X-ray CT apparatus, information processing device and information processing method

An information processing device comprising:

• processing circuitry configured to
• calculate an estimated spectrum based on an irradiation spectrum, an estimated length and information indicating a distortion of the spectrum occurring in a path of X-rays passing through a subject, the estimated spectrum being estimated as a spectrum after X-rays have passed through a subject, the irradiation spectrum being a spectrum before reaching the subject among spectra indicating a distribution of number of photon counts for each energy of X-rays irradiated to the subject from an X-ray generator, the estimated length representing an estimated value of an X-ray transmission length of a material of decomposition target,
• determine the X-ray transmission length of the material of decomposition target based on the estimated spectrum and a detected spectrum of X-rays detected on an X-ray detector detecting X-rays having passed through the subject,
• calculate an error between the estimated spectrum and the detected spectrum based on a difference between the detected spectrum and the estimated spectrum in number of photon counts for each energy, and based on a weighting coefficient corresponding to an energy based on a characteristic of the material, the weighting coefficient for an energy with an energy difference from an energy corresponding to a K-edge not exceeding a first threshold being smaller than weighing coefficients of other energies, wherein
• the X-ray transmission length of the material is determined based on the calculated error.

An information processing method performed by processing circuitry, the method comprising:

• calculating an estimated spectrum based on an irradiation spectrum, an estimated length and information indicating a distortion of the spectrum occurring in a path of X-rays passing through a subject, the estimated spectrum being estimated as a spectrum after X-rays have passed through a subject, the irradiation spectrum being a spectrum before reaching the subject among spectra indicating a distribution of number of photon counts for each energy of X-rays irradiated to the subject from an X-ray generator, the estimated length representing an estimated value of an X-ray transmission length of a material of decomposition target,
• calculating an error between the estimated spectrum and a detected spectrum based on a difference between the detected spectrum and the estimated spectrum in number of photon counts for each energy, and based on a weighting coefficient corresponding to an energy based on a characteristic of the material, the weighting coefficient for an energy with an energy difference from an energy corresponding to a K-edge not exceeding a first threshold being smaller than weighing coefficients of other energies, and
• determining an X-ray transmission length of the material of decomposition target based on the calculated error, the estimated spectrum, and the detected spectrum, the detected being a spectrum of X-rays detected on an X-ray detector detecting X-rays having passed through the subject.