X-ray CT apparatus

1. An X-ray CT apparatus comprising:

a body thickness information acquiring unit configured to acquire information of a body thickness of an object;

a threshold determining unit configured to determine a threshold of an exposure dose according to the body thickness of the object; and

an image generating unit configured to generate an image indicating a relationship between the body thickness of the object and the threshold, and superimpose the generated image on an image of the object.

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

a scanogram generating unit configured to generate a scanogram of the object,

wherein the body thickness information acquiring unit acquires a relationship between an area on a couch top and the body thickness of the object based on a scanogram of the object,

wherein the threshold determining unit determines the threshold of the exposure dose according to the body thickness of the object and determines a relationship between the area on the couch top and the threshold according to the body thickness of the object, and

wherein the image generating unit superimposes an image indicating the relationship between the area of the couch top and the threshold on the scanogram and displays the scanogram on a display unit.

3. The X-ray CT apparatus according to claim 2 , further comprising:

a plan acquiring unit configured to acquire information of a scan plan in which at least a relationship between an area on the couch top and an X-ray irradiation time is determined; and

a scan dose estimating unit configured to, before a scan based on the scan plan is performed, estimate a relationship between an area on the couch top and a radiation dose, the relationship being applied when the scan is performed,

wherein the image generating unit generates an image indicating the relationship between the area on the couch top and the radiation dose, the relationship being estimated by the scan dose estimating unit, and superimposes, on the scanogram, the image indicating the relationship between the area on the couch top and the radiation dose and the image indicating a relationship between the area of the couch top and the threshold to display the scanogram on the display unit before the scan based on the scan plan is performed.

4. The X-ray CT apparatus according to claim 3 , further comprising:

a dose history storage unit configured to, when a scan is performed, store a relationship between an area on the couch top and a radiation dose in the performed scan; and

a cumulative dose acquiring unit configured to, from the relationship stored in the dose history storage unit between an area on the couch top and a radiation dose of each scan, acquire a relationship between the area on the couch top and a historical cumulative radiation dose,

wherein the image generating unit generates an image indicating the relationship between the area on the couch top and the historical cumulative radiation dose and superimposes, on the scanogram, the image indicating the relationship between the area on the couch top and the image indicating the relationship between the area on the couch top and the threshold to display the scanogram on the display unit.

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

the plan acquiring unit acquires information of another scan plan after the scan based on the scan plan is performed,

the scan dose estimating unit estimates, before the scan based on the other scan plan is performed, a relationship between an area on the couch top and a radiation dose, the relationship being obtained when the scan is performed, and determines a cumulative dose obtained by adding the estimated dose and a historical cumulative radiation dose together, thereby estimating a relationship between an area on the couch top and the added cumulative dose, the relationship being obtained when the scan based on the other scan plan is performed, and

the image generating unit generates a first image indicating the relationship between the area on the couch top and the historical cumulative radiation dose, the relationship being estimated by the scan dose estimating unit and a second image indicating the relationship between the area on the couch top and the added cumulative dose, the relationship being obtained when the scan based on the other scan plan is performed, and superimposes, on the scanogram, the first image, the second image and the image indicating the relationship between the area on the couch top and the threshold to display the scanogram on the display unit before the scan based on the other scan plan is performed.

6. The X-ray CT apparatus according to claim 3 , further comprising a plan modification accepting unit configured to accept a modification of the scan plan,

wherein the scan dose estimating unit estimates, when a modification of the scan plan is accepted, before a scan based on a modified scan plan is performed, a relationship between an area on the couch top and a radiation dose, the relationship being applied when the scan is performed.

7. The X-ray CT apparatus according to claim 3 , wherein

the image generating unit generates, when there is an area on the couch top in which the radiation dose estimated by the scan dose estimating unit is likely to exceed the threshold, an image that issues a warning to that effect and superimposes the image that issues a warning on the scanogram.

8. A method for an X-ray CT apparatus, the method comprising:

acquiring information of a body thickness of an object;

determining a threshold of an exposure dose according to the body thickness of the object;

generating an image indicating a relationship between the body thickness of the object and the threshold; and

superimposing the generated image on an image of the object.

9. An X-ray CT apparatus comprising:

processing circuitry configured to

acquire information of a body thickness of an object,

determine a threshold of an exposure dose according to the body thickness of the object,

generate an image indicating a relationship between the body thickness of the object and the threshold, and

superimpose the generated image on an image of the object.