X-ray CT apparatus and reconstruction processing apparatus

1. An X-ray CT apparatus comprising:

an X-ray tube configured to generate X-rays;

a photon counting detector including a plurality of detecting elements each configured to output a signal in response to any of the X-rays becoming incident thereto after having passed through an examined subject; and

processing circuitry configured to:

determine, within a reconstruction region, a first region on which a spectrum reconstructing process is to be performed and a second region on which an energy integral reconstructing process is to be performed, on a basis of output values related to energy spectra based on signals output by the detecting elements; and

generate an image on a basis of the determined first region and the determined second region.

2. The X-ray CT apparatus according to claim 1 , wherein

the processing circuitry calculates the output values for each of views and judges, for each of the views, whether or not the calculated output values are each equal to or larger than a threshold value, and

with respect to each of positions included in the reconstruction region, the processing circuitry determines the first region and the second region on a basis of judgment results regarding the views going through the position.

3. The X-ray CT apparatus according to claim 2 , wherein, with respect to each of the positions included in the reconstruction region, the processing circuitry determines the position to be in the first region when the output values corresponding to all the views going through the position are each smaller than the threshold value.

4. The X-ray CT apparatus according to claim 2 , wherein

with respect to each of the positions included in the reconstruction region, the processing circuitry determines the position to be in the first region when, among all the views going through the position, the output values corresponding to views in such a quantity that make a half reconstruction process possible are each smaller than the threshold value, and

the processing circuitry generates a first image corresponding to the first region by performing the half reconstruction process.

5. The X-ray CT apparatus according to claim 2 , wherein

from among the views of which the output values are determined to be equal to or larger than the threshold value, the processing circuitry determines a position including a view that makes a spectrum reconstructing process possible when the output value thereof is corrected, to be in a third region, and

after correcting the output values in the third region, the processing circuitry generates a third image corresponding to the third region by performing the spectrum reconstructing process.

6. The X-ray CT apparatus according to claim 2 , wherein, within the reconstruction region, the processing circuitry determines such a region that is positioned outside a view of which the output value is determined to be equal to or larger than the threshold value, to be the second region.

7. The X-ray CT apparatus according to claim 1 , wherein the processing circuitry determines a region having either a circular shape or an oval shape, to be the first region.

8. The X-ray CT apparatus according to claim 1 , wherein the processing circuitry further causes a first image corresponding to the first region to be displayed as being superimposed over a second image corresponding to the second region.

9. The X-ray CT apparatus according to claim 8 , wherein the processing circuitry causes the first image corresponding to the first region and the second image corresponding to the second region to be displayed in such a manner that the first and the second images are distinguishable from each other.

10. The X-ray CT apparatus according to claim 1 , wherein the processing circuitry calculates total output values of counts of energy bins as the output values.

11. The X-ray CT apparatus according to claim 1 , wherein the processing circuitry calculates pile-up count values of counts of energy bins as the output values.

12. The X-ray CT apparatus according to claim 1 , wherein the processing circuitry calculates energy integral values of representative values of energy bins as the output values.

13. The X-ray CT apparatus according to claim 1 , wherein the processing circuitry calculates pile-up energy integral values of representative values of energy bins as the output values.

14. A reconstruction processing apparatus comprising processing circuitry configured to:

obtain output values related to energy spectra based on signals output from a plurality of detecting elements included in a photon counting detector and each configured to output a signal in response to X-rays becoming incident thereto after having passed through an examined subject;

determine, within a reconstruction region, a first region on which a spectrum reconstructing process is to be performed and a second region on which an energy integral reconstructing process is to be performed, on a basis of the output values; and

generate an image on a basis of the determined first region and the determined second region.

15. An X-ray CT apparatus comprising processing circuitry configured to:

calculate output values related to energy spectra from an imaging planning-purpose image obtained by imaging an examined subject while using X-rays; and

determine a spectrum reconstruction possible region corresponding to the examined subject, on a basis of the output values related to the energy spectra and to cause a display to display the spectrum reconstruction possible region.

16. The X-ray CT apparatus according to claim 15 , wherein

the processing circuitry further receives, from an operator, a setting regarding the spectrum reconstruction possible region that was speculated, and

the processing circuitry identifies a parameter used when the set spectrum reconstruction possible region is scanned and causes a display to display the identified parameter.

17. The X-ray CT apparatus according to claim 16 , wherein

the processing circuitry receives, from the operator, a setting to either enlarge or reduce the spectrum reconstruction possible region, and

in accordance with the enlargement of the spectrum reconstruction possible region, the processing circuitry sets the parameter so as to decrease an X-ray radiation dose per unit time period, whereas in accordance with the reduction of the spectrum reconstruction possible region, the processing circuitry sets the parameter so as to increase the X-ray radiation dose per unit time period.

18. The X-ray CT apparatus according to claim 15 , wherein the processing circuitry speculates two or more of the spectrum reconstruction possible regions, sets parameters used for newly scanning the spectrum reconstruction possible regions, and causes a display to display the speculated spectrum reconstruction possible regions and the parameters corresponding to the spectrum reconstruction possible regions.

19. The X-ray CT apparatus according to claim 15 , wherein

the processing circuitry calculates the output values in the imaging planning-purpose image for each of views and calculates output values corresponding to all the views on a basis of the calculated output values corresponding to each image, and

within the reconstruction region, the processing circuitry speculates such a region in which the output values corresponding to all the views are each equal to or smaller than a predetermined threshold value, to be the spectrum reconstruction possible region.

20. The X-ray CT apparatus according to claim 15 , wherein

the processing circuitry calculates the output values in the image for each of views and calculates output values corresponding to all the views on a basis of the calculated output values corresponding to each image, and

within the reconstruction region, the processing circuitry speculates such a region in which the output values corresponding to views in a certain range that make a half reconstruction process possible are each equal to or smaller than a predetermined threshold value, to be the spectrum reconstruction possible region.