The following question has been sent by Luke Riverstone, Radiographer, Qscan Radiology Clinics, Australia:

We have recently obtained a Siemens DSCT.  We performed our first DE KUB the other day and the Dual Energy Software indicated that there was 1 Kidney stone that was of a Uric Acid composition and 1 was of Calcuim composition.

The Radiologist at our institution wanted to know why he should trust the software to determine the compostion of the Stone.  He indicated that he would not be mentioning it in his report or to the urologist until he had seen some data on it first.

My Question is: is there any published data on the accuracy of the DE scan in determining the compostion of the Kidney Stones.  If not what information can I pass on that will give the confidence in to report based on the finding of the DE scan?

Hatem Alkadhi, M.D., University Hospital Zurich:

Until now, there are two published papers dealing with the topic urinary stone-characterization with dual energy CT. One is an ex-vivo study from Primak et al.: Noninvasive differentiation of uric acid versus non-uric acid kidney stones using dual-energy CT. Acad Radiol. 2007;14:1441-7.
The other study is an ex-vivo and in-vivo study from Graser et al.: Dual energy CT characterization of urinary calculi: initial in vitro and clinical experience. Invest Radiol. 2008;43:112-9.
Both studies could convinsingly demonstrate that dual-energy CT allows to discriminate uric acid stones from other stone types with a high accuracy. Thus, I would be confident in reporting a stone to contain uric acid or not.
Certainly, future in-vivo studies including large patient populations are required to confirm these first experience studies and to assess the true diagnostic performance of dual-energy CT for the differentiation of uric-acid versus non-uric-acid containing stones in comparison with chemical analysis.

Best regards,
Hatem Alkadhi

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