Calculated attenuation correction for awake small animal brain PET studies

Attenuation correction of small animal PET data is very important when quantitative images are of interest. Attenuation correction coefficients are conventionally obtained via a transmission or a computed tomography scan, which require anaesthetisation of the animal. However, in the context of awake and/or freely moving animals, where animal motion is compensated via appropriate motion tracking and correction techniques, anaesthetisation is no longer required. In this work we investigate the accuracy of a transmission-less attenuation correction approach based on the segmentation of the motion corrected emission image. Results on both phantom and real rat data acquired on the microPET Focus220 scanner, indicate good agreement between the segmentation based and conventional transmission based approach (~ 2% difference). In addition, the segmentation based approach has the potential to eliminate noise propagation from the measured transmission data to the reconstructed attenuation corrected emission images.