective study, published in European Radiology on 19 September, examined 176 coronary stents in 70 patients scanned with photon-counting CT and compared image quality with 126 stents in 71 patients scanned on conventional energy-integrating CT. Invasive angiography was the reference for in-stent restenosis of 50% or more.

With photon-counting CT, 1.1% of stents were nondiagnostic against 46.8% with conventional CT, and 70.5% had excellent image quality against 23%. For restenosis, per-patient sensitivity and negative predictive value were both 100%, with specificity 85.7%. Per stent, positive predictive value was 56%, so more than four in ten positive calls were false.

Stents have been the classic reason to send a patient straight to invasive angiography. With photon-counting CT, a negative scan may reliably exclude significant restenosis, while a positive one still needs confirmation. The numbers are small, and photon-counting scanners are not yet widely available in India.

• On photon-counting CT, a clearly patent stent makes significant restenosis unlikely in this series.
• Treat a positive stent finding as needing invasive confirmation; more than four in ten were false positives.
• On conventional CT, expect many stents to be nondiagnostic; say so in the report.
• Report the stent diameter; smaller stents are harder to assess on any CT.

Why it matters

Stents may no longer be an automatic reason to skip CT and go straight to the catheter lab.

Don't overread it

Sensitivity of 100% rests on few restenoses; the lower confidence bound was 65%.

The statistics, in plain English

A sensitivity of 100% with a 95% confidence interval from about 65% to 100% means the true value could be much lower; there were few restenoses to find. The high negative predictive value is the more robust finding.

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