According to the present invention, a base material thickness projection estimation value (124) and a base material thickness projection estimation error value (125) are estimated for M (M≤N) pieces of base materials on the basis of measured count projection values (121) obtained through N energy windows of a subject; and the base material thickness projection estimation value (124) is updated so as to increase the likelihood, based on the concurrent probability density, of all X-ray projection paths based on the base material thickness projection estimation error value (125), and then a resultant base material thickness projection second assumption value (127) is back-projected to obtain a base material density image estimation value (128).
展开▼
