Information processing apparatus and method, and radiography system

1. An information processing apparatus, comprising:

at least one of (a) one or more processors connected to one or more memories storing a program including instructions executed by the one or more processors and (b) circuitry configured to perform:

obtaining at least three radiation images obtained based on radiation emitted onto an object, each of the at least three radiation images corresponding to each of at least three types of energy; and

calculating, by separating a predetermined substance having a known attenuation coefficient in the object and a remaining substance other than the predetermined substance in the object based on the at least three radiation images, an effective atomic number of the remaining substance.

2. The information processing apparatus according to claim 1 , wherein in the calculating, a thickness or an area density of the predetermined substance, the effective atomic number of the remaining substance, and a thickness or an area density of the remaining substance are calculated using a known attenuation coefficient of the predetermined substance.

3. The information processing apparatus according to claim 1 , wherein in the calculating, a thickness or an area density of the predetermined substance, a thickness or an area density of the remaining substance, and the effective atomic number of the remaining substance are calculated by solving a non-linear simultaneous equation obtained based on the at least three radiation images and equations expressing attenuations of radiation caused by the predetermined substance and the remaining substance corresponding to the at least three types of energy.

4. The information processing apparatus according to claim 3 , wherein the non-linear simultaneous equation is solved through a successive approximation.

5. The information processing apparatus according to claim 3 , wherein the non-linear simultaneous equation is solved with approximating each of the at least three types of energy to monochromatic energy.

6. The information processing apparatus according to claim 1 , wherein the predetermined substance is a bone or fat.

7. The information processing apparatus according to claim 1 , wherein the at least one of (a) one or more processors and (b) circuitry is configured to further perform providing a user interface for a user to select the predetermined substance from a plurality of substances that include a bone and fat.

8. The information processing apparatus according to claim 1 , wherein the at least one of (a) one or more processors and (b) circuitry is configured to further perform generating image data representing the remaining substance based on the effective atomic number of the remaining substance.

9. The information processing apparatus according to claim 8 , wherein the at least one of (a) one or more processors and (b) circuitry is configured to further perform displaying the image data on a display.

10. The information processing apparatus according to claim 8 , wherein the image data is a moving image.

11. The information processing apparatus according to claim 8 , wherein the at least one of (a) one or more processors and (b) circuitry is configured to further perform extracting a contrast agent, a medical device, or a lesion based on the image data.

12. A radiography system, comprising:

a radiation detector configured to obtain a radiation image based on radiation emitted onto an object;

an information processing apparatus comprising at least one of (a) one or more processors connected to one or more memories storing a program including instructions executed by the one or more processors and (b) circuitry configured to perform:

obtaining at least three radiation images from the radiation detector, each of the at least three radiation images corresponding to each of at least three types of energy; and

calculating, by separating a predetermined substance having a known attenuation coefficient in the object and a remaining substance other than the predetermined substance in the object based on the at least three radiation images, an effective atomic number of the remaining substance.

13. A radiography system, comprising:

a radiation detector configured to obtain a radiation image based on radiation emitted onto an object; and

an information processing apparatus configured to:

obtain at least three types of energy information from a plurality of radiation images obtained from the radiation detector;

calculate a thickness or an area density of a predetermined substance, based on the at least three types of energy information; and

calculate an effective atomic number for which the predetermined substance is excluded, based on the thickness or the area density of the predetermined substance.

14. An information processing method, comprising:

obtaining at least three radiation images based on radiation emitted onto an object, each of the at least three radiation images corresponding to each of at least three types of energy; and

calculating, by separating a predetermined substance having a known attenuation coefficient in the object and a remaining substance other than the predetermined substance in the object based on the at least three radiation images, an effective atomic number of the remaining substance.

15. A non-transitory computer-readable storage medium storing a program for causing a computer to execute an information processing method, comprising:

obtaining at least three radiation images obtained based on radiation emitted onto an object, each of the at least three radiation images corresponding to each of at least three types of energy; and

calculating, by separating a predetermined substance having a known attenuation coefficient in the object and a remaining substance other than the predetermined substance in the object based on the at least three radiation images, an effective atomic number of the remaining substance.