Design of a nested SPECT-CT system with fully suspended CT sub-system for dedicated breast imaging

A fully suspended, stand-alone cone beam CT system capable of complex trajectories, in addition to a simple circular trajectory, has previously been developed and shown to minimize cone beam sampling insufficiencies and have better sampling close to the chest wall for pendant breast CT imaging. A hybrid SPECT-CT system with SPECT capable of complex 3D trajectories has already been implemented and is currently in use. Here, the individual systems are redesigned into one hybrid system where each individual component is capable of traversing independent, arbitrary trajectories around a pendant breast and anterior chest wall in a common field of view. The integration also involves key hardware upgrades: a new high resolution 40x30cm2 flat panel CT imager with an 8mm bezel on two sides for closer chest wall access, a new x-ray source, and a unique tilting mechanism to enable the spherical trajectories for CT. A novel method to tilt the CT gantry about a 3D center of rotation is developed and included in the new gantry, while preserving the fully-3D SPECT system nested within the larger CT gantry. The flexibility of the integrated system is illustrated.