Method and system for allowing imaging of any size object through use of separate source and detector unit

A tomographic apparatus comprising:

• radiation means having a radiation generating point for providing a radiation beam;
• sensor means having a radiation sensor for sensing the intensity of said radiation beam to provide radiation absorption data, a space being provided between said radiation means and said sensor means such that an object to be inspected by the tomographic apparatus may be inserted therein, said radiation means and said sensor means being separate units with the distance therebetween being variable;
• detector means, coupled to said radiation means and sensor means, for detecting a prescribed geometrical relationship between said radiation generating point and said radiation sensor;
• and
• reconstructor means, coupled to said detector means, for reconstructing CT image data from said radiation absorption data in accordance with the detected geometrical relationship between said radiation generating point and said radiation sensor;
• scan means, coupled to said radiation means, for shifting said radiation generating point so that said radiation beam scans said object, wherein said prescribed geometrical relationship is that a locus of points defined by shifting said radiation generating point is substantially parallel to an arrangement of radiation sensing elements of said radiation sensor;
• wherein said radiator means and said sensor means are associated with parallel adjust means for effecting such an adjustment that a linear line between two given points along the locus of said radiation sensing point is in parallel to a linear line between other two given points along the arrangement of radiation sensing elements of said radiation sensor.

A tomographic apparatus comprising:

• radiation means having a radiation generating point for providing a radiation beam;
• sensor means having a radiation sensor for sensing the intensity of said radiation beam to provide radiation absorption data, a space being provided between said radiator means and said sensor mean such that an object to be inspected by the tomographic apparatus may be inserted therein, said radiation means and said sensor means being separate units with the distance therebetween being variable;
• detector means, coupled to said radiation means and sensor means, for detecting a prescribed geometrical relationship between said radiation generating point and said radiation sensor;
• and
• reconstructor means, coupled to said detector means, for reconstructing CT image data from said radiation absorption data in accordance with the detected geometrical relationship between said radiation generating point and said radiation sensor;
• wherein said reconstructor means includes:
• means for calculating an estimation function J[.mu.(x,y)] of said CT image data with respect to an x-y plane on which said radiation beam passes, said estimation function J[.mu.(x,y)] being defined as:
• ##EQU17## wherein n denotes the position of said radiation generating point, m denotes the position of one of radiation sensing elements contained in said radiation sensor, w(m,n) denotes a given weight function, .tau.m(m,n) corresponds to said radiation absorption data, and .tau[mu.(x,y):m,n] is represented by:
• ##EQU18## wherein .PSI. is a given function of the intensity of said radiation beam;
• means for calculating a gradient g[.mu.(x,y):x,y] of said estimation function J[.mu.(x,y)] according to the following relation:
• ##EQU19## means for calculating an image correcting direction S.sub.i (x,y) according to the following relation:
• S.sub.i (x,y)=g[.mu.(x,y):x,y]+F.multidot.S.sub.i-1 (x,y)
• wherein F denotes a function of g[.mu..sub.1 (x,y):x,y] and g[.mu..sub.i-1 (x,y):x,y], g[.mu..sub.i (x,y):x,y] denotes a gradient of said estimation function with respect to the ith iterated image, and g[.mu..sub.i-1 (x,y):x,y] denotes a gradient of said estimation function with respect to the (i-1)th iterated image.