A system may include determination of a first scatter kernel based on a first energy, a material-equivalent radiological thickness and a first diameter, wherein the first scatter kernel is not a monotonically decreasing function of radial coordinate, determination of a second scatter kernel based on the first energy, the material-equivalent radiological thickness and a second diameter greater than the first diameter, determination of a third scatter kernel based on the first scatter kernel and the second scatter kernel, wherein the third scatter kernel is a monotonically decreasing function of radial coordinate, and estimation of scatter radiation within the projection image of the object based on the third scatter kernel.