Image processing apparatus, radiation imaging system, image processing method, and non-transitory computer-readable storage medium

An image processing apparatus comprising:

• a processor;
• and
• a memory, including instructions stored thereon, which when executed by the processor cause the apparatus to:
• perform noise reduction processing and material decomposition processing using a plurality of images corresponding to a plurality of different radiation energies obtained by irradiating an object with radiation and performing imaging;
• generate a noise reduction image by applying filter processing for each frequency component obtained by resolving a thickness image of a material obtained by the material decomposition processing into a plurality of frequencies;
• generate an image by material re-decomposition processing using the thickness image after noise reduction, which is obtained by combining the noise reduction images for each frequency component and an accumulation image obtained based on combining of the plurality of images,
• wherein the filter processing includes spatial filter processing applied for each frequency component and time filter processing applied for each frequency component after the spatial filter processing, and
• wherein the time filter processing is performed for an image generated by subtracting a thickness image with restored frequency component from the noise reduction image to which the spatial filter processing is applied.