Dual Energy Subtraction utilizes the difference in X-ray absorption levels of bones and soft tissue to generate separate images of soft tissue and bone tissue, in addition to projection radiography images. This separation is achieved by successively applying high and low voltages and then using subsequent separate image processing. This enables the rendering of nodes obscured behind ribs in the soft tissue of the chest area or calcifications in bone structures, which is especially useful for diagnoses in the chest area, such as lung cancer.