Fig. 5

DECT images showing examples of colour-coded DECT lesions in knee joints. a–c Dual-energy CT (DECT) scans of the left knee joints in three different patients showing colour-coded DECT lesions with similar appearances and locations. Analysis of the DECT ratios revealed that a is dominated by definite MSU depositions, while b and c are dominated by likely calcium-containing depositions. a Definite MSU depositions in a gout patient. A 54-year-old gout patient with no comorbidities. DECT revealed 58 colour-coded DECT lesions characterized by a low mean DECT ratio (1.01, SD 0.09) consistent with the lesions representing pure MSU depositions. b Calcium-containing depositions in a gout patient. A 67-year-old gout patient with comorbidities in the form of obesity and knee osteoarthritis. DECT revealed 39 colour-coded DECT lesions characterized by a high mean DECT ratio (1.22, SD 0.16) consistent with lesions representing calcified tissues (possibly calcifications in the menisci/cartilage and/or calcified MSU depositions). c Calcium-containing depositions in a non-gout patient. A 56-year-old non-gout patient with comorbidities in the form of obesity and myocardial disease. The plasma urate level was 0.29 mmol/L (4.9 mg/dL), and joint puncture showed an absence of MSU crystals but a presence of multiple calcium pyrophosphate (CPP) crystals. DECT revealed 57 colour-coded DECT lesions characterized by a high mean DECT ratio (1.24, SD 0.17) consistent with lesions representing calcified tissues (possibly calcifications in the menisci/cartilage and/or CPP crystal depositions)