Implementation of true continuous bed motion in 2-D and 3-D whole-body PETscanning

True continuous axial bed motion has been implemented on a high-resolution positron emission tomography (PET) scanner for use in both two-dimensional (2-D) and three-dimensional (3-D) acquisition modes. This has been accompli shed by modifications in the bed motion controller firmware and by acquirin g data in list mode. The new bed controller firmware was shown to provide a n accurate and constant bed speed down to 0.25 mm/s with a moderate patient weight load. The constant bed motion eliminates previously reported dead-t ime due to bed positioning when using small discrete bed steps. The continu ous bed motion was tested on uniform phantoms, in 2-D and 3-D. As a result of the continuous axial motion, a uniform axial sensitivity is achieved. Th is was also reflected in the reconstructed images, which showed an improvem ent in axial image uniformity (1.4% for continuous sampling, 5.0% for discr ete) as well as an improvement in %SD uniformity in comparison to conventio nal step-and-shoot acquisitions. The use of the continuous axial motion als o provide slight improvements in 2-D emission and transmission scanning, re sulting in an overall improved image quality in whole-body PET.