A method of generating a modified X-ray image includes obtaining an X-ray image, obtaining a CT image corresponding to the X-ray image, determining a mapping between the X-ray image and the CT image, identifying a structure of interest in the CT image, generating an attenuation map from the CT image, the attenuation map indicative of attenuation due to the structure of interest or everything but the structure of interest on the X-ray image, and generating the modified X-ray image by subtracting the attenuation map from the X-ray image.