Kotlyarov M, et al. - Specimens of various concentrations of monosodium uric acid (MSU) placed in an epoxy-based phantom and an excised porcine foreleg were prepared in order to produce a method that enabled approximating the mass of MSU in a gouty tophus using phantom measurements and involving tophus density into the calculation of the dual-energy CT tophus volumetry. In the porcine foreleg scans, whilst giving supplementary data on the true uric acid burden, comparison of the approximated MSU masses with the true MSU masses of the syringe contents exhibited comparable performance to sole volume measurement. Moreover, the diagnostic ability of the mass approximation technique was validated by retrospective analysis of people with proven gouty arthritis. Hence, for MSU concentrations above 40%, for predicting the uric acid burden in milligrams (instead of ml) in a phantom setting, a method to involve tophus density measurement was strongly authenticated.