Photon-Counting–Detector CT Can Characterize Small Renal Stones

Use of a photon-counting-detector CT for renal stones is similar to using dual-energy CT.

Photon-counting–detector (PCD) CT is superior to standard CT in helping characterize small renal stones, according to a study published in the journal Radiology.

Researchers from the United States and Germany sought to evaluate the utility and efficacy of a PCD CT system in improving the automatic characterization of stones of 3 mm or smaller.

Ten women and 20 men, median age 61 years, participated in the study. All underwent a clinical renal stone characterization scan with dual-energy CT, followed by a research PCD CT scan with the same radiation dose. Two radiologists reviewed for stones, which were identified as uric acid or non–uric acid. Stone size and contrast-to-noise ratio were calculated.

The results showed 160 renal stones; 91 were 3 mm or smaller in axial length. The odds of detecting a stone at PCD CT were 1.29 for all stones, compared with 1-mm-thick routine images from dual-energy CT.

Stone segmentation and characterization were successful at PCD CT in 70.0% (112 of 160) of stones versus 54.4% (87 of 160) at dual-energy CT, and was superior for stones 3 mm or smaller at PCD CT (45 versus 25 stones, respectively). Stone characterization agreement between scanners for stones of all sizes was substantial.

The researchers concluded that using a PCD CT to detect renal stones was similar to using dual-energy CT, however the PCD CT was better able to help characterize small renal stones.