object under the state where the fan beam position is controlled to the reference position application_number US 95615397 A description fig1 shows an x ray ct apparatus for executing x ray source position control according to one embodiment of the present invention an x ray tube 1 as an x ray source includes therein a rotary anode 1a and a filament 1b and is allowed to move its position in a direction represented by arrows of solid line or a direction represented by arrows of dotted line by a driving mechanism 6 the direction of the solid line or the dotted line is a slice width direction but is not a direction extending in a beam plane of a fan beam here the slice width direction and the beam plane of the fan beam orthogonally cross each other a collimator 3 is employed so as to convert the beams to the fan beam a multi channel detector 5 is so disposed as to oppose the x ray tube 1 while interposing a measurement space between them and rotates round the measurement space under this opposing state the x ray tube 1 the collimator 3 and the multi channel detector 5 are mounted into a rotary member referred to as an 34 x ray scanner 34 referring to fig1 the multi channel detector 5 represents only one channel and other channels are disposed in the depth wise direction of the sheet of the drawing in a multi channel configuration right and left end portions 5a and 5b are insensitive areas while a center 5c is a sensitive area in fig1 a center position p 0 of the detector is a reference fan beam position the phenomenon in which the center of the slice width 4 of the x.