1. A method for producing three-dimensional information of an object in medical X-ray imaging in which method the object is X-radiated from at least two different directions and the said X-radiation is detected to form projection data of the object, characterized in that, said projection data is utilized in a regularized reconstruction method based on solving the non-linear evolution equation 
 ∂ t φ( x, t )=− h ( x, t ) A *( A ( f (φ( x, t )))− m )+α P φ( x, t ) to produce three-dimensional information of the object, x representing the coordinates inside the object under imaging, t representing time, φ representing a level set function indicating the boundary of the object, h representing a positive-valued function, m representing projection data, the operator A representing the X-radiation attenuation model, A* representing the backprojection operator, α representing a positive number, P representing high pass filtering, and f representing a cut-off function returning zero for non-positive arguments and positive values for positive arguments.