Image diagnostic device and an image diagnostic method for automatic assessment of the start and end of the inflow of a contrast medium

1. An image diagnostic device that evaluates a bloodstream dynamic state of a subject, the device comprising:

an image acquisition unit configured to acquire an image on a basis of a signal received from a subject;

an assessment unit configured to:

approximate a shape of a time intensity course with an S-shaped function to create a model function, and

automatically assess a start and end of an inflow of a contrast medium on a basis of the shape of the time intensity course representing time changes of a brightness of the image, wherein the assessment of the start and end of the inflow of the contrast medium is further based on an inflection point of the model function; and

a display unit configured to display a result assessed by the assessment unit.

2. The image diagnostic device of claim 1 , wherein the assessment unit is further configured to perform a fitting process such as a least-square method that is generally used as an approximate process for the time intensity course using the S-shaped function.

3. The image diagnostic device of claim 1 , wherein the assessment unit is further configured to calculate a time near an inflection point using a maximum value of a function in which a temporal differentiation process is performed for the time intensity course in an approximate process.

4. The image diagnostic device of claim 1 , wherein the assessment unit is further configured to calculate a time near an inflection point using a frequency distribution of the time intensity course in an approximate process.

5. The image diagnostic device of claim 1 , further comprising an external input unit configured to input a time near an inflection point of the time intensity course for the time intensity course displayed on the display unit in an approximate process.

6. The image diagnostic device of claim 1 , wherein the assessment unit is further on configured to assess the start and end times of the inflow of the contrast medium on a basis of intersection points of a tangent line at an inflection point of the model function and asymptotic lines provided above and under the model function, or on a basis of a frequency distribution of the time intensity course.

7. The image diagnostic device of claim 1 , further comprising an external input unit, wherein the display unit is further configured to display the model function, the inflection point of the model function, and the inclination of the tangent line, and wherein the external input unit can finely tune the inflection point and the tangent line of the model function displayed on the display unit.

8. The image diagnostic device of claim 1 , wherein in a case where the contrast medium flows in through multiple stages, the assessment unit is further configured to create the model function using a function obtained by linearly combining the plural S-shaped functions to be obtained.

9. The image diagnostic device of claim 1 , wherein the display unit is further configured to display the time intensity course representing the time changes, the model function created by the assessment unit, the image information from the image acquisition unit, and the start and end times of the inflow of the contrast medium assessed by the assessment unit.

10. The image diagnostic device of claim 1 , wherein the assessment unit is further configured to create the time intensity course after space and time average processes are performed for the image from the image acquisition unit.

11. The image diagnostic device of claim 1 , the display unit is further configured to display the image information acquired from the image acquisition unit at the start and end times of the inflow of the contrast medium assessed by the assessment unit.

12. The image diagnostic device of claim 1 , further comprising an operation unit configured to operate an averaging or maximizing brightness of the image information acquired from the image acquisition unit.

13. An image assessment method to evaluate a bloodstream dynamic state of a subject, comprising:

acquiring, by an image acquisition unit, an image on a basis of a signal received from a subject;

approximating, by an assessment unit, a shape of a time intensity course with an S-shaped function to create a model function;

automatically assessing, by the assessment unit, a start time and end time of an inflow of a contrast medium on a basis of a shape of a time intensity course representing time changes of a brightness of the image, wherein the assessment, by the assessment unit, of the start and end of the inflow of the contrast medium is further based on an inflection point of the model function; and

displaying, by a display unit, a result assessed by the assessment unit.