Continuous bed motion acquisition for an LSO PET/CT scanner

Standard whole-body PET/CT protocols collect PET emission data for a sequence of discrete, overlapping bed positions. An alternative acquisition mode in which the patient bed moves continuously through the scanner has some significant advantages, including uniform axial signal-to-noise, elimination of resolution artifacts by sampling continuously in the axial direction, and a reduction in both noise from detector normalization and artifacts from small patient movements. To validate this approach, continuous bed motion acquisition has been implemented on a high resolution, 16-slice LSO PET/CT scanner (CPS Innovations, Knoxville, TN). The emission data are acquired in list mode with the bed moving at a constant velocity in the range 0.3-0.7 mm/s for a total scan time in patients of around 20 minutes covering an axial extent of 36-84 cm. The absolute position of the bed is read and inserted directly into the list mode data stream. Following acquisition, the emission data are rebinned into a fully 3D data set and reconstructed using a 3D OSEM algorithm. Continuous movement of the patient bed yields uniform signal-to-noise throughout the axial imaging field. For short imaging times, the bed movement in the standard acquisition becomes a significant fraction of the total scan time and continuous bed motion acquisition offers a more efficient alternative. Results are presented for some representative patient studies with both step-and-shoot and continuous bed motion acquisition.