A method is presented for generating a 3D image of an object using x-rays. The invention describes a method of generating an image of a slice through the object using a large number of detector elements as employed in commonly used x-ray scanners. The method described is a two step process, in the first step, Algebraic methods are used to solve a set of simultaneous linear equations to solve for the densities of the pixels representing the slice. The dimension of these pixels defining the slice is large in comparison to the size of detector elements, therefore a second step of backprojection is used to generated a slice image of higher resolution. The use of a second or a third source further allows the generation of higher resolution images.