For X-ray imaging systems, the effective radiation source is the machine itself. Figure 3 shows a typical layout while Figure 4 shows a better, more effective layout. Lead shielding requirements can be mitigated by placing equipment in larger rooms, effectively increasing the distance between the source of radiation and other occupied spaces. Care should be taken when locating the wall or chest bucky (the device used to hold film cassettes for chest X-rays taken in a standing position) in a radiographic room, since X-rays will strike this wall directly. In addition to increasing the distance, rooms adjacent to X-ray imaging systems of all kinds should be chosen for low-occupancy uses - storage rooms, janitor's closets, restrooms, and outdoor areas are all good choices to situate next to X-ray and CT rooms. Areas that have high occupancy, such as offices, nurses' stations, and so forth will require more shielding if placed in close proximity to an X-ray source


In imaging operations using radioactive material, the patient actually becomes the radiation source once injected with the radiopharmaceutical. This requires a different approach, as the source of radiation moves, occupies, and exposes different areas of the human body. For SPECT and general nuclear medicine imaging, this is less of a concern because the emitted radiation is not very penetrating. However, for PET and PET/CT suites, the site planner should consult closely with the radiation physicist at the layout stage. For these suites, the PET/CT scan room is typically not the most critical shielding design element. Rather, the "uptake" or "quiet" rooms, where the patients wait for 30-60 minutes between the radiopharmaceutical injection and the scanning procedure, are the major shielding concern. In a facility not laid out with this in mind, the uptake room walls can require several inches of lead thickness to provide adequate shielding to an adjacent office or waiting room. Of course, for a PET/CT suite, the scan room must be analyzed and shielded as a CT scanner room in addition to the shielding required due to the PET radioactive material.

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