A radiation shield is fixed to scanning equipment at a location that attenuates a moving beam of radiation only while the beam passes over a relatively vulnerable portion, especially anterior portion, of the patients body. Such an in-plane shield can be selective as to radiation wavelength attenuation. As an example, for scanners that use X-rays, the low energy portion of the spectrum can be selectively blocked while the high energy portion of the spectrum passes through to the patient and detector. When embodied in a CT X-ray scanner, the selective attenuation can be achieved with a thin slice bismuth shield/filter permanently installed on at least the anterior quadrant of the gantry, preferably on a span of approximately about 140 deg. in registry with the circular path of the source.
