A prospective study of 126 women with BI-RADS 4C or higher lesions compared photon-counting CT against MRI, full-field digital mammography and, in a subset with locally advanced disease, FDG PET/CT. Four radiologists read independently.
Agreement between photon-counting CT and MRI was good to excellent for lesion characterisation and clinical T category, and agreement with pathological size was the highest of the modalities compared. For 46 pathologically confirmed additional lesions, photon-counting CT was 44 percentage points more sensitive than mammography and statistically indistinguishable from MRI.
And then the finding that keeps it from being a replacement: 44% of microcalcifications seen on mammography were missed on photon-counting CT. In a disease where microcalcification is often the only sign of ductal carcinoma in situ, that is not a rounding error.
So this is a feasibility study reporting a genuinely promising result and a genuinely disqualifying one in the same breath. Photon-counting CT looks capable of doing much of what breast MRI does for staging. It cannot do what mammography does for calcification, and any pathway built on it would need mammography retained rather than replaced.
- Treat this as feasibility, not as a pathway change: 126 participants over three months at one centre.
- The microcalcification gap is the limiting finding — 44% missed against mammography.
- Where it looks strongest is T categorisation and agreement with pathological size.
- Any future protocol would need mammography retained alongside, not replaced.
- Watch for radiation dose comparisons, which this study does not resolve.
The statistics, in plain English
Kappa and the intraclass correlation coefficient both measure agreement rather than accuracy, and the distinction matters: two readers can agree perfectly and both be wrong. Kappa values of 0.86 to 0.88 for T categorisation are high agreement; an ICC of 0.70 to 0.81 against pathological size is good but not excellent. The sensitivity difference against mammography, 44 percentage points with an interval of 19 to 66, is wide because only 46 confirmed additional lesions were available — a real effect, imprecisely measured. The microcalcification figure of 44% missed carries an interval of 27 to 52, so somewhere between a quarter and half. With 126 participants recruited over three months at one centre, every one of these numbers should be read as a first estimate.
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