Apparatus for minimizing radiation exposure and improving resolution in radiation imaging devices

Claim 1

In a tomographic patient imaging apparatus of the type wherein photons emitted by a radiation source through an aperture means, the dimensions of which define a boundary of the desired beam to be projected, are caused to pass in a beam at different angles and directions through a thin slice or section of the patient and be at least partially attenuated and absorbed thereby, with the intensity of the emerging beam being detected and measured in a detector means so as to obtain signals representative of the absorption coefficients and density of the slice, said signals being manipulated by a computer whereat the image of said slice is reconstructed, said reconstructed image thereafter being displayed, the improvement of a collimating apparatus disposed adjacent the radiation source and defining means for projecting towards the patient a penetrating beam of radiation which is substantially non-diverging from said defined boundary in at least one direction to minimize radiation exposure to the patient outside the area of the selected thin slice, said collimating apparatus comprising an elongated sandwich assembly of a plurality of layers of material exhibiting relatively high radiation attenuation characteristics, said attenuating layers being spaced apart and separated from one another by interleaved layers of material exhibiting relatively low radiation attenuation characteristics, said sandwich assembly being disposed in a lengthwise manner adjacent the aperture means in the path and throughout the defined boundary of the radiation emitted through the aperture means, such that said attenuating layers are parallel to the desired direction of the projected beam with said interleaved spacing layers providing multiple direct paths for the radiation comprising the projected beam.