A method, comprising: decomposing obtained first spectral image data, which includes at least a first component corresponding to a targeted first K-edge based contrast agent administered to a subject if a target of the targeted first K-edge based contrast agent is present in the subject, into at least the first component; reconstructing the first component thereby generating a first image of the targeted first K-edge contrast agent; determining if the targeted first K-edge contrast agent is present in the first image; and generating a signal indicating the targeted first K-edge contrast agent is present in the first image in response to determining the targeted first K-edge contrast agent is present in the first image; characterized by i) decomposing second image data, which are spectral image data and includes a second component corresponding to a second K-edge contrast agent administered to the subject and which are obtained in response to generating a signal indicating the targeted first K-edge contrast agent is present in the first image, into at least the second component and reconstructing the second component thereby generating a second image of the second contrast agent, wherein the first spectral image data and the second spectral image data are respectively from first and second different spectral scans of the subject or ii) reconstructing second image data, which are non-spectral image data and includes a second component corresponding to a second non-spectral based contrast agent administered to the subject and which are obtained in response to generating a signal indicating the targeted first K-edge contrast agent is present in the first image, thereby generating a second image of the second contrast agent; reconstructing the first spectral image data thereby generating a reference image without the second contrast agent; and generating a contrast image based on a difference between the second image and the reference image. decomposing obtained first spectral image data, which includes at least a first component corresponding to a targeted first K-edge based contrast agent administered to a subject if a target of the targeted first K-edge based contrast agent is present in the subject, into at least the first component; reconstructing the first component thereby generating a first image of the targeted first K-edge contrast agent; determining if the targeted first K-edge contrast agent is present in the first image; and generating a signal indicating the targeted first K-edge contrast agent is present in the first image in response to determining the targeted first K-edge contrast agent is present in the first image; characterized by i) decomposing second image data, which are spectral image data and includes a second component corresponding to a second K-edge contrast agent administered to the subject and which are obtained in response to generating a signal indicating the targeted first K-edge contrast agent is present in the first image, into at least the second component and reconstructing the second component thereby generating a second image of the second contrast agent, wherein the first spectral image data and the second spectral image data are respectively from first and second different spectral scans of the subject or ii) reconstructing second image data, which are non-spectral image data and includes a second component corresponding to a second non-spectral based contrast agent administered to the subject and which are obtained in response to generating a signal indicating the targeted first K-edge contrast agent is present in the first image, thereby generating a second image of the second contrast agent; reconstructing the first spectral image data thereby generating a reference image without the second contrast agent; and generating a contrast image based on a difference between the second image and the reference image. i) decomposing second image data, which are spectral image data and includes a second component corresponding to a second K-edge contrast agent administered to the subject and which are obtained in response to generating a signal indicating the targeted first K-edge contrast agent is present in the first image, into at least the second component and reconstructing the second component thereby generating a second image of the second contrast agent, wherein the first spectral image data and the second spectral image data are respectively from first and second different spectral scans of the subject or ii) reconstructing second image data, which are non-spectral image data and includes a second component corresponding to a second non-spectral based contrast agent administered to the subject and which are obtained in response to generating a signal indicating the targeted first K-edge contrast agent is present in the first image, thereby generating a second image of the second contrast agent; reconstructing the first spectral image data thereby generating a reference image without the second contrast agent; and generating a contrast image based on a difference between the second image and the reference image.