Fig. 2

a Axial CT image showing right L4/5 facet joint erosion (white arrow) with calcified peri-articular mass encroaching on lumbar canal (dashed white arrow), and b corresponding DECT image (Siemens Somatom Force™) showing monosodium uric acid crystal deposition (green). c Sagittal T2–fat suppressed MRI image (General Electric 1.5 T Signa Excite™) of the lumbar spine showing the soft tissue mass seen in a and b causing marked lumbar canal stenosis, and d corresponding DECT image (Siemens Somatom Force™) showing attenuation consistent with monosodium uric acid crystal deposition