A CT apparatus without a gantry, comprising: a scanning passage; a stationary X-ray source arranged around the scanning passage and comprising a plurality of ray emission focal spots; a plurality of stationary detector modules arranged around the scanning passage and disposed opposite the X-ray source; and a detector arm comprising a transverse arm and a vertical arm; wherein the plurality of stationary detector modules comprise first detector modules mounted on the transverse arm and second detector modules mounted on the vertical arm; wherein central points of ray receiving surfaces of the first detector modules mounted on the transverse arm are located on a first straight line and central points of ray receiving surfaces of the second detector modules mounted on the vertical arm are located on a second straight line such as to be arranged substantially in an L-shape, and wherein the first straight line and the second straight line intersect at a point when viewed in a plane intersecting the scanning passage, characterized in that the CT apparatus further comprises a front collimator, wherein the front collimator is a correction grid disposed in front of the plurality of ray emission focal spots and between the plurality of ray emission focal spots and the detector modules for adjusting energies of ray beams from the ray emission focal spots, wherein the front collimator has an arrangement in a row or a plurality of rows corresponding to the ray receiving surfaces of the detector modules; wherein the ray emission focal spots are arranged in a row or a plurality of rows, and wherein a distance between the front collimator and the ray receiving surfaces of the detector modules is larger than a distance between the front collimator and the ray emission focal spots. a scanning passage; a stationary X-ray source arranged around the scanning passage and comprising a plurality of ray emission focal spots; a plurality of stationary detector modules arranged around the scanning passage and disposed opposite the X-ray source; and a detector arm comprising a transverse arm and a vertical arm; wherein the plurality of stationary detector modules comprise first detector modules mounted on the transverse arm and second detector modules mounted on the vertical arm; wherein central points of ray receiving surfaces of the first detector modules mounted on the transverse arm are located on a first straight line and central points of ray receiving surfaces of the second detector modules mounted on the vertical arm are located on a second straight line such as to be arranged substantially in an L-shape, and wherein the first straight line and the second straight line intersect at a point when viewed in a plane intersecting the scanning passage, characterized in that the CT apparatus further comprises a front collimator, wherein the front collimator is a correction grid disposed in front of the plurality of ray emission focal spots and between the plurality of ray emission focal spots and the detector modules for adjusting energies of ray beams from the ray emission focal spots, wherein the front collimator has an arrangement in a row or a plurality of rows corresponding to the ray receiving surfaces of the detector modules; wherein the ray emission focal spots are arranged in a row or a plurality of rows, and wherein a distance between the front collimator and the ray receiving surfaces of the detector modules is larger than a distance between the front collimator and the ray emission focal spots.