Radiographic apparatus

Apparatus for examining the body of a patient by means of penetrating radiation comprising:

• a. a ring-shaped locating structure adapted to enclose the part of the patient to be examined,
• b. a source of penetrating radiation,
• c. a detecting means sensitive to the radiation,
• d. a scanning structure, which is rotatable about an axis passing through the part of the patient enclosed by said locating structure, supporting said source and said detecting means so that the source can project radiation through the said part of the patient to be received by the detecting means,
• e. means for rotating said scanning structure about said axis so that the radiation can be projected through the body from a plurality of different directions in a plane substantially perpendicular to the said axis and,
• f. an attenuating mass not attached to and adapted to rotate around said locating structure on rotation of said scanning structure so as to present substantially the same profile to the radiation in the different positions of the scanning structure to compensate for changes in the absorbing path length presented to the X-rays by the body and locating structure during the scanning movement, wherein the locating structure is located in a fixed position during motion of the scanning structure.