Stone composition characterization with color coding. The commercially-available uric acid vs. non-uric acid differentiation algorithm with blue-red color coding is shown in the left panel (a); red: uric acid, blue: non-uric acid. Using dual-source DECT with additional tin filtration, it was possible to further characterize the same stones into one of five groups (b). These five groups and their representing colors are: Group 1 in red: uric acid, uric acid dihydrate and ammonium acid urate, Group 2 in yellow: cystine; Group 3 in green: struvite; Group 4 in turquoise: calcium oxalate monohydrate, calcium oxalate dihydrate and brushite; Group 5 in purple: hydroxyapatite and carbonate apatite.