Fig 5. Brain SPECT designs. A, With a dual-head system, the acquisition time can be half that for a single-head camera. B, With a 3-head system, the acquisition time is reduced by a factor of 3. C, Four heads can be offset to allow large-FOV cameras to image close to the head. D, In a ring (helmet) detector, it is possible to rotate only the collimator inside the crystal and shielding.