Patent ID: 7203270

Claim:
An X-ray computed tomographic apparatus, comprising: an X-ray tube; a gantry configured to acquire projection data of an arbitrary range in a body axial direction of a subject by continuously moving a tabletop on which said subject is laid down and by continuously rotating said X-ray tube about said subject; a reconstructing portion configured to reconstruct image data from said acquired projection data according to reconstruction processing selected by an operator from plural types of reconstruction processing; and a tube current value determining portion configured to determine plural tube current values respectively corresponding to discrete, plural positions within said range, on the basis of said selected type of reconstruction processing and an image quality level specified or selected by said operator; wherein a particular tube current value, I b , is determined on the basis of SD (SDinput), mAs, PkV, Psl, PFW, PFC, SDa, t, PHP, Pmode, μ, DPa, and DPb, where SDa is an image SD of an image of a water phantom having a water equivalent thickness DPa used as the reference, taken and reconstructed with the use of a reference tube current, a reference tube voltage, a reference imaging slice thickness, and a reference image slice thickness, and a reference reconstruction function, SDinput is a desired image SD the operator wishes to obtain as the final image, mAs is a time-integrated tube current (sec) used as the reference, t is a scan speed (sec), PkV is a coefficient corresponding to a tube voltage, Psl is a coefficient corresponding to an imaging slice thickness, PHP is a coefficient corresponding to the helical pitch, PFW is a coefficient corresponding to a ratio of an image slice thickness with respect to an imaging slice thickness, PFC is a coefficient corresponding to a reconstruction function, Pmode is a coefficient corresponding to a normal mode or a low dose mode as to X-ray exposure, μ an X-ray absorption coefficient of water, DPa is a water equivalent thickness (mm) used as the reference, and DPb is a water equivalent thickness (mm) equivalent to the subject's body thickness.