To obtain a fast estimation of the total impurity density distribution in a poloidal cross section from soft X-ray (SXR) measurements during quasi-stationary phases, the possibility that ionization equilibrium may have little influence on the emissivity profile of Ni and Fe in the core region of tokamak plasmas is investigated. Preliminary and encouraging results that support this assumption under certain conditions are found. A simplified approach aimed at computing a satisfactory estimation of the total density of a unique and identified impurity directly from an absolutely calibrated SXR tomographic inversion is implemented. An example of application to a previously and independently performed transport simulation of a Ni injection in Tore Supra is then given.