Event-based motion correction in PET transmission measurements with a rotating point source

Accurate attenuation correction is important for quantitative positron emission tomography (PET) imaging. In PET transmission measurement using external rotating radioactive sources, object motion during the transmission scan can affect measured attenuation correction factors (ACFs), causing incorrect radiotracer distribution or artefacts in reconstructed PET images. Therefore a motion correction method for PET transmission data could be very useful. In this paper we report a compensation method for rigid body motion in PET transmission measurement, in which transmission data are motion-corrected event-by-event, based on known motion, to ensure that events that traverse the same path through the object are recorded on the same LOR. After motion correction, events detected on different LORs may be recorded on the same transmission LOR. To ensure that the corresponding blank LOR records events from the same combination of contributing LORs, the list mode blank data are spatially transformed event-by-event based on the same motion information. The proposed method has been verified in phantom studies with continuous motion.