Disclosed herein is a method, comprising: causing emission of characteristic X-rays of a chemical element in an object by directing radiation to the object; capturing images of the object using the radiation that has transmitted through the object; capturing images of the chemical element in the object using the characteristic X-rays; reconstructing a three-dimensional image of the object based on the images of the object; determining a three-dimensional distribution of the chemical element in the object based on the images of the chemical element; and superposing the three-dimensional image of the object and the three-dimensional distribution of the chemical element in the object to form a superposed image of the object. The radiation directed to the object comes from multiple radiation sources. The images are captured with multiple image sensors. The radiation sources and the image sensors are stationary with respect to the object.