Continuous bed motion (CBM) uniform sensitivity emission image with partially known axial attenuation information, available from CT scans

2083 Objectives In PET-CT, the axial length of image reconstruction is defined by the CT scan, which delivers an axial extend-dependent dose of radiation. Still the CBM acquisition results in over-scanning, where more data are acquired than are needed to reconstruct targeted volumes of interest. The end planes will have lower sensitivity due to the absence of oblique LOR attenuation factors. Nevertheless, recent investigations concluded that both activity and attenuation distributions can be obtained from PET emission TOF data alone. The maximum-likelihood activity and ACF estimation (MLACF) iterative algorithm reconstructs the emission image, with estimation of partially unknown ACFs. Methods The patient data were acquired in the list mode file on a Siemens mCT scanner. The patient was scanned with 1mm/s bed speed. The full 44 cm CT volume was acquired but it was assumed that axially short (PET scanner length, 22 cm) CT volume would be known. The CBM PET sinogram was generated where direct PET planes, corresponding to 22 cm CT volume, had axially uniform sensitivity. This led to over-scanning and the use of additional data resulted in 44 cm extended PET volume. Three images were generated. One was a gold standard OSEM reconstruction, where full 44 cm CT information was used. Another was MLACF reconstruction, where only known 22 cm CT information was used. Both reconstructions resulted in extended PET volume and part of the image, 22 cm uniform sensitivity PET volume corresponding to the short CT volume, was extracted. The third image was OSEM reconstruction of the short 22 cm PET volume. Results The MLACF resulted in slower convergence of end planes. However, they are of similar quality to the gold standard, while the OSEM reconstruction (shorter volume) showed degraded end planes. Conclusions The known CT volume can be effectively and theoretically exactly extended in the axial direction, based on available emission data. This leads to clinically useable CBM PET image end planes.